The document discusses the origin and development of blood cells through the process of hematopoiesis. It describes how hematopoietic stem cells in the bone marrow differentiate into the various blood cell lineages through regulated stages of proliferation and maturation. Key points covered include the major sites of hematopoiesis, growth factors involved in lineage commitment and differentiation, and the morphological changes that occur as progenitors mature into red blood cells, white blood cells, platelets or megakaryocytes. The process of hematopoiesis is tightly controlled to maintain blood cell homeostasis.

1. ORIGIN & DEVELOPMENT OF BLOOD CELLS
Varun Kumar Singh

2. Defination : “The processes involved in the production of all of the various cells of the blood
from the HSCs are collectively called hematopoiesis”
 Highly regulated process -- to maintain circulating cell numbers within relatively constant
levels and to respond rapidly to conditions requiring extra cells .
 Maintains balance between self-renewal, terminal differentiation, migration, and cell
death.

3.  3 wk : formation of blood islands from yolk
sac
 Primitive hematopoiesis
 Definitive hematopoietic tissue
 LTR-HSC (produce all lineages)
 6 wk : liver becomes hematopoietic organ
 6-8 wk : spleen (until 8th month)
 12-14wk : bone marrow (life-long)

5.  Bone marrow/Medullary Hematopoiesis
In children :
 Axial skeleton:
 Cranium
 Ribs.
 Sternum
 Vertebrae
 Pelvis
 Appendicular skeleton:
 Bones of the Upper & Lower limbs
In Adults in:
• The axial skeleton
• The proximal ends of the appendicular skeleton.

6.  Liver
 Spleen
 Thymus
 Lymphnodes

7.  Hematopoietic stem cells
 Progenitor cells
 Maturing cells

8.  -0.5% of total hematopoietic precursor cells
 Multilineage differentiation potential
 Population maintained by self renewal
 Quiescent cell population
 Stable population size
 Not morphologically recognizable

9.  3% of total HPC
 Restricted developmental potential
 Multipotential – unipotential
 Transit population with restricted self renewal
 Population amplified by proliferation.
 Not morphologically recognizable

10.  >95%
 Transit population, numerically amplified by proliferation
 Proliferative sequence completes before full maturation
 Morphologically recognizable

12. Pluripotent Stem cells:
 Has a diameter of 18 – 23 μ.
 Giving rise to: both Myeloid and Lymphoid series of cells
 Capable of extensive self-renewal.
Myeloid Stem cells:
 Generate myeloid cells:
 Erythrocytes
 Granulocytes: PMNs, Eosinophils & Basophils.
 Megakaryocytes
Lymphoid Stem cells:
 Lymphocytes - B, T cells, Plasma cells, NK cells

14. Cellular Extra cellular
•Adipocytes
•Endothelial cells
•Fibroblasts
•T- cells
•Macrophages
•Soluble factors – cytokines, GF
•ECM – collagen, GAGs,
cytoadhesion molecules
•Expression of homing
receptors.
•GFs
•Membrane proteins
•ECM components
•Regulation of HSC, PGC
differentiation
•Structural support
•Cell – cell interactions
•Adhesion of precursors to ECM
proteins

16.  Glycoprotein hormones
 Regulate
 proliferation , differentiation and survival of haemopoietic precursor cells
 the function of mature blood cells.
 Source : T lymphocytes, monocytes, marcrophages and stromal cells.
except for :
 erythropoietin, (90% synthesized in kidney)
 thrombopoietin, (liver)

17.  Multiple biological activities (Pleiotrophy)
 Similar or identical activities ( redundancy )
 Individually – poor, function – interplay of several GFs together
 Interact with membrane receptors - lineage specific
 Requirements change during differentiating process
 Affect hematopoiesis directly or indirectly
 Act synergistically with other cytokines

18. Growth factors
Early acting ( Multilineage)
GF
Late acting ( Lineage Restricted)
GF
• stem cell factor and Flt3 ligand
•IL-3 & GM-CSF
•IL-6 & IL-11
•G-CSF
•M-CSF
•EPO
•TPO
•IL-5
•IL-2,4,7,10,12,13,14,15

19.  GM-CSF
Granulocyte-Macrophage colony stimulating factor
 M-CSF
Macrophage colony stimulating factor
 Erythropoietin
Erythropoiesis stimulating hormone
(These factors have the capacity to stimulate the proliferation of
their target progenitor cells when used as a sole source of
stimulation)
 Thrombopoietin
Stimulates megakaryopoiesis

20.  Quiescent state of stem cells
 Oppose the actions of positive regulators
 Includes –
 Interferons
 TGF-β – Induces apoptosis
 TNF – inhibits all CFUs
 PGEs – inhibit granulopoiesis and monopoiesis
 Acidic isoferritins
 Lactoferrin - from mature neutrophils – feedback inhibition
 Di OH vitamin D3
 T and NK cells
 SCI/MIP 1α - inhibit stem cells

21.  Surface receptors
 With cytoplasmic tyrosine kinase domain
 M-CSF, SCF, FL
 HGF Receptor superfamily – no intrinsic kinase activity
 IL3, IL5, GM-CSF
 IL6, IL11
 IL 2/4/7/9/13/15
 Functional redundancy

22. Local environmental control
Stromal cell mediated Haemopoiesis
Haemopoietic
growth factors (Humoral regulation)Apoptosis
There should be a balance between cell production and cell death except at the times of requirement

25. BFU-E: Burst Forming Unit – Erythrocyte:
 Give rise each to thousands of nucleated erythroid precursor
cells, in vitro.
 Undergo some changes to become the Colony Forming Units-
Erythrocyte (CFU-E)
 Regulator: Burst Promoting Activity (BPA)

27. Stage Morphology
Pronormoblast •20-25 microns
•Mitosis present
•Nucleus with multiple nucleoli
•Basophilic cytoplasm- polyribosomes
•No hemoglobin
Basophilic normoblast •16-18 microns
•Large nucleus
•Perinuclear halo
•Basophilic cytoplasm
•Active mitosis
Polychromatophilic normoblast •10-15 microns
•Chromatin lumps
•Hb starts appearing
•Reduced mitoses

28. Orthochromatic normoblast •10-15 microns
•Small and pyknotic nucleus
•Pink- salmon cytoplasm
•Mitoses absent
Reticulocyte •Reticular nuclear fragments
•Nucleus extruded
•Slightly larger than RBCs
Erythrocyte •7.5m in diameter
•Anucleate
•Salmon color

29. ERYTHROPOIESIS
15-20µm- basophilic cytoplasm, nucleus with
nucleoli.
14-17µm-mitosis, basophilic cytoplasm, nucleoli
disappears.
10-15µm-’POLYCHROMASIA’
Hb appears, nucleus condenses.
7-10µm- PYKNOTIC Nucleus.
Extrusion, Hb is maximum.
7.3µm- Reticulum of basophilic material in the
cytoplasm.
7.2µm- Mature red cell with Hb.

30.  MOST IMPORTANT REGULATOR :
“TISSUE OXYGENATION”
 ERYTHROPOIETIN
 IRON
 VITAMINS:
 Vitamin B12
 Folic Acid
 MISCELLANEOUS

33. Leukopoiesis
Myelopoiesis
Neutrophil Eosinophil Basophil Monocyte
Lymphopoiesis
Lymphocyte

35. Granulocyte Maturation
• Includes neutrophils, eosinophils, basophils
• Regulated by IL-3,GM-CSF, G-CSF
• Bone Marrow: Four stages,
– Most granulocytes are neutrophils;
• Marrow & Blood: Immature band form
– Normal to low % of band neutrophils in the blood
– An increased %of immature neutrophils in the blood(e.g, bands, metas) is called a
‘left shift’
• Blood: Mature segmented form
• Short lifespan, 1-2 days after marrow release

36. Size (µm) Nucleus Cytoplasm N:C ratio Granules CD
markers
Matura
tion
transit
time
Myeloblast
(0.2-1.5)
14-20 Round-oval ,
delicate lacy
chromatin,
nucleoli
Deep blue High Absent CD13,33,
34,38
1 day
Promyelocyte
(2-4)
15-21 Round- oval,
more
condensed
than blast,
nucleoli
Deep blue High Large, reddish purple,
primary (azurophilic)
CD33,38 1-3
days
Myelocyte (8-
16)
12-18 Round-oval,
chromatin
more
condensed
Light pink, blue
patches
Decreased Small pink red, (specific
granules)
Azurophilic granules,(dec)
secretory vesicles.
1-5
days
Metamyelocyt
e (9-25)
10-18 Kidney bean
shape,
condensed
chromatin
pink decreased Small pink red specific
granules, few azurophilic,
secretary vesicles
0.5-4
days
Band (9-15) 9-15 Horse shoe
shaped
Pink Decreased Abundant small pink red
specific granules, few
azurophilic, secretory
vesicles, tertiary granules
0.5-4
days
Polymorphon
uclear ( 6-12)
9-15 Segmented, 2-
4 lobes
pink Decreased As in band CD 15,
16,11b,18
1-5 days

38. CD9
CD11a
CD13
GM-CSF
IL-3
IL-5
9 Days
12-15µ

39. CD9
CD11a
CD13
IL-3
GM-CSF
SCF
IL-4, IL-5
10-
15µ
2.5-7 Days

42. Characteristics Basophils Mast cells
origin CD34+, C-KIT- , HSC CD34+,C-KIT+ ,stem cells
Site of maturation Bone marrow, circulate in blood,
normally not found in tissues
tissue
Proliferative potential no yes
Life span days Weeks to months
size Small (10-15µm) large
Nucleus
Processes
Granules
Multilobed
Blunt
Few,small(peroxidase +ve)
Unilobed
Large(acid & alk phosphatase +ve)
Key cytokine IL-3 SCF
Surface receptors
IL-3-R
C-kit-R
IgE –R
Present
Absent
Present
Absent
Present
Present

43. GM-CSF
IL-3
M-CSF

44. Monocytopoiesis
MONOBLAST •Large cell (15-25 )
•Nucleus oval
•Cytoplasm without granule or few azurophlic
granule
•Differentiate to the Promonocyte
PROMONOCYTE Divide twice in the course of their
development into monocytes
MONOCYTE •Mature monocytes enter the
bloodstream, circulate.
then enter the connective tissues,
where they mature into macrophages.
•CD 11b,13,14,15
Macrophage •CD 68

45. Lymphoblast Prolymphocyte Lymphocyte

48. CD 19 CD 24
Surface Ig R

54. Developmental stages of megakaryocytes
Name Characteristics
STAGE 1 MEGAKARYOBLAST  6-24 microm in diameter
 Scant strongly
basophilic cytoplasm
 no visible granules
 Minimally lobed
nucleus
 Visible nucleoli
STAGE 2 PROMEGAKARYOCYTES Also k/a basophilic
megakaryocyte
14-30µm diameter
Partly lobulated nucleus
Increased cytoplasm
Few azuroplic cytoplasm
granules
Beginning of demarcation
membranes

55. STAGE 3 GRANULAR
MEGAKARYOCYTE
25-50mm, diameter
Low N/C ratio
Large multilobed
nucleus
Acidophilic cytoplasm
No visible nucleoli
 Numerous azurophilic
granules
STAGE 4 MATURE
MEGAKARYOCYTES
 40-60µm diameter
 Multiple nuclei,
occasionally pyknotic
 Azurophilic
granules-in groups
 Functionally active

56. • Devoid of cytoplasm
• Ingested by macrophages

57. PPSC CFU- GEMM
IL 3 & 6 , 11
IL-3 & GM-CSF
CFU- MEGA
IL-3 , TPO
TPO
MEGAK’BLAST
MATURE
FUNCTIONING
MEGA
IL-6 and IL-11 act in syn
IL-3
Maturation of
megakaryocytes
Increases platelet
production
No effect on
ENDOMITOSIS
TPO is primary regulater of
thrombopoiesis
Also k/a mpl ligand or
(MGDF)
MAJOR physiologic regulator
of megakaryocyte proliferation
and platelet production
Influences all stages
Tpo levels are inversely prop
to platelets counts
7days

59. PHSC CSC Diff. Compartment Circulation
<------ Proliferation --------------------->
Differentiation -------------------->
Maturation ----------------------->
Release ------------------------->
PHSC = Pluripotent hemopoietic stem cells
CSC = Committed stem cells

61. CD34, SCF-R, TPO-R

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