j ourna l ho me page: www.elsev ier .com/ locate /ysmim
eview
acrophages and cellular immunity in Drosophila melanogaster
atrina S. Goldb, Katja Brücknera,b,c,∗
Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell ResearchDepartment of Cell and Tissue BiologyCardiovascular Research Institute, University of California San Francisco, San Francisco, CA, United States
r t i c l e i n f o
rticle history:eceived 7 September 2015ccepted 8 January 2016vailable online 23 April 2016
The invertebrate Drosophila melanogaster has been a powerful model for understanding blood cell devel-opment and immunity. Drosophila is a holometabolous insect, which transitions through a series of lifestages from embryo, larva and pupa to adulthood. In spite of this, remarkable parallels exist betweenDrosophila and vertebrate macrophages, both in terms of development and function. More than 90% ofDrosophila blood cells (hemocytes) are macrophages (plasmatocytes), making this highly tractable geneticsystem attractive for studying a variety of questions in macrophage biology. In vertebrates, recent find-ings revealed that macrophages have two independent origins: self-renewing macrophages, which resideand proliferate in local microenvironments in a variety of tissues, and macrophages of the monocyte lin-eage, which derive from hematopoietic stem or progenitor cells. Like vertebrates, Drosophila possessestwo macrophage lineages with a conserved dual ontogeny. These parallels allow us to take advantage ofthe Drosophila model when investigating macrophage lineage specification, maintenance and amplifica-tion, and the induction of macrophages and their progenitors by local microenvironments and systemiccues. Beyond macrophage development, Drosophila further serves as a paradigm for understanding themechanisms underlying macrophage function and cellular immunity in infection, tissue homeostasis andcancer, throughout development and adult life.
The blood cell system of the invertebrate Drosophilaelanogaster comprises two myeloid lineages, which shareighly conserved features with the vertebrate myeloid systemsFig. 1). Unlike vertebrates, Drosophila lacks both a lymphoidystem and red blood cells for oxygen transport, the latter insteadeing achieved by an extensive tracheal system. Drosophila largelyelies on innate immunity, encompassing both a humoral responsef antimicrobial peptide expression, and cellular responses ofhagocytosis and encapsulation. In Drosophila, the major class oflood cells, or hemocytes, are plasmatocytes, which are consideredquivalent to vertebrate macrophages. At every developmentaltage, aside from the early embryo, more than 90% of all hemocytesre plasmatocytes [1–3], which have important functions duringnimal development, and in response to infection, tissue damage,nd tumor growth.
. Macrophage lineages and development in Drosophila
.1. Self-renewing macrophages of embryonic origin
Recent work has shown that, in vertebrates, there are twoevelopmentally independent lineages of macrophages [4–9]. Theyerive (1) from erythro-myeloid progenitors (EMPs) of the yolkac [10,11] and (2) from hematopoietic stem and progenitor cellsHSPCs) of the bone marrow, via differentiation into monocytes12,13] (Fig. 1). EMP-derived macrophages colonize a multitudef organs during development and continue to self-renew inocal microenvironments; they are therefore known as tissue-esident macrophages [8,14–16]. Just like in vertebrates, Drosophilaas a lineage of macrophages (plasmatocytes) that colonize tis-ues and self-renew in local microenvironments [17–19]. Theseacrophages originate from the procephalic (head) mesoderm of
he embryo, which gives rise to a defined number of blood cell pro-enitors, also called prohemocytes [3] (Figs. 1 and 2). More than0% of these prohemocytes differentiate into ∼600 plasmatocytes,hich have macrophage-like roles in the removal of pathogens
nd apoptotic cells [3], and the deposition of extracellular matrixuring development [20]. A small percentage of embryonic pro-emocytes develop into crystal cells, a specialized blood cell typehat catalyzes melanization reactions in response to wounding andathogen invasion [21], and shares features with vertebrate gran-locytes.
Many studies have dissected the factors that determine theate of prohemocytes and promote their differentiation into plas-
atocytes or other blood cell types. For example, several highlyonserved transcription factors specify blood cell lineages duringrosophila embryogenesis. The GATA factor Serpent (Srp) is bothecessary and sufficient for hemocyte specification in the embry-nic mesoderm [22], acting upstream of the transcription factorsozenge (Lz), Glial cells missing (Gcm) and U-shaped (Ush) [21,23].cm [24,25] and Gcm2 [26] have redundant roles in specifying the
lasmatocyte lineage in the embryo, while the Runx protein Lz [21],hich is the Drosophila orthologue of Acute Myeloid Leukemia-
, is required for crystal cell specification. U-shaped, a zinc fingerriend of GATA (FOG) protein, acts to suppress crystal cell formation
[23,27]. The regulation and function of these transcription factorsare reviewed in more detail elsewhere [19,28,29].
Plasmatocytes born in the Drosophila embryo colonize localmicroenvironments in the larva. This process is reminiscent ofthe colonization of fetal liver by EMPs in vertebrates, and thesubsequent colonization of multiple organs, including brain, lung,skin, heart, and pancreas, by EMP-derived tissue macrophages[10–16,30,31]. In particular, Drosophila plasmatocytes form sessile,or resident, clusters in specific areas of the gastrointestinal system(proventriculus) [32] and microenvironments in the larval bodywall (Hematopoietic Pockets) that form a segmentally repeatedand terminal segment pattern [17,18] (Figs. 1 and 2). This popu-lation of plasmatocytes shows high rates of self-renewal, leadingto a >30-fold expansion of the macrophage pool, from about 300cells in the 1st instar to around 10,000 in the late 3rd instar [33,34].In the 1st larval instar nearly all hemocytes are resident, whereasan increasing number of hemocytes is found in circulation fromthe late 2nd larval instar onward, forming a steady state with theresident hemocyte population. Drosophila resident plasmatocytescan also give rise to two other types of blood cells: crystal cells[35,36] and, under immune challenge, lamellocytes [37], a type ofhemocyte specialized for the encapsulation of large foreign bodies,such as parasitoid wasp eggs. This suggests that at least some, ifnot all, plasmatocytes have lineage-restricted progenitor capacity,underscoring further parallels with vertebrate EMPs [31]. Severalstudies have reported distinct subpopulations of plasmatocyteswith varying combinations [37,38], and quantitative expression dif-ferences [17], of commonly used plasmatocyte “markers” such asHemolectin [39], Peroxidasin [40], P1 (Nimrod C1) [41], Croque-mort [42], Eater [43], and the pan-hemocyte marker Hemese [44].This favors the idea that specialized subsets of plasmatocytes exist,which could reflect the distinct functional capabilities of these cells.
Recent lineage tracing and live imaging experiments [17,35]have left little room for a scenario in which undifferentiated pro-genitors give rise to the resident and circulating hemocytes ofthe Drosophila larva, with the exception of the Lymph Gland (seeSection 2.2 below). Nevertheless, a small fraction of potentiallyundifferentiated, Wingless-positive Hemolectin-negative cells hasbeen reported among the resident/circulating hemocyte popula-tion [45], although their potential to expand and contribute to theblood cell pool remains to be investigated.
In the Drosophila Hematopoietic Pockets, sensory neuron clus-ters of the peripheral nervous system (PNS) serve as inductivemicroenvironments for plasmatocytes/macrophages, linking envi-ronmental sensory inputs to the control of the macrophage pool([17] and Brückner lab, in revision). Activin-� produced by localneurons promotes plasmatocyte proliferation and adhesion (Brück-ner lab, in revision). This is consistent with ablation studies showingthat the PNS provides functional support to macrophages, pro-moting both their survival and localization [17]. The PNS is alsoknown to innervate the proventriculus [46], suggesting further con-nections between the nervous system and resident macrophagepopulations. In vertebrates, the nature and regulation of tissue
macrophage local microenvironments remain unknown. However,the anatomical juxtaposition of self-renewing macrophages andlocal populations of peripheral neurons, such as observed in the
K.S. Gold, K. Brückner / Seminars in Immunology 27 (2015) 357–368 359
Fig. 1. Ontogeny of macrophages in Drosophila and mouse development.(A) Two waves of hematopoiesis during Drosophila development. The embryonic/larval lineage (in red) originates from the embryonic head mesoderm (HM), differentiatesin the embryo, and subsequently expands in the larva as self-renewing tissue macrophages (plasmatocytes). The progenitor-based Lymph Gland lineage (in blue) originatesin the embryo and differentiates in the late larva. Macrophages of both lineages persist through pupal development into the adult.(B) Three waves of hematopoiesis during mouse development. The primitive wave (in green) emerges in the yolk sac and gives rise to the earliest macrophages; this lineagedoes not persist after birth. The wave of erythro-myeloid progenitors (EMPs, in red) also emerges in the yolk sac. These cells mature in the fetal liver, and colonize localm w and( colonm
sr
ameoiimd
ltlfvusfi
icroenvironments in various organs as tissue-resident macrophages that self-renemajor arteries) that gives rise to hematopoietic stem cells (HSCs in blue), which
acrophages.
kin [47,48] heart [49–51], and pancreas [52], suggest that similaregulatory relationships may exist.
Other components of the Drosophila Hematopoietic Pockets maylso have roles in regulating self-renewing macrophages. Larvaluscle layers, which line the internal side of the Hematopoi-
tic Pockets and on which plasmatocytes reside, are the sitesf JAK/STAT signaling after parasitoid wasp infection. Interest-ngly, this signaling activity is required for mounting a cellularmmune response against the parasite, and seems important for the
obilization of resident plasmatocytes into circulation, and theirifferentiation into lamellocytes [53].
The Hematopoietic Pockets of Drosophila also contain clusters ofiver-like oenocytes [17,18,54], evoking parallels with the localiza-ion of vertebrate EMPs and other blood cell progenitors to the fetaliver during development [10,31,55], and the residence of Kupf-er cells (self-renewing macrophages) in the liver throughout theertebrate lifespan [15,16]. However, the question of potential reg-latory roles requires further investigation in Drosophila; initial
tudies based on oenocyte fate suppression have failed to detect aunctional correlation between oenocytes and plasmatocyte local-zation [17].
persist. The definitive hematopoietic wave emerges from hemogenic endotheliumize the fetal liver and later the bone marrow, producing the monocyte lineage of
Self-renewing macrophage populations in vertebrates have spe-cific identities, based on their tissue of residence [56,57]. Tissuemacrophage populations play important roles in human diseaseand have started to become the focus of therapeutic interven-tions, as exemplified by pulmonary macrophage transplantation[58]. Thus, understanding the role of local microenvironments inthe regulation of progenitors and self-renewing macrophages isan important field of study that may provide a new interface, andmolecular targets, for clinical therapies and prevention.
2.2. Progenitor-derived macrophages of the Lymph Gland
The second lineage of Drosophila macrophages derives froma hematopoietic organ, the Lymph Gland (LG), largely through aprogenitor-based mechanism (Figs. 1 and 2). The Lymph Glanddevelops during larval stages, but it arises earlier, from an inde-pendent embryonic mesodermal anlage with the same origin asthe Drosophila heart-like organ, or dorsal vessel [2,59–61]. The
origin of Drosophila Lymph Gland progenitors from cardiogenicmesoderm echoes the origin of some vertebrate hematopoieticstem cells (HSCs) from a hemangioblast progenitor in the primi-tive streak, and HSCs from hemogenic endothelium of the aorta and
360 K.S. Gold, K. Brückner / Seminars in Immunology 27 (2015) 357–368
Fig. 2. Blood cell lineages in Drosophila.(A) The embryonic lineage of hemocytes (blood cells) with parallels to self-renewing tissue macrophages in vertebrates. Prohemocyte progenitors (blue) originate in theembryo and differentiate into plasmatocytes (macrophages, red) and a small number of crystal cells (orange); plasmatocytes are quiescent (q) until the end of embryogenesis.In the larva, plasmatocytes colonize local microenvironments, in particular the Hematopoietic Pockets, and expand by self-renewal. Plasmatocytes also give rise to a smallnumber of crystal cells and, upon immune challenge, lamellocytes (purple).(B) Lymph Gland hematopoiesis with parallels to progenitor-based hematopoiesis in vertebrates. Lymph Gland prohemocytes (blue) are specified from the cardiogenicmesoderm of the embryo. They proliferate at a low rate until the 2nd larval instar, then start differentiating, forming (1) intermediate progenitors and plasmatocytes (red),w urple)z mocyB here na
oLrccaofaopomttLml
lazeehr
hich expand further by proliferation; (2) crystal cells (orange); (3) lamellocytes (pone (MZ) of quiescent (q) progenitors, and a cortical zone (CZ) of differentiating heoth lineages of hemocytes are mobilized in the pupa and persist into the adult, wnd small numbers of crystal cells, but no lamellocytes, are present in the adult.
ther major arteries [29,55,62–64]. Prohemocytes of the Drosophilaymph Gland mature from the mid-2nd larval instar onward, givingise to an estimated ∼2000–3000 blood cells under non-immunehallenged conditions. More than 90% of these cells are plasmato-ytes, and the remainder consists of small fractions of crystal cellsnd lamellocytes [2,29,60]. By analogy to vertebrate macrophagesriginating from HSPCs, most Lymph Gland plasmatocytes deriverom undifferentiated progenitors [60,65]. In addition, differenti-ted Lymph Gland plasmatocytes undergo a relatively short phasef self-renewal, mainly in the 3rd instar larva [60,66,67]. A distinctopulation of intermediate progenitors that show combinationsf prohemocyte and plasmatocyte markers [68,69], or lack prohe-ocyte and plasmatocyte markers [70], and are more proliferative
han other cells, has been reported [69,70]; these cells are thoughto contribute to the pool of Lymph Gland plasmatocytes. Thusymph Gland plasmatocytes show similarities to HSPC-derivedacrophages of the monocyte lineage, which undergo limited pro-
iferation, particularly in response to immune challenges [71,72].The Lymph Gland is organized into several pairs of lobes
ocated at the anterior end of the dorsal vessel. The primary lobesre functionally regionalized into an undifferentiated medullaryone containing progenitors, sometimes distinguished by marker
xpression as pre-prohemocytes and prohemocytes, and a differ-ntiated cortical zone [60]. By 12 h after puparium formation, allemocytes have differentiated and the Lymph Gland disintegrates,eleasing its blood cells [73].
. The primary lobe of the differentiating Lymph Gland is organized into a medullarytes; differentiation of progenitors is completed by 12 h after puparium formation.ew blood cell production subsides and hemocyte numbers decline. Plasmatocytes
A large body of work has contributed to our understanding ofLymph Gland hemocyte differentiation, which is regulated by bothlocal and systemic signals. Several reports converge on a key rolefor the Posterior Signaling Center (PSC), which comprises a smallgroup of cells at the posterior end of the primary lobe. The PSC hasbeen proposed to act as supportive microenvironment, or niche,that maintains Lymph Gland prohemocytes in an undifferentiatedstate [66,74]. It has been reported that PSC cells send out severalmolecular cues to regulate the differentiation state of the LymphGland, including Serrate (Ser), Hedgehog (Hh), Wingless (Wg, Wnt),Decapentaplegic (Dpp, BMP) and Pvf1 (PDGF/VEGF-related factor)[59,66,68,74,75]. A recent study has challenged the roles of the PSCand Hedgehog signaling in maintaining progenitor maintenance[76], although, together with another study, it confirmed PSC func-tion in inducing lamellocyte differentiation upon parasitization[216,76]. Serrate expression and the consequent activation of Notchsignaling are required for crystal cell production [59] and maintain-ing the expression of Collier, a transcription factor which is highlyexpressed in PSC cells and has roles in the Lymph Gland response towasp infestation [67,76]. Wingless signaling has a dual role in theLymph Gland. It controls PSC cell number cell-autonomously, andis also active in medullary zone prohemocytes, where it is required
for progenitor maintenance [68]. Dpp antagonizes Wingless signal-ing in PSC cells, and is required cell autonomously to regulate thesize of the niche [75]. Pvf1 is required to maintain prohemocytes,although interestingly this signal is not received by progenitors
s in Im
izGlibi
mRwoo[g
2
dtsmecGsclorIptmltaitdclm[s
bdtaoInflm
3
alav[
K.S. Gold, K. Brückner / Seminar
n the medullary zone, but by differentiating cells in the corticalone. These cells in turn express the enzyme Adenosine Deaminaserowth Factor A (ADGF-A), which lowers extracellular adenosine
evels. Low adenosine leads to reduced Protein Kinase A (PKA) activ-ty and is thought ultimately to promote progenitor quiescencey stabilizing the active form of the transcription factor Cubitus
nterruptus (Ci) [77].In addition, Lymph Gland hematopoiesis is regulated by many
ore inputs, including the Hippo [78,79], JAK/STAT [80,81],el/NF�B-family related Toll [82] and FGFR [83] signaling path-ays, as well as the heparan sulfate proteoglycan (and Perlecan
rthologue) Trol [83,84], the germ line differentiation factor Bagf Marbles (Bam) [85,86], the zinc finger transcription factor Zfrp887], the GATA factor Pannier [81], and the Polycomb group (PcG)ene multi sex combs (mxc) [88].
.3. Macrophages in the pupa and the adult
Following their expansion and differentiation during larvalevelopment, the two Drosophila macrophage lineages persisthrough the pupal stage into the adult [89] (Fig. 2). At the tran-ition to pupariation, plasmatocytes and other blood cell types areobilized into circulation [17,73], a process which is promoted by
cdysone signaling [90]. From this point onward, the two bloodell lineages intermix, and distinguishing embryonic and Lymphland hemocytes is, according to current methodology, only pos-ible by lineage tracing. In the adult, plasmatocytes reside in orlose to a number of tissues, including fat body (which regu-ates metabolism and immunity) [93], heart [94,95,96,92]; gut [91],varies [38], respiratory (tracheal) system (Brückner lab in prepa-ation) and peripheral nervous system (Brückner lab unpublished).n addition, small numbers of crystal cells, but no lamellocytes, areresent in the adult [2,92,97]. The differentiation status and plas-icity of adult hemocytes is just beginning to be addressed, and
ay benefit from the development of Drosophila blood cell sub-ineage-specific antibodies and other hemocyte-specific researchools [41,43,98]. Recent findings indicate that functional subsets ofdult macrophages have distinct physiological and signaling rolesn immunity [99]. Notch signaling regulates crystal cell specifica-ion in the adult [92], which will be interesting to study in moreetail in the future, given that a transition from plasmatocyte torystal cell fate is also known to occur during the embryonic andarval stages of development [27,35,36,100]. Sex-specific factors
ay also influence the size and function of the adult blood cell pool101] and further study will provide more insight into the long-termurvival of Drosophila blood cells in males and females.
The proliferative capacity of adult plasmatocytes and otherlood cells has been a matter of debate. A recent report claimede novo production of hemocytes in the adult fly [92], whereashe majority of studies have not been able to obtain evidence ofdult hemocyte proliferation [2,38,97,102], even under a rangef immune-challenged conditions (Brückner lab in preparation).ndeed immunosenescence, involving a decline in both hemocyteumber and phagocytic function, has been documented as adulties age [101], and there is no evidence of homeostatic hemocyteaintenance [102].
. Macrophage functions in Drosophila
Macrophage functions in Drosophila include the removal ofpoptotic cells during development, the production of extracel-
ular matrix, and responses to immune invaders and damaged orberrant tissue. Many of these aspects show close parallels withertebrate systems, which have been reviewed in detail elsewhere19,29,103,104].
munology 27 (2015) 357–368 361
3.1. Macrophage functions in the embryo
In the Drosophila embryo, a major function of macrophages is theelimination of apoptotic cells [3], which is critical for development.Phagocytosis by Drosophila plasmatocytes requires scavengerreceptors such as Croquemort (Crq) [105], Draper [106,107], Eater[36,108] and other Nimrod family proteins [109,110], as well asadhesion molecules such as integrins [111]. In the embryo, phago-cytosis by macrophages is essential for remodeling the centralnervous system (CNS). Plasmatocytes phagocytose apoptotic neu-rons along the CNS midline, which ensures proper condensationof the nervous system [112,113] and is required for embry-onic survival. This has been demonstrated in Bicaudal-D andsrp mutants, which lack embryonic hemocytes [22,113,114], aswell as crq mutants and mutants of the receptor tyrosine kinasePvr (PDGF/VEGF Receptor) [113], in which embryonic hemocytesundergo premature apoptotic death [115]. In the embryonic tra-cheal system, macrophages have a similar role in the eliminationof apoptotic cells during tissue remodeling [116].
Embryonic plasmatocytes have important roles in the deposi-tion of extracellular matrix (ECM) components and the productionof ECM-associated molecules, including Collagen IV [20,117,118],Laminin [119], Tiggrin [120], Papilin [121], Peroxidasin [122,123],and �PS Integrin [124]. The importance of hemocyte-mediatedsculpting of the ECM has been demonstrated in the context ofnervous system development [125], the positioning of the renal(Malpighian) tubules [126], and the deposition of basal laminaesurrounding internal organs such as the brain and gut [20].
Macrophage functions in the Drosophila embryo typicallyinvolve regulated migration and invasion, such as their entryinto the posterior end of the embryo at germband extension[3,115,127], or their infiltration of the nerve cord at the ventralmidline [3,124,128]. Both systems have provided excellent oppor-tunities for addressing the cellular and molecular mechanisms ofmacrophage migration and invasion, as reviewed comprehensivelyelsewhere [129–131].
The Drosophila embryo has also proved fruitful for the studyof macrophage functions in response to injury, which is detailedthoroughly in many studies and reviews [40,130,132–135]. TheDrosophila embryo has further been used as a model for septicinjury (Fig. 3). At later stages, Drosophila embryos are competentto mount immune reactions, both through cellular mechanisms,involving phagocytosis by plasmatocytes [136], and humoralresponses via the induction of antimicrobial peptide expressionin the respiratory (tracheal) epithelium [137]. The competence ofthe respiratory epithelium to mount a humoral response is pro-moted by the steroid hormone ecdysone, which peaks at stage 12of embryogenesis [137].
3.2. Macrophage functions in the larva
The larval stage is the critical phase for the expansion andadaptation of the immune cell pool. Environmental, metabolic,infection- and injury-related signals impinge on a plethora ofsignaling pathways that regulate the two larval myeloid sys-tems, and in many cases lead them to mount a cellular immuneresponse (see also above and Ref. [19]). Embryonically derivedself-renewing macrophages (sometimes called ‘larval hemocytes’)are located in resident clusters close to barrier epithelia, particu-larly in the Hematopoietic Pockets beneath the epidermis [17,18],and around the proventriculus, an area of the gastrointestinal sys-tem that may act as a sink for bacteria and debris [32]. As the
larva matures, increasing numbers of self-renewing plasmatocytesdetach and enter into circulation [17,34,97], potentially monitor-ing the hemolymph for pathogens. Hemocytes of the Lymph Glandmature over the course of larval life, and are usually released into
362 K.S. Gold, K. Brückner / Seminars in Immunology 27 (2015) 357–368
Fig. 3. Innate immune responses in Drosophila.Throughout its life cycle, Drosophila can mount cellular and humoral innate immune responses. Cellular immune responses involve phagocytosis by plasmatocytes, melaniza-tion by crystal cells and lamellocytes, and encapsulation by lamellocytes. Humoral responses involve the induction of antimicrobial peptide (AMP) expression in a numberof tissues. In the larva, immune responses include the mobilization of resident plasmatocytes and their differentiation into lamellocytes, and the precocious differentiationand mobilization of Lymph Gland hemocytes. In the adult, hemocytes reside in proximity to tissues of innate immunity and barrier epithelia, such as the fat body (brown),respiratory epithelia (purple), gastrointestinal system (teal) and circulatory system (gray).
cea
3
tDotmorniwwlbita
atfiGg[
irculation only at the beginning of pupariation [60,73,97]. How-ver, upon immune or injury challenge, both hemocyte lineagesre mobilized into a cellular immune response (see below) (Fig. 3).
.2.1. Responses to sensory and metabolic stimuliIncreasing evidence suggests that environmental sensory detec-
ion impacts the regulation of the two myeloid lineages in therosophila larva. Linking sensory inputs, which signal beneficialr adverse environmental life conditions, with the expansion ofhe immune cell pool may be an important safeguard for the ani-
al to survive challenges, such as increased apoptotic cell death,r adapt to metabolic conditions. Environmental stimuli may beelayed to self-renewing macrophages through peripheral sensoryeuron clusters in the Hematopoietic Pockets [17,18] (Brückner lab
n revision). At these locations, sensory neurons are in direct contactith hemocytes and link neuronal activity to Activin� production,hich promotes macrophage adhesion and proliferation (Brückner
ab in revision). In the Lymph Gland, sensory inputs are linked tolood cell responses through systemic signals. Olfactory neurons
n the CNS produce the neurotransmitter GABA, which signals sys-emically to the Lymph Gland, where it triggers calcium signalingnd macrophage maturation [138].
Systemic signals also directly link the metabolic status of thenimal with regulation of the blood cell pool. For example, starva-ion drives the localization of plasmatocytes to the fat body [139], aat-storing tissue with roles in metabolism and immunity. Changes
n insulin signaling lead to the premature differentiation of Lymphland progenitors [69,139–141] and similar effects are also trig-ered by starvation, detected by the amino acid transporter Slimfast139]. Reactive Oxygen Species (ROS) levels in the Lymph Gland
respond to metabolic stress and Tor pathway activity [69,142], andexcessive ROS production stimulates precocious differentiation ofLymph Gland hemocytes [143].
3.2.2. Responses to parasitizationIn the Drosophila larva, a major model for studying cellular
immunity is infestation by parasitoid wasps, such as Leptopilinaboulardi [97,144,145]. In response to parasitization, self-renewingplasmatocytes mobilize rapidly into circulation from their residentsites, and differentiate into lamellocytes [37]. In a second waveresponse that occurs one or more days later depending on condi-tions such as temperature [37,67], hemocytes of the Lymph Glandundergo a burst of proliferation, differentiate precociously, and arereleased into circulation, thus acting as an emergency reservoir ofactive blood cells in the larva [97,144,146]. Under these conditions,cell signaling from the Posterior Signaling Center is required toinduce lamellocyte differentiation [74,76]. Hemocyte proliferationin the Lymph Gland after a parasitic challenge requires the systemicsteroid hormone ecdysone, explaining why 3rd but not 2nd instarlarvae can mount a Lymph Gland immune response [146]. The cel-lular immune response by hemocytes of both origins encompassesphagocytosis by plasmatocytes, encapsulation by lamellocytes, andmelanization by crystal cells and lamellocytes [147],
These responses often depend on a relay of signals, eithersystemically and/or through other tissues. [148]. For example, com-munication between hemocytes and larval muscle cells that line the
Hematopoietic Pockets has an important role in wasp egg encap-sulation. Parasitization triggers circulating hemocytes to secretethe cytokines Unpaired 2 (Upd2) and Unpaired 3 (Upd3) that acti-vate JAK/STAT signaling in somatic muscle, which is necessary for
s in Im
lJ[tsriwo[aHh
3
llebast(rsdtemrnbssodtibe
f[ibstb[
eSttto
teiti[
K.S. Gold, K. Brückner / Seminar
amellocyte formation and wasp egg encapsulation [53]. However,AK/STAT signaling alone is not sufficient to trigger encapsulation53]; other inputs are required in this process, such as the activa-ion of Toll signaling in the fat body [149]. Pathways such as JNKignaling drive lamellocyte formation [150,151], but their route ofelay remains to be investigated. The systemic peptide Edin, whichs expressed in the fat body upon wasp infestation, also induces
asp egg encapsulation, as well as mobilization and expansionf plasmatocytes, but not their differentiation into lamellocytes148]. Future investigation will show whether other tissues, suchs the liver-like oenocytes [17–19] or other components of theematopoietic Pockets, also have roles in relaying cellular andumoral immunity.
.2.3. Responses to infection and injuryA large body of work on cellular immunity in the Drosophila
arva has focused on intestinal infections. Here, hemocytes stimu-ate cellular and humoral immune reactions, the latter through thexpression of antimicrobial peptides (AMPs), which are inducedy the two major innate immune NF�B signaling pathways, Tollnd Imd [152]. Plasmatocytes in the larva function as phagocyticentinels combating microbial infection, for example in responseo gut infections induced by feeding on Serratia marcescensS. marcescens), which causes an Imd pathway-dependent localesponse [153]. Hemocytes also act as important cellular relays,ignaling to the fat body to coordinate immune responses acrossifferent tissues. For example, natural infection (feeding) byhe Drosophila pathogen Erwinia carotovora (Ecc15) induces AMPxpression in fat body, a response that is decreased in dominoutants lacking blood cells [154]. Hemocytes are thought to act as a
elay in a Nitric Oxide-induced systemic immune response to gram-egative infection, triggering Imd pathway activation in the fatody [155]. Similarly, hemocytes relay Ecc15-induced local stressignaling in the intestine, which is mediated by reactive oxygenpecies (ROS), to the fat body, where AMP expression is switchedn [156]. Defensin expression in the fat body depends on pathogenegradation in plasmatocytes, which requires the lysosomal pro-ein Psidin [157]. Bacterial infection also triggers AMP expressionn barrier epithelia, such as the respiratory system (trachea) [158],ut the involvement of hemocytes in this response remains to belucidated.
Using the Drosophila larva as a septic injury model has provedertile ground for studying innate immune responses to infection159–161]. Many of these studies have focused on the humoralmmune response, but there is also a cellular component mediatedy macrophages. Similarly to natural infections through the gut,eptic injury leads to the upregulation of antimicrobial peptides inhe larval fat body, and this response depends on a signal relayedy hemocytes through secretion of the Toll pathway ligand Spätzle162].
Cellular responses against bacteria provide an opportunity toxamine the phagocytic function of macrophages in more detail.everal studies have used larval hemocytes ex vivo to investigatehe function of phagocytic receptors, such as the scavenger recep-ors Eater [108] and Nimrod C1 [109], and other proteins, such ashe actin cytoskeleton regulators D-SCAR and Profilin, in the controlf bacterial phagocytosis [163].
Aseptic injury triggers a cellular immune response that includeshe mobilization of resident hemocytes, phagocytosis, and differ-ntiation into lamellocytes, recapitulating many aspects of septic
njury and parasitization [164]. Several studies have examinedhe cellular mechanisms of phagocytosis and encapsulation dur-ng aseptic injury [164,165], and are reviewed in detail elsewhere133,135].
munology 27 (2015) 357–368 363
3.2.4. Roles in ECM production and organ integrityPlasmatocytes in the larva continue to play important roles in
the production of ECM, which is crucial for organogenesis and organfunction. During larval development, hemocytes associate with thefemale gonad and secrete the ECM molecule Collagen IV (ColIV)[38]. These layers of ColIV are required during pupariation andadulthood to ensure proper molecular function of the germlinestem cell niche, and in turn, to regulate germline stem cell numberand homeostasis [38]. The possibility that macrophages regulateother stem cell microenvironments is tantalizing, and will be inter-esting to explore in the future.
3.3. Macrophage functions in the pupa
Drosophila undergoes pupariation and metamorphosis whenecdysone levels peak, signaling the end of larval development.Many larval tissues, which are often polyploid, are partially or com-pletely replaced by adult structures that arise from sets of imaginalcells or discs (e.g. eye, wing, and leg discs) [166]. Drosophilamacrophages have roles in the destruction and remodeling of theselarval tissues. For example, at the onset of metamorphosis, plas-matocytes associate with larval fat body cells and facilitate theirdegradation, a process that is continued well into the first week ofadult life [93]. Macrophages also participate in neuronal pruningat axons and dendrites [167], although a substantial part of thisprocess may be mediated by epidermal cells and glia [168,169].Macrophages facilitate the remodeling of many other structuresand organ systems, as exemplified by the maturation of wing discs,where hemocytes are required for the bonding of the dorsal andventral wing regions [170].
In the pupa, macrophages show less resident cluster forma-tion. Instead, they have been studied for their migratory anddynamic properties, which involve Integrin and other adhesion-related proteins [171], and are important for wound healing[172]. Macrophage motility and phagocytosis are also enhancedby ecdysone signaling [173]. Surprisingly, for the most partmacrophages may not be essential during pupariation and adult-hood. Animals with genetically ablated hemocytes are viable[174,175], although developmental defects have been found at lowpenetrance [174,176].
3.4. Macrophage functions in the adult
In the adult fly, plasmatocytes continue in their capacity asprofessional phagocytes, performing tissue repair [91,177–179],immune surveillance and defense (Fig. 3). Anatomically, hemocytesin the adult fly are found in close proximity to the fat body and manysurface epithelia, such as the respiratory (tracheal) epithelium andareas of the gastrointestinal system (Brückner lab in preparationand [91]) (Fig. 3). Clusters of hemocytes are also found in the dor-sal abdomen around the heart [92,94–96]. These accumulationsare thought to monitor and clear the hemolymph of pathogens,and have been reported in Drosophila and other invertebrates, suchas the mosquito Anopheles gambiae [96,99,180]. Classic inverte-brate literature described these hemocyte clusters as ‘invertebratephagocytic organs’ [181–183]. Indeed, recent publications on septicinjury models have highlighted the correlation between bacterialand particle accumulations around the heart, and correspondingmacrophage accumulations [94–96].
Many studies on the humoral immune response in adultDrosophila report associated roles for macrophages. Oral infectionwith S. marcescens triggers a dual immune reaction, comprising
a cellular immune response mediated by phagocytic plasmato-cytes, and a local intestinal antimicrobial response regulated bythe Imd pathway [153]. Signaling interactions between hemocytesand other tissues enable a coordinated immune response to be
3 s in Im
miLUigbsteiDosiaoo[nCelefdsriao[[toaottctatIeitmm
kSmtys
3r
ghdie
64 K.S. Gold, K. Brückner / Seminar
ounted in the adult fly, as seen in the larva. For example, septicnjury, or stimulation with the bacterial cell membrane componentPS (lipopolysaccharide), trigger expression of the cytokine ligandpd3 in adult macrophages, which activates JAK/STAT signaling
n the fat body, leading to the upregulation of immune responseenes [184]. Adult macrophages also respond to wounding andacterial infection through other growth factors, as exemplified byubpopulations of hemocytes that express the BMP ligand Dpp orhe Activin/TGF-� ligand Dawdle [99]. Antimicrobial peptides arexpressed in a variety of barrier epithelia in the adult fly, includ-ng Drosocin and Drosomycin in tracheal epithelia, Diptericin,efensin and Attacin in the gut, Metchnikowin and Defensin inral regions, Metchnikowin in renal tubules, and Cecropin, Dro-omycin and Defensin in reproductive tracts [185,186]. It will benteresting to investigate possible links between these responsesnd macrophage signaling. Considering the typically short durationf antimicrobial peptide expression [187,188], and recent findingsn the dual role of hemocytes in humoral and cellular immunity189], it appears likely that phagocytosis-mediated cellular immu-ity has an important role during the infection response in adults.onsistent with this hypothesis, inhibiting hemocyte function byxpressing a bacterial toxin (ExoS) that suppresses phagocytosiseads to increased sensitivity to bacterial infection [190]. Furthervidence of a role for cellular immunity in adult Drosophila comesrom TM9SF4 nonaspanin mutant flies, which have phagocytosis-efective hemocytes yet a seemingly unaffected AMP response, andhow increased lethality upon infection by gram-negative bacte-ia [191]. Blocking phagosome activity and bacterial degradationn adult flies leads to increased sensitivity to bacterial infection,s seen in mutants of full of bacteria, which encodes an orthologf a HOPS complex subunit necessary for vacuolar fusion in yeast96]. Adult macrophages require the phagocytic receptor Eater108], which is also required in hemocytes at earlier developmen-al stages and has specificity for gram-positive bacteria [36]. Lossf macrophages in the adult fly, induced either by targeted geneticblation or specific mutant backgrounds (e.g. domino), results notnly in a weakened immune response, but also in decreased long-erm survival after bacterial infection [174,175,192]. This suggestshat cellular immunity may have additional functions over theourse of infection, not just in the short-term. However, alterna-ive scenarios are possible, as it was recently shown that hemocyteblation leads to a shift in inflammation status, with an upregula-ion of Toll signaling and downregulation of the Imd pathway [176].nterestingly, adult macrophage responses may also be linked tonvironmental conditions. For example, phagocytosis and cellularmmunity appear to be regulated by circadian inputs, yet melaniza-ion responses and humoral immunity are not, as evidenced by a
odel of infection with the bacterial pathogen Streptococcus pneu-onia [193].
One controversial question in the field has been whether anyind of priming or adaptive immune response exists in Drosophila.ome reports suggested such phenomena, either through unknownolecular mechanisms or through alternatively spliced variants of
he cell surface molecule DSCAM [188,194]. However, future anal-sis will show whether additional mechanistic evidence for thesecenarios can be obtained [195].
.5. Macrophage functions in damage-induced tissueegeneration
Hemocytes promote damage-induced tissue recovery and tissuerowth at various developmental stages. Under certain conditions,
emocytes not only promote the regeneration of tissues, but alsorive their pathological overproliferation. Similarly, macrophages
n vertebrates play a host of vital roles in tissue repair and regen-ration, stimulating proliferation of damaged tissue and causing
munology 27 (2015) 357–368
hyperplasia or hypertrophy in some systems [196–199]. Drosophilaresearch has identified some of the molecular mechanisms under-lying these processes. For example, hemocytes play a key role in therecovery of the eye imaginal disc epithelium from tissue damageas a result of UV- and JNK-pathway-induced apoptosis. Damagedtissue switches on the transcriptional regulator Schnurri (Shn),leading to production of the PDGF/VEGF related ligand Pvf-1. Pvf-1in turn activates resident plasmatocytes, which limit further tissueloss [200]. During apoptosis-induced compensatory proliferationin imaginal epithelia, cells with elevated Caspase activity producereactive oxygen species (ROS) that induce the activation of residentplasmatocytes. These activated macrophages express the inflam-matory cytokine Tumor Necrosis Factor (TNF)/Eiger, which in turntriggers JNK signaling in the epithelial cells, leading to overpro-liferation [201]. In adult Drosophila, the regenerative response toinfection- or stress-induced gut injury, which often is associatedwith dysplasia, [202,203] depends both on the production of ROSby enterocytes [202,204] and the active involvement of hemocytes[91]. Intestinal tissue damage attracts plasmatocytes and stimu-lates them to produce BMP, which in turn triggers intestinal stemcell proliferation, resulting in gut dysplasia [91].
3.6. Macrophage functions in tumor biology
Drosophila is increasingly being used as a model for cancer[205,206]. Hemocytes participate in both the immune responseagainst tumors, and the promotion of tumor growth. Hemo-cytes are recruited to neoplastic tumors, which are often sites ofbasement membrane disruption, and thus bear some similaritiesto non-healing wounds or tissue damage challenges [207–209].Hemocytes adhere to epithelial tumors, and their numbers increasein response to tumor formation [208,209]. This is a consequenceof tumor-derived signals that stimulate the JAK/STAT or Pvrpathways in hemocytes [208,210]. When hemocytes mount animmune attack against tumors, a variety of responses can be seen,including phagocytosis, the induction of apoptosis, and melaniza-tion/encapsulation by crystal cells and lamellocytes, which isconsidered the functional equivalent to granuloma formation invertebrates [207,208,210].
As in vertebrates [211–213], the effects of macrophage recruit-ment and inflammation on tumor biology vary depending on thespecific genetic background and microenvironment of the tumor,and this warrants extensive future research. For example, hemo-cytes associated with epithelial tumors express the inflammatorycytokine Eiger/TNF. In the case of Ras-transformed, scribble mutanttumors, activation of TNF signaling has a tumor-promoting effect[209]. In contrast, in a different epithelial tumor model based on amutation in discs large (dlg) mutants, TNF signaling acts to suppresstumors [210].
Mounting an anti-tumor response by macrophages can dependon the concerted action of multiple molecular mechanisms. Inthe Drosophila dlg tumor model, hemocytes secrete not only TNFbut also Spätzle, the Toll pathway ligand. This results in a two-pronged tumor defense response: TNF signaling from hemocytespromotes tumor death directly, and Spätzle triggers a systemicimmune response in the fat body, which acts in parallel to inducetumor cell apoptosis [210].
There are also reports of synergy between bacterial infectionsand oncogenic mutations, which together promote more severegut dysplasia in response to tissue damage [214,215]. The Imd and
JNK signaling pathways mediate this interaction, but as of yet, norole for hemocytes has been demonstrated in the process. Thus, thecomplexities of the interactions between tumors, macrophages andcellular microenvironments are just beginning to be unraveled.
s in Im
4
tataDtigcdtbre
A
mfBbtDI0o
R
K.S. Gold, K. Brückner / Seminar
. Conclusions
Drosophila melanogaster has become a multifaceted and versa-ile model to dissect the mechanisms of macrophage developmentnd function. A large body of work has established high evolu-ionary conservation between this invertebrate and vertebrates,t the cellular and molecular level. Each developmental stage ofrosophila holds its own strengths for certain types of investiga-
ion, and in many cases their potential for experimental modelings expected to grow even further in the future. Drosophila and itsenetic toolkit allows us to investigate the mechanisms by whichellular microenvironments and long-range systemic signals coor-inate communication between various tissues, ultimately shapinghe development and adaptation of macrophages. It will furtherroaden our understanding of the innate cellular and humoralesponses in infection and tissue development, homeostasis, regen-ration and cancer.
cknowledgements
K.B. thanks F. Geissmann for advice on hematopoietic waves andacrophage lineages in vertebrate systems, and E. J. V. Ramond
or comments on the manuscript. We thank all members of therückner lab for discussion and feedback. This work was supportedy a postdoctoral fellowship from the American Heart Associa-ion (to K.S.G.), and grants from the American Cancer Society (RSGDC-122595), National Science Foundation (1326268), National
nstitutes of Health (1R01GM112083-01) and (1R56HL118726-1A1) (to K.B.). We apologize to authors whose work was not citedwing to oversight or space constraints.
eferences
[1] T. Rizki, R. Rizki, The cellular defense system of Drosophila melanogaster,Insect Ultrastruct. 2 (1984) 579–604.
[2] T.M. Rizki, The circulatory system and associated cells and tissues, in: M.Ashburner, T.R.F. Wright (Eds.), The Genetics and Biology of Drosophila, vol.2b, Academic Press, New York, 1978, pp. 397–452.
[3] U. Tepass, et al., Embryonic origin of hemocytes and their relationship to celldeath in Drosophila, Development 120 (7) (1994) 1829–1837.
[4] R. van Furth, M.M. Diesselhoff-den Dulk, Dual origin of mouse spleenmacrophages, J. Exp. Med. 160 (5) (1984) 1273–1283.
[5] P. Herbomel, B. Thisse, C. Thisse, Zebrafish early macrophages colonizecephalic mesenchyme and developing brain: retina, and epidermis througha M-CSF receptor-dependent invasive process, Dev. Biol. 238 (2) (2001)274–288.
[6] F. Ginhoux, et al., Fate mapping analysis reveals that adult microglia derivefrom primitive macrophages, Science 330 (6005) (2010) 841–845.
[7] C. Schulz, et al., A lineage of myeloid cells independent of Myb andhematopoietic stem cells, Science 336 (6077) (2012) 86–90.
[8] D. Hashimoto, et al., Tissue-resident macrophages self-maintain locallythroughout adult life with minimal contribution from circulatingmonocytes, Immunity 38 (4) (2013) 792–804.
[9] G. Hoeffel, et al., Adult Langerhans cells derive predominantly fromembryonic fetal liver monocytes with a minor contribution of yolksac-derived macrophages, J. Exp. Med. 6 (2012) 1167–1181.
[10] E. Gomez Perdiguero, et al., Tissue-resident macrophages originate fromyolk-sac-derived erythro-myeloid progenitors, Nature 518 (7540) (2015)547–551.
[11] G. Hoeffel, et al., C-Myb(+) erythro-myeloid progenitor-derived fetalmonocytes give rise to adult tissue-resident macrophages, Immunity 42 (4)(2015) 665–678.
[12] M. Haniffa, V. Bigley, M. Collin, Human mononuclear phagocyte systemreunited, Semin. Cell Dev. Biol. 41 (2015) 59–69.
[13] F.K. Swirski, I. Hilgendorf, C.S. Robbins, From proliferation to proliferation:monocyte lineage comes full circle, Semin. Immunopathol. 36 (2) (2014)137–148.
[14] E. Gomez Perdiguero, F. Geissmann, Myb-independent macrophages: afamily of cells that develops with their tissue of residence and is involved in
its homeostasis, Cold Spring Harb. Symp. Quant. Biol. 78 (2013) 91–100.
[17] K. Makhijani, et al., The peripheral nervous system supports blood cellhoming and survival in the Drosophila larva, Development 138 (2011)5379–5391.
[18] K. Makhijani, K. Brückner, Of blood cells and the nervous system:hematopoiesis in the Drosophila larva, Fly 6 (4) (2012) 254–260.
[19] K.S. Gold, K. Brückner, Drosophila as a model for the two myeloid blood cellsystems in vertebrates, Exp. Hematol. 42 (8) (2014) 717–727.
[20] N. Martinek, et al., Haemocyte-derived SPARC is required forcollagen-IV-dependent stability of basal laminae in Drosophila embryos, J.Cell Sci. 121 (Pt. 10) (2008) 1671–1680.
[21] T. Lebestky, et al., Specification of Drosophila hematopoietic lineage byconserved transcription factors, Science 288 (5463) (2000) 146–149.
[22] K.P. Rehorn, et al., A molecular aspect of hematopoiesis and endodermdevelopment common to vertebratesand Drosophila, Development 122 (12) (1996) 4023–4031.
[23] N. Fossett, et al., The Friend of GATA proteins U-shaped: fOG-1, and FOG-2function as negative regulators of blood, heart, and eye development inDrosophila, Proc. Natl. Acad. Sci. U. S. A. 98 (13) (2001) 7342–7347.
[24] R. Bernardoni, V. Vivancos, A. Giangrande, glide/gcm is expressed andrequired in the scavenger cell lineage, Dev. Biol. 191 (1) (1997) 118–130.
[25] C. Jacques, et al., A novel role of the glial fate determinant glial cells missingin hematopoiesis, Int. J. Dev. Biol. 53 (7) (2009) 1013–1022.
[26] T.B. Alfonso, B.W. Jones, gcm2 promotes glial cell differentiation and isrequired with glial cells missing for macrophage development in Drosophila,Dev. Biol. 248 (2) (2002) 369–383.
[27] N. Fossett, et al., Combinatorial interactions of serpent: lozenge, andU-shaped regulate crystal cell lineage commitment during Drosophilahematopoiesis, Proc. Natl. Acad. Sci. U. S. A. 100 (20) (2003) 11451–11456.
[28] N. Fossett, R.A. Schulz, Functional conservation of hematopoietic factors inDrosophila and vertebrates, Differentiation 69 (2-3) (2001) 83–90.
[29] C.J. Evans, V. Hartenstein, U. Banerjee, Thicker than blood: conservedmechanisms in Drosophila and vertebrate hematopoiesis, Dev. Cell 5 (5)(2003) 673–690.
[30] J.M. Frame, K.E. McGrath, J. Palis, Erythro-myeloid progenitors: definitivehematopoiesis in the conceptus prior to the emergence of hematopoieticstem cells, Blood Cells Mol. Dis. 51 (4) (2013) 220–225.
[31] K.E. McGrath, et al., Distinct sources of hematopoietic progenitors emergebefore HSCs and provide functional blood cells in the mammalian embryo,Cell Rep. 11 (12) (2015) 1892–1904.
[32] A. Zaidman-Remy, et al., The Drosophila larva as a tool to studygut-associated macrophages: pI3 K regulates a discrete hemocytepopulation at the proventriculus, Dev. Comp. Immunol. 36 (4) (2012)638–647.
[33] R. Sopko, et al., A systems-level interrogation identifies regulators ofDrosophila blood cell number and survival, PLoS Genet. 11 (3) (2015)e1005056.
[34] S. Petraki, B. Alexander, K. Bruckner, Assaying blood cell populations of theDrosophila melanogaster larva, J. Visualized Exp.: JoVE 105 (2015).
[35] A.B. Leitao, E. Sucena, Drosophila sessile hemocyte clusters are truehematopoietic tissues that regulate larval blood cell differentiation, LeitaoSucena Elife 4 (2015) e06166.
[36] A.J. Bretscher, et al., The Nimrod transmembrane receptor Eater is requiredfor hemocyte attachment to the sessile compartment in Drosophilamelanogaster, Biol. Open 4 (3) (2015) 355–363.
[37] R. Markus, et al., Sessile hemocytes as a hematopoietic compartment inDrosophila melanogaster, Proc. Natl. Acad. Sci. U. S. A. 106 (12) (2009)4805–4809.
[38] V. Van De Bor, et al., Companion blood cells control ovarian stem cell nichemicroenvironment and homeostasis, Cell Rep. 13 (3) (2015) 546–560.
[39] S.A. Sinenko, B. Mathey-Prevot, Increased expression of Drosophilatetraspanin, Tsp68C, suppresses the abnormal proliferation of ytr-deficientand Ras/Raf-activated hemocytes, Oncogene 23 (56) (2004) 9120–9128.
[40] B. Stramer, et al., Live imaging of wound inflammation in Drosophilaembryos reveals key roles for small GTPases during in vivo cell migration, J.Cell Biol. 168 (4) (2005) 567–573.
[41] E. Kurucz, et al., Definition of Drosophila hemocyte subsets by cell-typespecific antigens, Acta Biol. Hung. 58 (Suppl) (2007) 95–111.
[42] N.C. Franc, et al., Croquemort: a novel Drosophila hemocyte/macrophagereceptor that recognizes apoptotic cells, Immunity 4 (5) (1996) 431–443.
[43] T. Tokusumi, et al., New hemocyte-specific enhancer-reporter transgenes forthe analysis of hematopoiesis in Drosophila, Genesis 47 (11) (2009) 771–774.
[44] E. Kurucz, et al., Hemese: a hemocyte-specific transmembrane protein,affects the cellular immune response in Drosophila, Proc. Natl. Acad. Sci. U. S.A. 100 (5) (2003) 2622–2627.
[45] S.A. Sinenko, et al., Genetic manipulation of AML1-ETO-induced expansionof hematopoietic precursors in a Drosophila model, Blood 116 (22) (2010)4612–4620.
[46] P. Cognigni, A.P. Bailey, I. Miguel-Aliaga, Enteric neurons and systemicsignals couple nutritional and reproductive status with intestinalhomeostasis, Cell Metab. 13 (1) (2011) 92–104.
[47] N. Boulais, L. Misery, The epidermis: a sensory tissue, Eur. J. Dermatol.: EJD
18 (2) (2008) 119–127.
[48] L. Misery, Langerhans cells in the neuro-immuno-cutaneous system, J.Neuroimmunol. 89 (1–2) (1998) 83–87.
[49] K.E. Brack, The heart’s ‘little brain’ controlling cardiac function in the rabbit,Exp. Physiol. 100 (4) (2015) 348–353.
[50] D.H. Pauza, et al., Morphology: distribution, and variability of the epicardiacneural ganglionated subplexuses in the human heart, Anat. Rec. 259 (4)(2000) 353–382.
[51] N. Pauziene, et al., Innervation of the rabbit cardiac ventricles, J. Anat. 228(1) (2016) 26–46.
[52] R. Razavi, et al., TRPV1+ sensory neurons control beta cell stress and isletinflammation in autoimmune diabetes, Cell 127 (6) (2006) 1123–1135.
[53] H. Yang, et al., JAK/STAT signaling in Drosophila muscles controls the cellularimmune responseagainst parasitoid infection, EMBO Rep. 16 (12) (2015) 1664–1672.
[54] E. Gutierrez, et al., Specialized hepatocyte-like cells regulate Drosophila lipidmetabolism, Nature 445 (7125) (2007) 275–280.
[55] E. Dzierzak, N.A. Speck, Of lineage and legacy: the development ofmammalian hematopoietic stem cells, Nat. Immunol. 9 (2) (2008) 129–136.
[56] D. Gosselin, et al., Environment drives selection and function of enhancerscontrolling tissue-specific macrophage identities, Cell 159 (6) (2014)1327–1340.
[57] Y. Lavin, et al., Tissue-resident macrophage enhancer landscapes are shapedby the local microenvironment, Cell 159 (6) (2014) 1312–1326.
[58] T. Suzuki, et al., Pulmonary macrophage transplantation therapy, Nature 514(7523) (2014) 450–454.
[59] T. Lebestky, S.H. Jung, U. Banerjee, A serrate-expressing signaling centercontrols Drosophila hematopoiesis, Genes Dev. 17 (3) (2003) 348–353.
[60] S.H. Jung, et al., The Drosophila lymph gland as a developmental model ofhematopoiesis, Development 132 (11) (2005) 2521–2533.
[61] L. Mandal, U. Banerjee, V. Hartenstein, Evidence for a fruit fly hemangioblastand similarities between lymph-gland hematopoiesis in fruit fly andmammal aorta-gonadal-mesonephros mesoderm, Nat. Genet. 36 (9) (2004)1019–1023.
[62] J.P. Zape, A.C. Zovein, Hemogenic endothelium: origins, regulation, andimplications for vascular biology, Semin. Cell Dev. Biol. 22 (9) (2011)1036–1047.
[63] K.K. Hirschi, Hemogenic endothelium during development and beyond,Blood 119 (21) (2012) 4823–4827.
[64] J.A. Martinez-Agosto, et al., The hematopoietic stem cell and its niche: acomparative view, Genes Dev. 21 (23) (2007) 3044–3060.
[65] J. Krzemien, M. Crozatier, A. Vincent, Ontogeny of the Drosophila larvalhematopoietic organ, hemocyte homeostasis and the dedicated cellularimmune response to parasitism, Int. J. Dev. Biol. 54 (6–7) (2010) 1117–1125.
[66] L. Mandal, et al., A hedgehog- and antennapedia-dependent niche maintainsDrosophila haematopoietic precursors, Nature 446 (7133) (2007) 320–324.
[67] J. Krzemien, et al., Control of blood cell homeostasis in Drosophila larvae bythe posterior signalling centre, Nature 446 (7133) (2007) 325–328.
[68] S.A. Sinenko, et al., Dual role of wingless signaling in stem-likehematopoietic precursor maintenance in Drosophila, Dev. Cell 16 (5) (2009)756–763.
[69] M. Dragojlovic-Munther, J.A. Martinez-Agosto, Multifaceted roles of PTENand TSC orchestrate growth and differentiation of Drosophila bloodprogenitors, Development 139 (20) (2012) 3752–3763.
[70] J. Krzemien, et al., Hematopoietic progenitors and hemocyte lineages in theDrosophila lymph gland, Dev. Biol. 346 (2) (2010) 310–319.
[71] L.C. Davies, et al., Distinct bone marrow-derived and tissue-residentmacrophage lineages proliferate at key stages during inflammation, Nat.Commun. 4 (2013) 1886.
[72] C. Shi, E.G. Pamer, Monocyte recruitment during infection andinflammation, Nat. Rev. Immunol. 11 (11) (2011) 762–774.
[73] M. Grigorian, L. Mandal, V. Hartenstein, Hematopoiesis at the onset ofmetamorphosis: terminal differentiation and dissociation of the Drosophilalymph gland, Dev. Genes Evol. 221 (3) (2011) 121–131.
[74] M. Crozatier, et al., Cellular immune response to parasitization in Drosophilarequires the EBF orthologue collier, PLoS Biol. 2 (8) (2004) E196.
[75] D. Pennetier, et al., Size control of the Drosophila hematopoietic niche bybone morphogenetic protein signaling reveals parallels with mammals,Proc. Natl. Acad. Sci. U. S. A. 109 (9) (2012) 3389–3394.
[76] B. Benmimoun, et al., The EBF transcription factor Collier directly promotesDrosophila blood cell progenitor maintenance independently of the niche,Proc. Natl. Acad. Sci. U. S. A. 112 (29) (2015) 9052–9057.
[77] B.C. Mondal, et al., Interaction between differentiating cell- andniche-derived signals in hematopoietic progenitor maintenance, Cell 147 (7)(2011) 1589–1600.
[78] C.C. Milton, et al., The Hippo pathway regulates hematopoiesis in Drosophilamelanogaster, Curr. Biol.: CB 24 (22) (2014) 2673–2680.
[80] K.V. Myrick, C.R. Dearolf, Hyperactivation of the Hop jak kinase causes thepreferential overexpression of eIF1A transcripts in larval blood cells, Gene244 (1–2) (2000) 119–125.
[81] S. Minakhina, W. Tan, R. Steward, JAK/STAT and the GATA factor Panniercontrol hemocyte maturation and differentiation in Drosophila, Dev. Biol.352 (2) (2011) 308–316.
[82] P. Qiu, P.C. Pan, S. Govind, A role for the Drosophila Toll/Cactus pathway inlarval hematopoiesis, Development 125 (10) (1998) 1909–1920.
[83] M. Dragojlovic-Munther, J.A. Martinez-Agosto, Extracellularmatrix-modulated Heartless signaling in Drosophila blood progenitors
munology 27 (2015) 357–368
regulates their differentiation via a Ras/ETS/FOG pathway and target ofrapamycin function, Dev. Biol. 384 (2) (2013) 313–330.
[84] M. Grigorian, et al., The proteoglycan Trol controls the architecture of theextracellular matrix and balances proliferation and differentiation of bloodprogenitors in the Drosophila lymph gland, Dev. Biol. 384 (2) (2013)301–312.
[85] T. Tokusumi, et al., Germ line differentiation factor Bag of Marbles is aregulator of hematopoietic progenitor maintenance during Drosophilahematopoiesis, Development 138 (18) (2011) 3879–3884.
[86] T. Tokusumi, et al., Bag of Marbles controls the size and organization of theDrosophila hematopoietic niche through interactions with the Insulin-likegrowth factor pathway and Retinoblastoma-family protein, Development142 (13) (2015) 2261–2267.
[87] S. Minakhina, M. Druzhinina, R. Steward, Zfrp8: the Drosophila ortholog ofPDCD2, functions in lymph gland development and controls cellproliferation, Development 134 (13) (2007) 2387–2396.
[88] N. Remillieux-Leschelle, P. Santamaria, N.B. Randsholt, Regulation of larvalhematopoiesis in Drosophila melanogaster: a role for the multi sex combsgene, Genetics 162 (3) (2002) 1259–1274.
[89] A. Holz, et al., The two origins of hemocytes in Drosophila, Development 130(20) (2003) 4955–4962.
[90] C.J. Sampson, U. Amin, J.P. Couso, Activation of Drosophila hemocyte motilityby the ecdysone hormone, Biol. Open 2 (12) (2013) 1412–1420.
[91] A. Ayyaz, H. Li, H. Jasper, Haemocytes control stem cell activity in theDrosophila intestine, Nat. Cell Biol. 17 (6) (2015) 736–748.
[92] S. Ghosh, et al., Active hematopoietic hubs in Drosophila adults generatehemocytes and contribute to immune response, Dev. Cell 33 (4) (2015)478–488.
[93] A. Nelliot, N. Bond, D.K. Hoshizaki, Fat-body remodeling in Drosophilamelanogaster, Genesis 44 (8) (2006) 396–400.
[94] M. Elrod-Erickson, S. Mishra, D. Schneider, Interactions between the cellularand humoral immune responses in Drosophila, Curr. Biol.: CB 10 (13) (2000)781–784.
[95] M.S. Dionne, N. Ghori, D.S. Schneider, Drosophila melanogaster is agenetically tractable model host for Mycobacterium marinum, Infect. Immun.71 (6) (2003) 3540–3550.
[96] M.A. Akbar, et al., The full-of-bacteria gene is required for phagosomematuration during immune defense in Drosophila, J. Cell Biol. 192 (3) (2011)383–390.
[97] R. Lanot, et al., Postembryonic hematopoiesis in Drosophila, Dev. Biol. 230(2) (2001) 243–257.
[98] C.J. Evans, T. Liu, U. Banerjee, Drosophila hematopoiesis: markers andmethods for molecular genetic analysis, Methods 68 (1) (2014) 242–251.
[99] R.I. Clark, et al., Multiple TGF-beta superfamily signals modulate the adultDrosophila immune response, Curr. Biol.: CB 21 (19) (2011)1672–1677.
[100] L. Bataille, et al., Resolving embryonic blood cell fate choice in Drosophila:interplay of GCM and RUNX factors, Development 132 (20) (2005)4635–4644.
[101] D.K. Mackenzie, L.F. Bussiere, M.C. Tinsley, Senescence of the cellularimmune response in Drosophila melanogaster, Exp. Gerontol. 46 (11) (2011)853–859.
[102] L. Horn, J. Leips, M. Starz-Gaiano, Phagocytic ability declines with age inadult Drosophila hemocytes, Aging Cell 13 (4) (2014) 719–728.
[103] M.J. Williams, Drosophila hemopoiesis and cellular immunity, J. Immunol.178 (8) (2007) 4711–4716.
[104] L.M. Stuart, R.A. Ezekowitz, Phagocytosis and comparative innate immunity:learning on the fly, Nat. Rev. Immunol. 8 (2) (2008) 131–141.
[105] N.C. Franc, et al., Requirement for croquemort in phagocytosis of apoptoticcells in Drosophila, Science 284 (5422) (1999) 1991–1994.
[106] T.T. Tung, et al., Phosphatidylserine recognition and induction of apoptoticcell clearance by Drosophila engulfment receptor Draper, J. Biochem. 153 (5)(2013) 483–491.
[107] T. Kuraishi, et al., Pretaporter: a Drosophila protein serving as a ligand forDraper in the phagocytosis of apoptotic cells, EMBO J. 28 (24) (2009)3868–3878.
[108] C. Kocks, et al., Eater: a transmembrane protein mediating phagocytosis ofbacterial pathogens in Drosophila, Cell 123 (2) (2005) 335–346.
[109] E. Kurucz, et al., Nimrod: a putative phagocytosis receptor with EGF repeatsin Drosophila plasmatocytes, Curr. Biol.: CB 17 (7) (2007) 649–654.
[110] K. Somogyi, et al., Evolution of genes and repeats in the Nimrod superfamily,Mol. Biol. Evol. 25 (11) (2008) 2337–2347.
[111] K. Nagaosa, et al., Integrin betanu-mediated phagocytosis of apoptotic cellsin Drosophila embryos, J. Biol. Chem. 286 (29) (2011) 25770–25777.
[112] L. Zhou, et al., Programmed cell death in the Drosophila central nervoussystem midline, Curr. Biol. 5 (7) (1995) 784–790.
[113] H.C. Sears, C.J. Kennedy, P.A. Garrity, Macrophage-mediated corpseengulfment is required for normal Drosophila CNS morphogenesis,Development 130 (15) (2003) 3557–3565.
[114] M.J. Sonnenfeld, J.R. Jacobs, Macrophages and glia participate in the removalof apoptotic neurons from the Drosophila embryonic nervous system, J.
Comp. Neurol. 359 (4) (1995) 644–652.
[115] K. Brückner, et al., The PDGF/VEGF Receptor controls blood cell survival inDrosophila, Dev. Cell 7 (2004).
[116] M.M. Baer, et al., The role of apoptosis in shaping the tracheal system in theDrosophila embryo, Mech. Dev. 127 (1-2) (2010) 28–35.
117] S. Yasothornsrikul, et al., viking: identification and characterization of asecond type IV collagen in Drosophila, Gene 198 (1–2) (1997) 17–25.
118] C. Mirre, et al., De novo expression of a type IV collagen gene in Drosophilaembryos is restricted to mesodermal derivatives and occurs at germ bandshortening, Development 102 (2) (1988) 369–376.
119] M. Kusche-Gullberg, et al., Laminin A chain: expression during Drosophiladevelopment and genomic sequence, EMBO J. 11 (12) (1992) 4519–4527.
120] F.J. Fogerty, et al., Tiggrin: a novel Drosophila extracellular matrix proteinthat functions as a ligand for Drosophila alpha PS2 beta PS integrins,Development 120 (7) (1994) 1747–1758.
121] I.A. Kramerova, A.A. Kramerov, J.H. Fessler, Alternative splicing of papilinand the diversity of Drosophila extracellular matrix during embryonicmorphogenesis, Dev. Dyn. 226 (4) (2003) 634–642.
122] R.E. Nelson, et al., Peroxidasin: a novel enzyme-matrix protein of Drosophiladevelopment, EMBO J. 13 (15) (1994) 3438–3447.
123] G. Bhave, et al., Peroxidasin forms sulfilimine chemical bonds usinghypohalous acids in tissue genesis, Nat. Chem. Biol. 8 (9) (2012) 784–790.
124] K. Comber, et al., A dual role for the betaPS integrin myospheroid inmediating Drosophila embryonic macrophage migration, J. Cell Sci. 126 (Pt.15) (2013) 3475–3484.
125] B. Olofsson, D.T. Page, Condensation of the central nervous system inembryonic Drosophila is inhibited by blocking hemocyte migration or neuralactivity, Dev. Biol. 279 (1) (2005) 233–243.
126] S. Bunt, et al., Hemocyte-secreted type IV collagen enhances BMP signalingto guide renal tubule morphogenesis in Drosophila, Dev. Cell 19 (2) (2010)296–306.
127] D. Siekhaus, et al., RhoL controls invasion and Rap1 localization duringimmune cell transmigration in Drosophila, Nat. Cell Biol. 12 (6) (2010)605–610.
128] W. Wood, C. Faria, A. Jacinto, Distinct mechanisms regulate hemocytechemotaxis during development and wound healing in Drosophilamelanogaster, J. Cell Biol. 173 (3) (2006) 405–416.
129] A. Ratheesh, V. Belyaeva, D.E. Siekhaus, Drosophila immune cell migrationand adhesion during embryonic development and larval immune responses,Curr. Opin. Cell Biol. 36 (2015) 71–79.
136] I. Vlisidou, et al., Drosophila embryos as model systems for monitoringbacterial infection in real time, PLoS Pathog. 5 (7) (2009) e1000518.
137] K.L. Tan, I. Vlisidou, W. Wood, Ecdysone mediates the development ofimmunity in the Drosophila embryo, Curr. Biol.: CB 24 (10) (2014)1145–1152.
138] J. Shim, et al., Olfactory control of blood progenitor maintenance, Cell 155(5) (2013) 1141–1153.
139] J. Shim, T. Mukherjee, U. Banerjee, Direct sensing of systemic and nutritionalsignals by haematopoietic progenitors in Drosophila, Nat. Cell Biol. 14 (4)(2012) 394–400.
140] Y. Tokusumi, et al., Gene regulatory networks controlling hematopoieticprogenitor niche cell production and differentiation in the Drosophila lymphgland, PLoS One 7 (7) (2012) e41604.
141] B. Benmimoun, et al., Dual role for Insulin/TOR signaling in the control ofhematopoietic progenitor maintenance in Drosophila, Development 139 (10)(2012) 1713–1717.
142] S.A. Sinenko, J. Shim, U. Banerjee, Oxidative stress in the haematopoieticniche regulates the cellular immune response in Drosophila, EMBO Rep. 13(1) (2012) 83–89.
143] E. Owusu-Ansah, U. Banerjee, Reactive oxygen species prime Drosophilahaematopoietic progenitors for differentiation, Nature 461 (7263) (2009)537–541.
144] T.M. Rizki, R.M. Rizki, Lamellocyte differentiation in Drosophila larvaeparasitized by Leptopilina, Dev. Comp. Immunol. 16 (2–3) (1992) 103–110.
145] C. Small, et al., An introduction to parasitic wasps of Drosophila and theantiparasite immune response, J. Visualized Exp.: JoVE 2012 (63) (2016)pe3347.
146] R.P. Sorrentino, Y. Carton, S. Govind, Cellular immune response to parasiteinfection in the Drosophila lymph gland is developmentally regulated, Dev.Biol. 243 (1) (2002) 65–80.
147] H.J. Nam, et al., Involvement of pro-phenoloxidase 3 inlamellocyte-mediated spontaneous melanization in Drosophila, Mol. Cells 26
(6) (2008) 606–610.
148] L.M. Vanha-Aho, et al., Edin expression in the fat body is required in thedefense against parasitic wasps in Drosophila melanogaster, PLoS Pathog. 11(5) (2015) e1004895.
munology 27 (2015) 357–368 367
[149] M.R. Schmid, et al., Control of Drosophila blood cell activation via Tollsignaling in the fat body, PLoS One 9 (8) (2014) e102568.
[150] C.J. Zettervall, et al., A directed screen for genes involved in Drosophila bloodcell activation, Proc. Natl. Acad. Sci. U. S. A. 101 (39) (2004) 14192–14197.
[151] M.J. Williams, et al., Rac1 signalling in the Drosophila larval cellular immuneresponse, J. Cell Sci. 119 (Pt 10) (2006) 2015–2024.
[152] D. Ferrandon, J.L. Imler, J.A. Hoffmann, Sensing infection in Drosophila: tolland beyond, Semin. Immunol. 16 (1) (2004) 43–53.
[153] N.T. Nehme, et al., A model of bacterial intestinal infections in Drosophilamelanogaster, PLoS Pathog. 3 (11) (2007) e173.
[154] A. Basset, et al., The phytopathogenic bacteria Erwinia carotovora infectsDrosophila and activates an immune response, Proc. Natl. Acad. Sci. U. S. A.97 (7) (2000) 3376–3381.
[155] E. Foley, P.H. O’Farrell, Nitric oxide contributes to induction of innateimmune responses to gram-negative bacteria in Drosophila, Genes Dev. 17(1) (2003) 115–125.
[156] S.C. Wu, et al., Infection-induced intestinal oxidative stress triggersorgan-to-organ immunological communication in Drosophila, Cell HostMicrobe 11 (4) (2012) 410–417.
[157] C.A. Brennan, et al., Psidin is required in Drosophila blood cells for bothphagocytic degradation and immune activation of the fat body, Curr. Biol.:CB 17 (1) (2007) 67–72.
[158] I. Akhouayri, et al., Toll-8/Tollo negatively regulates antimicrobial responsein the Drosophila respiratory epithelium, PLoS Pathog. 7 (10) (2011)e1002319.
[159] B. Lemaitre, J. Hoffmann, The host defense of Drosophila melanogaster, Annu.Rev. Immunol. 25 (2007) 697–743.
[160] J.A. Hoffmann, J.M. Reichhart, Drosophila innate immunity: an evolutionaryperspective, Nat. Immunol. 3 (2) (2002) 121–126.
[161] C. Neyen, et al., Methods to study Drosophila immunity, Methods 68 (1)(2014) 116–128.
[162] A.K. Shia, et al., Toll-dependent antimicrobial responses in Drosophila larvalfat body require Spatzle secreted by haemocytes, J. Cell Sci. 122 (Pt. 24)(2009) 4505–4515.
[163] A.M. Pearson, et al., Identification of cytoskeletal regulatory proteinsrequired for efficient phagocytosis in Drosophila, Microbes Infect. 5 (10)(2003) 815–824.
[164] R. Markus, et al., Sterile wounding is a minimal and sufficient trigger for acellular immune response in Drosophila melanogaster, Immunol. Lett. 101 (1)(2005) 108–111.
[165] D.T. Babcock, et al., Circulating blood cells function as a surveillance systemfor damaged tissue in Drosophila larvae, Proc. Natl. Acad. Sci. U. S. A. 105 (29)(2008) 10017–10022.
[166] S.M. Cohen, in: M. Bate, A. Martinez Arias (Eds.), Imaginal disc developmentThe Development of Drosophila melanogaster, 2, Cold Spring HarborLaboratory Press, 1993, 2016, pp. 747–841.
[167] D.W. Williams, J.W. Truman, Cellular mechanisms of dendrite pruning inDrosophila: insights from in vivo time-lapse of remodeling dendriticarborizing sensory neurons, Development 132 (16) (2005) 3631–3642.
[168] C. Han, et al., Epidermal cells are the primary phagocytes in thefragmentation and clearance of degenerating dendrites in Drosophila,Neuron 81 (3) (2014) 544–560.
[169] J. Doherty, et al., Ensheathing glia function as phagocytes in the adultDrosophila brain, J. Neurosci. 29 (15) (2009) 4768–4781.
[170] J.A. Kiger Jr., J.E. Natzle, M.M. Green, Hemocytes are essential for wingmaturation in Drosophila melanogaster, Proc. Natl. Acad. Sci. U. S. A. 98 (18)(2001) 10190–10195.
[171] C.G. Moreira, A. Jacinto, S. Prag, Drosophila integrin adhesion complexes areessential for hemocyte migration in vivo, Biol. Open 2 (8) (2013) 795–801.
[172] M. Sander, et al., Drosophila pupal macrophages—a versatile tool forcombined ex vivo and in vivo imaging of actin dynamics at high resolution,Eur. J. Cell Biol. 92 (10–11) (2013) 349–354.
[173] J.C. Regan, et al., Steroid hormone signaling is essential to regulate innateimmune cells and fight bacterial infection in Drosophila, PLoS Pathog. 9 (10)(2013) e1003720.
[174] A. Defaye, et al., Genetic ablation of Drosophila phagocytes reveals theircontribution to both development and resistance to bacterial infection, J.Innate Immun. 1 (4) (2009) 322–334.
[175] B. Charroux, J. Royet, Elimination of plasmatocytes by targeted apoptosisreveals their role in multiple aspects of the Drosophila immune response,Proc. Natl. Acad. Sci. U. S. A. 106 (24) (2009) 9797–9802.
[176] B. Arefin, et al., Apoptosis in hemocytes induces a shift in effectormechanisms in the Drosophila immune system and leads to apro-inflammatory state, PLoS One 10 (8) (2015) e0136593.
[177] M. Ramet, et al., Functional genomic analysis of phagocytosis andidentification of a Drosophila receptor for E. coli, Nature 416 (6881) (2002)644–648.
[178] V.P. Losick, D.T. Fox, A.C. Spradling, Polyploidization and cell fusioncontribute to wound healing in the adult Drosophila epithelium, Curr. Biol.:CB 23 (22) (2013) 2224–2232.
[179] L. Soares, M. Parisi, N.M. Bonini, Axon injury and regeneration in the adult
Drosophila, Sci. Rep. 4 (2014) 6199.
[180] J.G. King, J.F. Hillyer, Infection-induced interaction between the mosquitocirculatory and immune systems, PLoS Pathog. 8 (11) (2012) e1003058.
[181] W.L. Nutting, A comparative anatomical study of the heart and accessorystructures of the orthopteroid insects, J. Morphol. 89 (1951) 501–598.
[182] J.C. Jones, in: A.S. Gordon (Ed.), Hemocytopoiesis in insects. Regulation ofHematopoiesis, Appleton, New York, 1970, pp. 7–65.
[183] V.B. Wigglesworth, Insect blood cells, Annu. Rev. Entomol. 4 (1959) 1–16.[184] H. Agaisse, et al., Signaling role of hemocytes in Drosophila
JAK/STAT-dependent response to septic injury, Dev. Cell 5 (3) (2003)441–450.
[185] P. Tzou, et al., Tissue-specific inducible expression of antimicrobial peptidegenes in Drosophila surface epithelia, Immunity 13 (5) (2000) 737–748.
[186] D. Ferrandon, et al., A drosomycin-GFP reporter transgene reveals a localimmune response in Drosophila that is not dependent on the Toll pathway,EMBO J. 17 (5) (1998) 1217–1227.
[187] Y. Apidianakis, L.G. Rahme, Drosophila melanogaster as a model host forstudying Pseudomonas aeruginosa infection, Nat. Protoc. 4 (9) (2009)1285–1294.
[188] L.N. Pham, A specific primed immune response in Drosophila is dependenton phagocytes, PLoS Pathog. 3 (3) (2007) e26.
[189] N.T. Nehme, et al., Relative roles of the cellular and humoral responses in theDrosophila host defense against three gram-positive bacterial infections,PLoS One 6 (3) (2011) e14743.
[190] A. Avet-Rochex, et al., Suppression of Drosophila cellular immunity bydirected expression of the ExoS toxin GAP domain of Pseudomonasaeruginosa, Cell. Microbiol. 7 (6) (2005) 799–810.
[191] E. Bergeret, et al., TM9SF4 is required for Drosophila cellular immunity viacell adhesion and phagocytosis, J. Cell Sci. 121 (Pt. 20) (2008)3325–3334.
[192] A. Braun, J.A. Hoffmann, M. Meister, Analysis of the Drosophila host defensein domino mutant larvae: which are devoid of hemocytes, Proc. Natl. Acad.Sci. U. S. A. 95 (24) (1998) 14337–14342.
[193] E.F. Stone, et al., The circadian clock protein timeless regulates phagocytosisof bacteria in Drosophila, PLoS Pathog. 8 (1) (2012) e1002445.
[194] F.L. Watson, et al., Extensive diversity of Ig-superfamily proteins in theimmune system of insects, Science 309 (5742) (2005) 1874–1878.
[195] C. Hauton, V.J. Smith, Adaptive immunity in invertebrates: a straw housewithout a mechanistic foundation, BioEssays 29 (11) (2007) 1138–1146.
[196] B. Chazaud, Macrophages: supportive cells for tissue repair andregeneration, Immunobiology 219 (3) (2014) 172–178.
[197] Y. Okabe, R. Medzhitov, Tissue biology perspective on macrophages, Nat.
Immuno. 17 (1) (2015) 9–17.
[198] X. Wang, et al., Increased infiltrated macrophages in benign prostatichyperplasia (BPH): role of stromal androgen receptor inmacrophage-induced prostate stromal cell proliferation, J. Biol. Chem. 287(22) (2012) 18376–18385.
munology 27 (2015) 357–368
[199] T. Kamo, H. Akazawa, I. Komuro, Cardiac nonmyocytes in the hub of cardiachypertrophy, Circ. Res. 117 (1) (2015) 89–98.
[200] E.M. Kelsey, et al., Schnurri regulates hemocyte function to promote tissuerecovery after DNA damage, J. Cell Sci. 125 (Pt. 6) (2012) 1393–1400.
[201] E.F. Fogarty, et al., Extracellular reactive oxygen species driveapoptosis-Induced proliferation via drosophila macrophages, Curr. Biol.(2016) 26, http://dx.doi.org/10.1016/j.cub.2015.12.064.
[202] N. Buchon, et al., Invasive and indigenous microbiota impact intestinal stemcell activity through multiple pathways in Drosophila, Genes Dev. 23 (19)(2009) 2333–2344.
[203] B. Biteau, et al., Lifespan extension by preserving proliferative homeostasisin Drosophila, PLoS Genet. 6 (10) (2010) e1001159.
[204] A. Ayyaz, H. Jasper, Intestinal inflammation and stem cell homeostasis inaging Drosophila melanogaster, Front. Cell. Infect. Microbiol. 3 (2013) 98.
[205] T. Christofi, Y. Apidianakis, Drosophila and the hallmarks of cancer, Adv.Biochem. Eng./Biotechnol. 135 (2013) 79–110.
[206] M. Tipping, N. Perrimon, Drosophila as a model for context-dependenttumorigenesis, J. Cell. Physiol. 229 (1) (2014) 27–33.
[207] T. Hauling, et al., A Drosophila immune response against Ras-inducedovergrowth, Biol. Open 3 (4) (2014) 250–260.
[208] J.C. Pastor-Pareja, M. Wu, T. Xu, An innate immune response of blood cells totumors and tissue damage in Drosophila, Dis. Models Mech. 1 (2–3) (2008)144–154, discussion 153.
[209] J.B. Cordero, et al., Oncogenic Ras diverts a host TNF tumor suppressoractivity into tumor promoter, Dev. Cell 18 (6) (2010) 999–1011.
[210] F. Parisi, et al., Transformed epithelia trigger non-tissue-autonomous tumorsuppressor response by adipocytes via activation of Toll and Eiger/TNFsignaling, Cell Rep. 6 (5) (2014) 855–867.
[211] K.S. Siveen, G. Kuttan, Role of macrophages in tumour progression,Immunol. Lett. 123 (2) (2009) 97–102.
[212] A. Mantovani, et al., Cancer-related inflammation, Nature 454 (7203) (2008)436–444.
[213] A. Sica, P. Allavena, A. Mantovani, Cancer related inflammation: themacrophage connection, Cancer Lett. 267 (2) (2008) 204–215.
[214] Y. Apidianakis, et al., Synergy between bacterial infection and geneticpredisposition in intestinal dysplasia, Proc. Natl. Acad. Sci. U. S. A. 106 (49)
[215] E. Bangi, et al., Immune response to bacteria induces dissemination ofRas-activated Drosophila hindgut cells, EMBO Rep. 13 (6) (2012) 569–576.
[216] J. Oyallon, et al., Two independent functions of collier/early B cell factor inthe control of drosophila blood cell homeostasis, PLoS One (2016) e0148978.
![ScienceDirect cienceirect ScienceDirect · and. {[,], , , : . , / ...](https://static.documents.pub/doc/80x56/608077a6d3af4a2358487f59/-sciencedirect-cienceirect-sciencedirect-and-.jpg)
