180 Morphology and development of blood and immunity cell

(Blood and hemopoiesis)

Lecture 2013

Bloodstructure and function

• „connective tissue“ (cells and ECM ) blood cells and plasma

• erythrocytes (red blood cells)• leukocytes (white blood cells)• platelets• serum – differs from plasma by the

absence of factors (oraganic and anorganic), which leave plasma during coagulation (has been involved in clot)

• hematocrit - the volume of combined formed elements in the blood after centrifugation

• erythrocytes – 43%• leukocytes and platelets (buffy coat) 1%• 40-50% male• 30-40% female

Blood structure and function

• total volume 5,5L• transport : oxygen, CO2, nutrients, waste products,

hormones…• maintaining of acid/base and osmotic balance, body

temperature• plasma: water, proteins (albumin, globulins, clotting

proteins, complement, lipoproteins), inorganic salts, ions, nitrogenous compounds, nutrients, gases

• the interstitial fluid of connective tissues is derived from blood plasma

Formed elementstransport O2 , protection, clotting

Erythrocytes I.red blood cells

biconcave-shaped discs without nucleus and typical organells shape provides the cell with larger surface area (140 m2

an important attribute in gas exchange size: 7,5 x 2,6 μm (in the middle only 0,8 μm) number: 3,9 – 5,5 milions in 1μL (geographical difference -

particular reference values) they survive 120 days in circulation

7,2um

Erythrocytes II.• the shape of RBC is maintained by membrane proteins integral

membrane proteins: glycophorins glycosylated – express specific blood groups + bind to the cytoskeleton , band3 protein – binds hemoglobin

• peripheral membrane proteins arranged into two-dimensional hexagonal lattice network (spectrin, actin tetramers).. purpose: elasticity and stability – to be able to mechanical deformities, osmotic pressure..

• hemoglobin (33%), HbA, HbA2, HbF - fetal – particular types acc. to the polypeptide chain (! myoglobin – oxygen- binding protein in striated muscle)

• enzymes:- anaerobic glycolysis, hexose- monophosphate shunt

Clinical applications

anemia – decrease in the concentration of Hb polycythemia – physiological adaptation or haemoblastosis – it

increases blood viscosity anisocytosis – higher variability in size macrocytes – greater – impairment of maturation (deficiency of vit.

B12) microcytes – smaller (defeiciency of iron) defects in cytoskeleton: hereditary spherocytosis – primary defect in

spectrin gene expression sicle cell disease/thallasemia – point mutation in the gene for

hemoglobin – HBS shape – abnormal/crescent shape of RBC (red blood cell) clinically manifested as anemia, small vessels/venules obstruction, hemolysis

Leukocytes – white blood cells types acc. to presence and absence of the granules

• granulocytes• neutrophils (polymorphonuclear

leucocytes)• eosinophils• basophils• agranulocytes/mononuclear – see mononuclear

phagocyte system• lymphocytes , B, T• monocytes

neutrophil eosinophil

basophill lymphocyte

monocytes

Leukocytes

• circulate in blood stream, use it for their transport to connective tissue (by diapedesis), where they perform their function

• an important property of WBC is their motility

• non-specific immune response

Granulocytes

content of two granule types: specific with specific function for particular granulocyte

type nonspecific/azurophilic (lysosomes)

nuclei are divided in two or more lobes /segments all granulocytes in periferal blood are terminal postmitotic

stages of the cell development – cells do not divide. They survive only few days in peripheral blood

nuclei are divided in two or more lobes

Neutrophilthe most common WBC

Neutrophilic granulocytes 60-70% of leucocytes size: 12-15 μm (in smear) nucleus is divides in two or three lobes that are connected by chromatin bridges; (small appendage to the nucleus inactive second X chromosome – Barr body in females´neutrophils

good indentified) 2 types granules: specific granules – small, near the limit of resolution in LM (collagenase,

phospholipidase, complement activators. Phosphatase, metalloproteinases - migration)

azurophilic granules/lysosomes – 0,5 μm (myeloperoxidase – generates highly reactive bactericidal hypochlorite and chloramines)

glycogen – source of energy – anaerobic metabolism phagocytosis, oxidative burst – (H2O2) and oxygen radicals, enzymatic

degradation

Neutrophil – „microphage”the first line cells that enter the area of tissue damage

• chemoattraction to sites of microorganism invasion

• phagocytosis of microorganisms (with/without previous opsonisation– coating by antibody - Ab/complement to make bacteria more attractive)

• antigen-Ag engulfment,internalization - phagosome

• digestion - release of hydrolytic enzymes and by reactive oxidative compounds in phagosome (superoxide, hydrogen peroxide, hypochlorous acid (oxidative stress)

• only once perform a phagocytosis and die (pus)

• production of IL-1 – pyrogen(fever-inducing agent) – induces Pg synthesis – termoregulatory centre in hypothalamus - fever

Eosinophilic granulocytesassociated with allergic reaction, parasitic infections and chronic

inflammation 2-4% of WBC size: 12-15 μm bilobed nucleus specific granules: crystalline core

(internum) – major basic protein and other proteins with cytotoxic activity

arylsulfatase, histaminase, collagenase, cathepsin

matrix (externum) - lighter• azurophilic granules – lysosomes• thanks to histaminase moderates

deleterious effect of vasoactive substances

• Ag/AB phagocytosis• antihelmintic host defense• chronic inflammation - present in

lamina propria

Basophilic granulocytesacts like mast cell

less that 1% size 12-15 μm nucleus is divided in irregular lobes,

but it is not distinct because it is covered by granules (basophilic nucleus/ basophilic granules – heparan-sulfate)

specific granules – metachromatic, content of heparan-sulfate, histamine and SRS-A

after binding of Ag specific for IgE (binded on the surface through Fc receptors) the release of vasoactive agent is triggered – severe vascular disturbances – hypersensitivity and anafylaxis

Lymphocytesthe main functional cell of the immune system

in the blood they are represent the circulating immunocompetent cells, in transit from one lyphatic tissue to other

30% of WBC on the basis of size: small (6-8μm), medium-sized

and large (up to 30μm) – activated lymphocytes or NK

small lymphocytes prevail in blood – memory cells

dark, large round nucleus, chromatin is condensed

thin rim of cytoplasm, ribosomes, azurophilic granules

Lymphocytes types T cells , B cells, NK3

functionally distinct BUT morphologically identical

T lymphocytes cell-mediated

immunity differentiate in thymus,

prevail in peripheral blood: 65% - 75%

specific immunity T lymphocytes subtypes cytotoxic CD8+,

recognise Ag bound to MHC I (induce apoptosis)

supressor CD8+, CD45+ helper CD4+ recognise

Ag bound to MHC II

B lymphocytes humoral immunity,

Ab CD 19+ (B-cell

differentiates in plasma cell producing antibody)

20-30% in blood differentiate in bursa

Fabricii in birds and bursa equivalent (e.g. bone marrow) in mammals

NK (natural killers) CD16+, CD56+, CD94+ medium-sized

lymphocytes with granules

10-15% in peripheral blood – nonspecific recognition of tumor and virus infected cells - innate immune response

a bit morphological difference – larger and with granules

Monocytesmononuclear-phagocytic system

size: 12 -20μm oval, horseshoe or kidney

shaped nucleus, excentrically placed

basophilic cytoplasm, azurophilic granules (lysosomes), RER, polyribosomes, mitochondria, Golgi complex

monocytes differentiate into macrophages

phagocytosis repeatadly antigen presenting cells (express Ag in complex with

MHC II)

Leukocytes - differential white cell count: the distribution of the different types of white cells present in circulating blood

6 000 -10 000 in 1μL granulocytes neutrophiles 60 -70%, 3500-7500 eosinophiles 2-4%, 150 - 400 basophiles 0-1% 50-100

agranulocytes lymphocytes 20-30% 1500-2500 monocytes 3-8% 200-800

Platelets - thrombocytes nonnucleated, disc-like cell fragments of megakaryocytes size - 2-4 μm 200 000– 400 000 in uL glycocalyx – reaction surface for fibrin from fibrinogen formation central zone containing granules – granulomera: granules platelet-

specific proteins: fibrinogen, PdGF, FGF, von Willebrandt factor, platelet-specific factor IV ,δ granules dense bodies – ATP and serotonin; λ – lysosomes, mitochondria, peroxisomes, glycogen

and peripheral lighter zone – hyalomera - open canalicular system –membrane channels – develiopmental remnant, dense tubular system – RER – Ca2+ storage, marginal bundle of microtubules, actin and myosin – contractile

hemophilia – inherited deficiency of factor VIII or IX von Willebrand disease – the most frequent bleeding disorder, hereditary disease with

abnormal or defect of von Willebrand factor

Plateletsblood clot formation, surveillance of endotehel continuity,

repair of injured tissue

Hemopoeisis

Chick embryo – blood islands, 2ED

• mesoderm of yolk sac •(3 week)• intraembryonic splanchnic mesoderm (3week – 6week)• liver• spleen (hepato-lineal period)•bone marrow (from8week)

Development of blood cells regulation

microenvironment – cells of stroma, extracellular matrix

growth factors: growth factors –

stimulation of mitotic activity

colony-stimulating factors (CSF)

hematopoietins (erythropoietin – synthesis in kidney, thrombopoeitin - synthesis in liver)

Red bone marrow

stroma: hematopoietic cords and sinusoids stroma – reticular connective tissue (reticular cells and

reticular fibres – (collagen type 1 and 3, fibronectin, laminin and proteoglycans)

sinusoids – capillaries with discontinuous endothelium stem cells – they can differentiate also in other cellular

types that blood cells – appropriate stimulation is necessary

Hemopoeisis hemopoiesis is a result of simultaneous proliferation and

differentiation hemopoetic stem cells – types and terms:pluripotent stem cell – self-renewal - for life-long reserve – low

mitotic activitymultipotent - progenitor - stem cell - lymphoid and myeloid stem

cells unipotent - - colony forming cells (CFU - self-renewing – high

mitotic activityprecursor cells (blasts) – not self-renewing (lymphoblast,

erythroblast....)mature cells – (cytes) (lymphocyte, erythrocyte)

Hematopoiesis

Haemopoiesis

Erythropoiesis

erythropoietin, iron, folic acid, cyancobalamin (vit B12) 3 - 5 division from proerythroblast to erythrocyte approximately 7 days from proerythroblast to reticulocyte decrease of the cell volume condensation of chromatin (pycnotic nucleus) and its

expulsion synthesis of hemoglobin and successive loss of basophilia

(polyribosomes)

Erythroblastic islandnon-mature red blood cells with still present nucleus , dense

chromatin

Erythropoiesis

Proerythroblast – large cell with loose chromatin, nucleoli and basophilic cytoplasm

Basophilic erythroblast – condensed nucleus, basophilic cytoplasm - polyribosomes

Polychromatophilic erythroblast – polyribosomes decrease, hemoglobin appears

Orthochromatophilic erythroblast – eosinophilic cytoplasm- hemoglobin, maximally condensed nucleus – nucleus expulsion

Reticulocyte – rest of ribosomes – substantia reticulo-filamentosa – 1% in peripheral blood

Erythrocyte

Granulopoiesis

in bone marrow more frequent than RBC (short life-time) gradual synthesis of azurophilic and later also specific

granules myeloblast – finely dispersed chromatin, no granules promyelocyte – the 2nd largest , basophilic cytoplasm,

Golgi complex and azurophilic granules neutrophilic, basophilic and eosinophilic myelocytes –

condensation of nucleus, appearance of specific granules neutrophilic metamyelocyte, post-mitotic – band cell – mature granulocyte

Bone marrow: promyelocyte , metamyelocyte, lymphocyte

Excentrical, nucleus, flat from one side

metamyelocyte

lymphocyte

Maturation of lymphocytes

no specific morphologic differences stem cells - progenitors in bone marrow –– they do not

have antigens specific for B and T lymphocytes T – lymphocytes - maturation in thymus (precursors T-

lymphoblasts – differentiate in mature lymphocytes) or in bone marrow (B – lymphoblasts, lymphocytes), they may divide in periphery in lymphoid organs (spleen, lymph node, tonsil)

Maturation of monocytes monoblast – identical with myeloblast promonocyte – large cell – up to 18μm; basophilic

cytoplasm, large slightly indented nucleus, large amount of RER, large Golgi complex

formation of azurophilic granules – lysosomes in blood, they circulate approximately 8 hours they survive in periphery for several months –

macrophages - antigen presenting cells

Origin of platelets megakaryoblast – 15 - 50 μm, large ovoid nucleus,

numerous nucleoli. Polyploid cell - up to 30 sets of chromosomes (reflecting its size)

megakaryocyte – giant cell - 35 – 150 μm. irregular nucleus, numerous mitochondria, well-

developed RER and extensive Golgi complex. Formation of granules. Invagination of plasmalemma – demarcation membranes – fragmentation of cytoplasm – release of platelets into the blood

after desintegration of cytoplasm into the platelets, megakaryocyte die by apoptosis