Normal Hemopoiesis

Ahmad Sh. SilmiMsc Haematology, FIBMS

Lifespan and production of blood cells

Cell typeApproximate

lifespan

Production rate

cells/day

Production rate

cells/sec

Production rate

Kg/year

Red Cells100 days2 x 10112.3

million7.3

Neutrophilst½ 6 hours3 x 1010350,00010.9

Platelets7 days1 x 10111.2

million4.6

Lymphocytes

t½ 10 days1 x 1010116,0003.7

Annual total

26.5 Kg

So our body is in a continuous dynamic and a very rapid cell

turnover to be able to live.

HOW ?

It’s the Stem Cell !

HEMOPOIESIS: INTRO

Hemo: Referring to blood cellsPoiesis: “The development or production

of”The word Hemopoiesis refers to the

production & development of all the blood cells: Erythrocytes: Erythropoiesis Leucocytes: Leucopoiesis Thrombocytes: Thrombopoiesis.

HEMOPOIESIS Hemopoiesis depends on 3 important

components: the bone marrow stroma (Local

control) the hemopoietic stem and progenitor

cells the hemopoietic growth factors

(Humoral control)

STEM CELL THEORYSTEM CELL THEORY

The dazzling array of all the blood cells are The dazzling array of all the blood cells are produced by theproduced by the bone marrowbone marrow..

They all come from a single class of primitive They all come from a single class of primitive mother cells called as: mother cells called as:

PLURIPOTENT STEM CELLSPLURIPOTENT STEM CELLS..

These cells give rise to blood cells of:These cells give rise to blood cells of: Myeloid Myeloid series: Cells arising mainly from the series: Cells arising mainly from the

bone marrow.bone marrow. LymphoidLymphoid series: cells arising from lymphoid series: cells arising from lymphoid

tissues.tissues.

STEM CELLSSTEM CELLSThese cells have extensive proliferative These cells have extensive proliferative

capacity and also the:capacity and also the: Ability to give rise to new stem cellsAbility to give rise to new stem cells ((Self Self

RenewalRenewal)) Ability to differentiate into any blood cells linesAbility to differentiate into any blood cells lines

((PluripotencyPluripotency))

They grow and develop in the bone marrow.They grow and develop in the bone marrow.

The bone marrow & spleen form a supporting The bone marrow & spleen form a supporting system, called the system, called the

““hemopoietic microenvironment”hemopoietic microenvironment”

STEM CELLS: TypesSTEM CELLS: Types

Pluripotent Stem cellsPluripotent Stem cells:: Has a diameter of 18 – 23 Has a diameter of 18 – 23 μμ.. Giving rise to: both Myeloid and Lymphoid series of Giving rise to: both Myeloid and Lymphoid series of

cellscells Capable of extensive self-renewal.Capable of extensive self-renewal.

Myeloid Stem cellsMyeloid Stem cells: Generate myeloid cells:: Generate myeloid cells: ErythrocytesErythrocytes Granulocytes: PMNs, Eosinophils & Basophils.Granulocytes: PMNs, Eosinophils & Basophils. Thrombocytes.Thrombocytes.

Lymphoid Stem cellsLymphoid Stem cells: Giving rise only to:: Giving rise only to: Lymphocytes: T type mainly.Lymphocytes: T type mainly.

Routes a stem cell can takeself-renew

differentiate

Self renewal of stem cells

Symmetric cell division Asymmetric cell division

Stem cells divide asymmetrically Non-stem cells divide symmetrically

Rules of Normal Cell Proliferation

1

3

2

Stem cells self renew--immortal non-stem cells have finite life span

But also when it is required : Stem cells divide symmetrically to restore stem cell quantity

Stem cells symmetric cell division

CLONAL HEMOPOIESISCLONAL HEMOPOIESIS

STEM CELL

MULTIPLICATION COMMITTMENT

COMMITTEDSTEM CELL

COMMITTEDSTEM CELL

MULTIPLICATION

CFU: COLONYFORMING UNIT

CLONAL HEMOPOIESIS: CLONAL HEMOPOIESIS: (Contd)(Contd)COLONY FORMING UNIT

(CFU)

INTERMEDIATEBLAST CELLS

MATURE BLOOD CELLSEND CELLS: FINITE LIFE SPAN

MORPHOLOGICALLY RECOGNIZABLE

Properties of stem cells

1. Self renewal

2. Hierarchy 

3. Extensive proliferative capacity 

4. Cell cycle status 

5. Surface Markers 

6. Interact with microenvironment 

Stem Cell Hierarchy

Stem Cell Progression Is Associated By Changes In:

- Specific cell markers- Receptors - Adhesion molecules - Chromatin openness- Access to epigenetic transcription factors and loss of proliferative potential.

SITES OF HEMOPOIESISYolk sacYolk sac

Liver and spleenLiver and spleen

Bone marrowBone marrow–Gradual replacement Gradual replacement of active (red) of active (red) marrow by inactive marrow by inactive (fatty) tissue(fatty) tissue–Expansion can occur Expansion can occur during increased during increased need for cell need for cell productionproduction

SITES OF HEMOPOIESIS

Active Hemopoietic marrow is found, in children throughout the: Axial skeleton:

Cranium Ribs. Sternum Vertebrae Pelvis

Appendicular skeleton:

• Bones of the Upper & Lower limbs

In Adults active hemopoietic marrow is found only in:

•The axial skeleton•The proximal ends of the appendicular skeleton.

Sites of HemopoiesisHemopoiesis starts as early as yolk sac development.

2-3 weeks after fertilization 3 layers are developed (ecto, meso, and endoderm)

Hemoangioblast which is derived from the mesoderm

Hemoangioblast

Endothelial stem cell

Will develop to Blood vessels

Hemopoietic stem cell

will develop to Blood cells

In the embryo 2 week old embryo, hematopoiesis

begins in yolk sac. THE 1ST CELL TO BE PRODUCED IS

erythrocytes By 2 month old fetus, granulocyte

and megakaryocyte production. 4th month, lymphocytes

production. 5th month, monocytes produced.

CONTINUED..…

In the 3rd to 7th month of fetal life Hemopoietic stem cells will migrate to the liver and spleen, where hemopoiesis starts there and hemopoiesis is still mainly erythropoietic in nature, with minimal granulopoiesis

The bone marrow (BM)The stem cells then migrate to the bone

marrow (BM) where hemopoiesis starts and continue all over the life. In the bone marrow all types of blood cells are formed which include:

RBCSGranulocytes: Neutrophils, Eosinophils,

BasophilsLymphocytesMonocytes and macrophagesPlatelets

Extramedullary Hemopoiesis

When required, yellow marrow can be replaced by red marrow.

Liver & spleen can aslo resumed.This will multiply the production by 6.

Remark that Hemopoiesis within the marrow is called intramedullary or medullary hemopoiesis

Stages in haemopoietic cell development

Cell hierarchy (Haemopoiesis Cell hierarchy (Haemopoiesis schematic representation)schematic representation)

Hematopoietic Inductive Microenvironment

Why hemopoietic cells reside in the bone marrow

The stromal matrix plays an important role in presenting

growth factors and nutrients to developing blood cells.

The  most immature cells have receptors which bind them to proteoglycan molecules on the matrix and to receptors on the stromal cells (i.e. macrophages, fibroblasts, fat cells and endothelial cells)

There are lineage specific regions ( "niches" ) which provide  the molecular basis  for homing of transplanted stem cells.

The unique supportive microenvironment stem cell niche       - regulates proliferation and differentiation      - supports survival and inhibits apoptosisSimilar principles apply to malignant stem cells in myeloid leukemias

The sinusoids are lined with specialized endothelial cells which play an important role by producing factors which regulate growth and differentiation.

Interaction of stromal cells, Interaction of stromal cells, growth factors and haemopoietic growth factors and haemopoietic

cellscells

Stromal Cells of BM

Endothelial cellsFat cellsFibroblastsLymphocytesMacrophage

Haemopoietic growth Haemopoietic growth factorsfactors

Haemopoietic growth Haemopoietic growth factorsfactors

The haemopoeitic growth factors are glycoprotein hormones that regulate the proliferation and differentiation of haemopoietic progenitor cells and the function of mature blood cells.

T lymphocytes, monocytes, marcrophages and stromal cells are the major sources of growth factors except for erythropoietin, 90% of which is synthesized in the kidney and thrombopoietin, made largely in liver.

Haemopoietic growth factors Haemopoietic growth factors OverviewOverview

Regulate growth and differentiation -  a family of glycoproteins with

clinical utility-  with different specificities-  with different origins-  bind to cognate receptors on progenitor cells-  act locally or at a distance-  regulate proliferation and differentiation-  prevent apoptosis-  enhance function of some end stage cells      eg. GM-CSF enhances PMN function....,

Adhesion molecules /integrins

Haemopoietic growth factorsHaemopoietic growth factors

GM-CSFGM-CSF Granulocyte-Macrophage colony stimulating Granulocyte-Macrophage colony stimulating

factorfactor

M-CSFM-CSF Macrophage colony stimulating factorMacrophage colony stimulating factor

ErythropoietinErythropoietin Erythropoiesis stimulating hormoneErythropoiesis stimulating hormone

(These factors have the capacity to stimulate the (These factors have the capacity to stimulate the proliferation of their target progenitor cells when used proliferation of their target progenitor cells when used as a sole source of stimulation)as a sole source of stimulation)

ThrombopoietinThrombopoietin Stimulates megakaryopoiesisStimulates megakaryopoiesis

Haemopoietic growth factorsHaemopoietic growth factors

CytokinesCytokines IL 1 (Interleukin 1)IL 1 (Interleukin 1) IL 3IL 3 IL 4IL 4 IL 5IL 5 IL 6IL 6 IL 9IL 9 IL 11IL 11 TGF-TGF-ββ SCF (Stem cell factor, also known as kit-ligand)SCF (Stem cell factor, also known as kit-ligand)

Cytokines have no (e.g IL-1) or little (SCF) capacity to stimulate Cytokines have no (e.g IL-1) or little (SCF) capacity to stimulate cell proliferation on their own, but are able to synergise with cell proliferation on their own, but are able to synergise with other cytokines to recruit nine cells into proliferationother cytokines to recruit nine cells into proliferation

Role of growth factors in Role of growth factors in normal haemopoiesisnormal haemopoiesis

Order of blood cell formation1:STEM CELLS

2 :Progenitor cells may be mutli-potential, bi-potential or uni-potential

3 :Precursor cells, or also called maturing cells

4 :Terminally differentiated cells Mature cells

Precursor cells

Precursor cells

Precursor cells

Precursor cells

Stem Cells Stem Cells: undifferentiated cells that give rise

to all of the bone marrow cells. Only 0.5% of all marrow nucleated cells. Multipotential precursors. High self-renewal – give rise to daughter stem

cells that are exact replicas of the parent cell. Not morphologically distinguishable At any

time, the majority of stem cells (95%) are out of the cell cycle (they are in G0 mode/phase, also called quiescent).

The current phenotype is: CD34+CD38-Lin-HLA-DR-Rh123Dull

Progenitor cells of the BM Stem cells which undergo differentiation. Limited self-renewal ability. Multipotential but Gradually they

become unilineage or committed progenitor cell.

~3% of total nucleated hematopoietic cells of bone marrow

Progenitor cells of the BM Form colonies of cells in semisolid media in

vitro – described as colony forming units (CFU).

CFU-GEMM (granulocytic, erythrocytic, monocytic,megakaryocytic,CFU-GM,CFU-Mk, etc. )

Survival and differentiation of progenitor cells

influenced by growth regulatory glycoproteins, called cytokines – include interleukins, colony stimulating factors

Stem cells & progenitor cells are not recognized morphologically but all look like small mononuclear lymphocytes

Morphology of stem cells and progenitor cells

Maturing blood cells 1- Majority of cells (>95%)

2- lose adherence receptors,  become deformable.

3- migrate through cytoplasm of  lining

endothelial cell to enter  sinusoids. 4. Platelets are the exception. Megakaryocytes

  form  part of the sinusoidal wall.  They form long processes of proplatelets which fragment into nascent platelets.

Regulation of Regulation of HaemopoiesisHaemopoiesis

There should be a balance between cell production and cell death except at There should be a balance between cell production and cell death except at the times of requirementthe times of requirement

Regulation of HaemopoiesisLocal environmental control

Stromal cell mediated Haemopoiesis

Haemopoietic growth factors (Humoral regulation)

Apoptosis

Regulation of Regulation of HaemopoiesisHaemopoiesis

Immunoglobulin superfamily - Growth Factor Receptors (GFr) bind to cognate "ligand" to initiate signal transduction

( GF binds to extracellular domain of GFr, alters configuration of cytoplasmic domain,  causes phosphorylation of a tyrosine kinase and  initiates the signal that is ultimately transmitted to the nucleus.)

Selectins are involved in:

a) inflammatory and immune responses                                   b) platelet adhesion and activation

Integrins - control traffic and specific cell functions                - adhere to matrix niches                - release from marrow                -  homing of lymphocytes and stem cells etc.

Apoptosis important for homeostasis

Hematopoietic cells are programmed to self destruct but can be rescued from apoptosis by:

 specific growth factors certain gene products specific antigen some viruses eg EBV

Mechanism of apoptosis

Apoptosis, Continue

Defects in the apoptotic pathway are very important in causing diseases such as  chronic lymphocytic leukemia (CLL), and in enhancing resistance to chemotherapy in malignancy.

Induction of apoptosis  is a therapeutic strategy in resistant CLL

Inappropriate apoptosis  is a disease mechanism in myelodysplasyic syndromes.

Apoptosis is induced by chemotherapy, and resistance to chemotherapy is associated with blocked apoptosis.

Assessment of hemopoiesis

Hemopoiesis can be assessed clinically by;

1- (FBC, CBC= complete blood count) on peripheral blood.

2- Bone marrow Aspiration also allows assessment of the later stages of maturation of hemopoietic cells.

3- Bone marrow Trephine Biopsy provides a core of bone and bone marrow to show architecture.

Bone marrow Aspiration

Bone marrow aspiration

Hypercellular

Normocellular

Hypocellular

The M:E ratio

Myeloid to Erythroid ratio in the bone marrow

Is called M:E ratioNormally it is 3-4:1

Normal Blood Cells

ERYTHROPOIESISERYTHROPOIESIS

PROERYTHROBLAST

BASOPHILICERYTHROBLAST

POLYCHROMATOPHILIC ERYTHROBLAST

ORTHOCHROMATIC ERYTHROBLAST

RETICULOCYTE

MATURE ERYTHROCYTES

Stages in Red cell (erythroid)Maturation

Proerythroblast Basophilic Polychromatic Orthochromic

erythroblast erythroblast erythroblast ) two examples (

ERYTHROID PROGENITOR ERYTHROID PROGENITOR CELLSCELLS

BFU-EBFU-E: Burst Forming Unit – Erythrocyte:: Burst Forming Unit – Erythrocyte: Give rise each to thousands of nucleated Give rise each to thousands of nucleated

erythroid precursor cells, in vitro.erythroid precursor cells, in vitro.

Undergo some changes to become the Undergo some changes to become the ColonyColony Forming Units-ErythrocyteForming Units-Erythrocyte ( (CFU-ECFU-E))

Regulator: Burst Promoting Activity (Regulator: Burst Promoting Activity (BPABPA))

ERYTHROID PROGENITOR ERYTHROID PROGENITOR CELLSCELLS

CFU-ECFU-E: Colony Forming Unit- Erythrocyte:: Colony Forming Unit- Erythrocyte: Well differentiated erythroid progenitor cell.Well differentiated erythroid progenitor cell. Present only in the Red Bone Marrow.Present only in the Red Bone Marrow. Can form upto 64 nucleated erythroid Can form upto 64 nucleated erythroid

precursor cells.precursor cells. Regulator:Regulator: ErythropoietinErythropoietin..

Both these Progenitor cells cannot be Both these Progenitor cells cannot be distinguished except by in vitro culture distinguished except by in vitro culture methods.methods.

Normoblastic Normoblastic PrecursorsPrecursors

PROERYTHROBLASTPROERYTHROBLAST:: Large cell: 15 – 20 Microns in diameter.Large cell: 15 – 20 Microns in diameter. Cytoplasm is deep violet-blue stainingCytoplasm is deep violet-blue staining

HasHas no Hemoglobinno Hemoglobin.. Large nucleus 12 Microns Large nucleus 12 Microns

occupies 3/4occupies 3/4thth of the cell volume. of the cell volume. Nucleus has fine stippled Nucleus has fine stippled

reticulum & many nucleoli.reticulum & many nucleoli.

Normoblastic Precursors

EARLY NORMOBLAST:(BASOPHILIC NORMOBLAST)– Smaller in size.– Shows active Mitosis.– No nucleoli in the nucleus.– Fine chromatin network with few

condensation nodes found.– Hemoglobin begins to form.– Cytoplasm still Basophilic.

Normoblastic PrecursorsNormoblastic Precursors

INTERMEDIATE NORMOBLAST:(POLYCHROMATOPHILIC NORMOBLAST)

– Has a diameter of 10 – 14 Microns.– Shows active Mitosis.– Increased Hemoglobin content in the

cytoplasm– Cytoplasm is Polychromatophilic.

Normoblastic PrecursorsNormoblastic Precursors

LATE NORMOBLAST:(ORTHOCHROMIC NORMOBLAST)

– Diameter is 7 – 10 Microns.– Nucleus shrinks with condensed

chromatin.– Appears like a “Cartwheel”– Cytoplasm has a Eosinophilic

appearance.

RETICULOCYTE

– The penultimate stage cell.– Has a fine network of reticulum like a

heavy wreath or as clumps of dots– This is the remnant of the basophilic

cytoplasm, comprising RNA.– In the Neonates, Count is 2 – 6/Cu.mm.– Falls to <1 in the first week of life.– Reticulocytosis is the first change seen in

patients treated with Vit B12

MATURE ERYTHROCYTE

– Biconcave disc.– No nucleus.– About One-third filled with

Hemoglobin.

Erythropoiesis 4 mitotic divisions between pronormoblast and

orthochromic normoblast stage. Thus giving rise 16 RBCs. But not all of the 16 will be good RBCs, some are

bad and will be destroyed, these destroyed cells is called ineffective erythropoiesis.

2 – 7 days for pronormoblast to mature into orthochromic normoblast

1 more day to extrude the nucleus from the orthochromic normoblast.

Reticulocyte further matures for 2 – 3 days in bone marrow before it is released into the peripheral blood.

Red cell has life span of 120 days in peripheral blood.

Phases of Erythropoiesis

FACTORS REGULATINGFACTORS REGULATINGERYTHROPOIESISERYTHROPOIESIS

SINGLE MOST IMPORTANT REGULATOR: “TISSUE OXYGENATION”

BURST PROMOTING ACTIVITYERYTHROPOIETINIRONVITAMINS:

– Vitamin B12

– Folic Acid

MISCELLANEOUS

ERYTHROPOIETINERYTHROPOIETIN

A hormone produced by the Kidney.A circulating GlycoproteinNowadays available as Synthetic EpoietinActs mainly on CFU – E.Increases the number of:

– Nucleated precursors in the marrow.– Reticulocytes & Mature Erythrocytes in the

blood.

VITAMINSVITAMINS

B12: Cyanocobalamine & Folic Acid:– Is also called Extrinsic Factor of Castle.– Needs the Intrinsic Factor from the

Gastric juice for absorption from Small Intestine.

– Deficiency causes Pernicious (When IF is missing) or Megaloblastic Anemia.

– Stimulates Erythropoiesis– Is found in meat & diary products.

IRONIRON

Essential for the synthesis of Hemoglobin.

Deficiency causes Microcytic, Hypochromic Anemia.

The MCV, Color Index & MCH are low.

Regulation of ErythropoiesisRegulation of Erythropoiesis

CFU – ECFU – E

ProerythroblastsProerythroblastsMature ErythrocytesMature Erythrocytes

Tissue OxygenationTissue OxygenationFactors decreasing:Factors decreasing:

HypovolemiaHypovolemiaAnemiaAnemia

Poor blood flowPoor blood flowPulmonary DiseasePulmonary Disease

Decrease

s

ERYTHROPOIETIN

Stimulates

An example of a

Negative feed back

mechanism

Erythropoietin (Epo)As its name suggests, EPO stimulates growth of

Erythrocytes, and its function include:

Activates stem cells of bone marrow to differentiate into pronormoblasts.

Shortening cell cycle. Decrease maturation time. Increases rate of mitosis and maturation process. Increases rate of hemoglobin production. Causes increased rate of reticulocyte release into

the peripheral blood, (normally the reticulocyte when it is released to the peripheral blood it need only one day to mature to RBC, but here they will be released prematurely into peripheral blood, thus they need more than one day to mature to mature RBC.

Prevent apoptosis.

EPO receptorsFound on surface on bone marrow erythroid progenitor and precursor cells.

The highest number of EPO receptors is seen on the CFU-E and the pronormoblasts.

The number of EPO receptors per cell gradually decreases during erythroid cell differentiation, and studies have shown that the reticulocyte and mature erythrocyte do not contain EPO receptors

EPO ReceptorDivided into extracellular, transmembrane, and cytoplasmic domains.

The cytoplasmic domain has terminal that contains both positive and negative growth-regulatory domains.

After EPO binding, EPOR homodimarizes and JAK-2 phosphorylates itself, so EPOR and other proteins like STAT-5 initiate the cascade of proliferative signals.

GranulopoiesisGranulopoiesis

N

E

B

GranulocytesGranulocytesNeutrophilsNeutrophils

EosinophilsEosinophils

BasophilsBasophils

Only mature cells are present in Only mature cells are present in peripheral bloodperipheral blood

Stages in GranulocyteMaturation

Blast cell Promyelocyte Myelocyte Metamyelocyte Band cell Segmented Neutrophil

Neutrophil Maturation - MyeloblastNeutrophil Maturation - Myeloblast

Cells in the BM proliferation pool take 24-48 hours for a single cell cycle

Less than 1% of the normal BM compartment is composed of myeloblasts

Large, 15-20 um in sizeDelicate nucleus with prominent nucleoliSmall amount of cytoplasm with rough

endoplasmic reticulum, a developing Golgi apparatus and an increasing number of azurophilic granules

Neutrophil Maturation - MyeloblastNeutrophil Maturation - Myeloblast

Cytochemical staining shows presence of myeloperoxidase which is required for intracellular kills

Killing function is the first to be operational in the neutrophil cell line

Myeloblast is incapable of motility, adhesion and phagocytosis and is therefore nonfunctional

Neutrophil Maturation - PromyelocyteNeutrophil Maturation - Promyelocyte

After a few days in the blast stage, the cell becomes a promyelocyte

1-5% of BM compartment composed of promyelocytes

Size is variable and may exceed 20 um, so may be larger than myeloblast

Nuclear chromatin may be delicate or may show slight clumping

Nuceloli begin to fade

Stages in GranulocyteMaturation

Blast cell Promyelocyte Myelocyte Metamyelocyte Band cell Segmented Neutrophil

Neutrophil Maturation - MyelocyteNeutrophil Maturation - MyelocyteProduction and accumulation of neutrophilic

granules is characteristic of the myelocyte

The myelocyte is the last cell of the BM compartment capable of mitosis

Myelocytes demonstrate morphologic variability as this development stage lasts from 4-5 days and cause alterations in the staining characteristics of the cell

Neutrophil Maturation - MyelocyteNeutrophil Maturation - MyelocyteSmaller in size than the promyelocyte (12-18 um)

Less than 10% of BM compartment is made up of myelocytes

Nucleus is round to oval with a flattened side near the now well-developed Golgi apparatus

Nuclear chromatin shows clumping

Nucleoli no longer visible

Stages in GranulocyteMaturation

Blast cell Promyelocyte Myelocyte Metamyelocyte Band cell Segmented Neutrophil

Neutrophil Maturation - MyelocyteNeutrophil Maturation - Myelocyte

Secondary granules stain pink causing a “dawn of neutrophilia” or pink blush within the cytoplasm

Compounds such as alkaline phosphatase begin to concentrate in the cell

The cell acquires some motility

Granulopoiesis

Notice change in Notice change in granules colorgranules color

Neutrophilic Maturation - MetamyelocyteNeutrophilic Maturation - Metamyelocyte

13-22 % of BM compartment10-15 um in sizeNot seen in normal PBNot fully functional, part of the maturation

component of the marrow

Neutrophilic Maturation - BandNeutrophilic Maturation - Band

The band is a transitional form that exists in both the PB and the BM and considered part of both the maturation and storage pools

Up to 40% of the WBCs of the BM are bands

Represents the “almost mature” neutrophil having full motility, active adhesion properties, and some phagocytic ability

Neutrophilic Maturation - BandNeutrophilic Maturation - BandBand forms begin to produce tertiary

granulesMembrane maturity shows changes in

cytoskeleton, surface charge and presence of receptors for complement

Once entered into the PB, account for less than 6% of circulating WBCs

10-15 um in sizeFound in marginating and circulating pools

of the PB

Neutrophilic Maturation - PMNNeutrophilic Maturation - PMNThis cell’s nucleus continues to indent until

thin strands of membrane and heterochromatin form into segments, hence it is also called a “seg”

Polymorphonuclear means “many-shaped nucleus”, describing the varied nuclear shapes

Cell is completely functional and spend time in the storage pool of the BM as well as marginating and circulating pools of the PB

50-70% of circulating WBCs of PB

Neutrophilic Maturation - PMNNeutrophilic Maturation - PMNPMNs spend their life performing

phagocytosis and pinocytosisPhagocytosis involves larger

material and can be observed with light microscopy, pinocytosis involves small material (liquids) and is observed with EM

Both of these function can be performed in the circulation of the blood stream or in the tissues

Neutrophil kinetics

Monocyte/Macrophage MaturationMonocyte/Macrophage MaturationMonocyte/Macrophage cells mature from

monoblast to promonocyte to blood monocyte to free and fixed macrophages, but the mechanism of commitment is not well understood.

Granular content vary considerably with more than 50 secretory compounds having been identified.

PB monocytes demonstrate morphologic variability

Aggressive motility and adherence may distort the monocytes during PB smear preparation

Monocyte/Macrophage MaturationMonocyte/Macrophage Maturation

Monocyte nucleus is indented or curved with chromatin that is lacy with small clumps

Typically the largest cell in the PBCytoplasm is filled with minute granules

that produce a cloudy appearanceCytoplasmic membrane may be

irregular, pseudopods and phagocytic vacuoles may be evident

Monocyte/Macrophage MaturationMonocyte/Macrophage Maturation

LymphocytesLymphocytesThe only human WBCs whose site of

development is not just BM, but also tissues referred to as primary and secondary lymphoid organs

In humans, the primary lymphoid organs are the thymus and bone marrow, the secondary organs include the spleen, Peyer’s patches of the GI tract, the Waldermyer ring of the tonsils and adenoids, the lymph nodes and modules scattered throughout the body

LymphocytesLymphocytesLymphocytes circulate throughout the body

in both PB and lymph which act as carrier streams to bring the lymphocytes to sites of activity

Lymphocytes migrate from thoracic duct through vessel endothelium to lymph nodes to blood stream and back.

Lymphocytes are categorized in a variety of ways and may be short-lived or long-lived cells

Lymphocytes may produce antibodies or lymphokines and have different surface charges, densities and antigen receptors.

Lymphocytes - DevelopmentLymphocytes - DevelopmentThe PSC results in a stem cell for

the lymphoid cell (CFU-L) as a result of hormonal stimuli

The CFU-L matures in several environments

Thymus and BM give rise to lymphocytes, foster differentiation and are indepentendent of antigenic stimulation

Lymphocytes - DevelopmentLymphocytes - Development

Lymphocyte % in the PB varies, depending on age.

Children under the age of 4 have a higher proportion of lymphocytes in the PB than do adults

Lymphocytes are the second most common WBC of the PB making up 20-40% of WBCs.

20-35% of circulating lymphocytes are B cells

Lymphocytes - MaturationLymphocytes - MaturationLymphoblast to prolymphocyteLymphoblast is small, 10-18 umRound to oval nucleusLoose chromatin with one or more active

nucleoliScanty cytoplasmProlymphocyte difficult to distinguish,

subtle changes, more clumped chromatin, lessening nucleolar priminence, change in thickness of the nuclear membrane

LymphopoiesisLymphopoiesis

ThrombopoiesisThrombopoiesisPlatelet play a major

role in primary hemostasis

Life span 7-10 daysProduction,

fragmentation of cytoplasm

Megakaryocytes undergoes endomitotic division

1/3 in spleen

The role of cytokines in

Megakaryocytopoiesis

The effect of IL-1on target cells & Tissues

SummarySummary

Normal haemopoiesis is necessary for the survival

It is under the control of multiple factors

Normal bone marrow environment is necessary for normal haemopoiesis

Decreased production results in cytopenias

HematopoiesisHematopoiesis

Just notice general trends,Don’t memorize

Maturation SequenceMaturation Sequence

Notice general trends,

Don’t memorize

Monophyletic theory of cell Monophyletic theory of cell formationformation