HAEMATOPOIESIS

The miracle of a life sustaining fluid---blood!

By- Francis Prathyusha,

MScd endo2nd sem-2nd yr-
 Blood ??
Hematopoiesis is the production of blood cells, a
developmental process located in the (red)bone
marrow, though some cells mature elsewhere.
 Hide Notes fr slide 2
• Humans can't live without blood. Without blood,
the body's organs couldn't get the oxygen and
nutrients they need to survive and maintain the
normal function operation; we couldn't keep
warm or cool off, fight against infections, or get
rid of our own metabolite waste products.
Without enough blood, we'd weaken and die.
Blood is a major factor in life-sustaining. A
deficiency in the supply or quality of blood will
impair the quality of life .Therefore, the nature of
the blood is the fundamental basis for health
 Immune system

• It has ability to distinguish self from non-

self
• It has ability to neutralize or inactivate
foreign bodies
• The immune system is intimately
connected with the hematologic system
since white blood cells (leukocytes,
including B- and T-lymphocytes) are key
players in the lymphoid system.
 Haematopoiesis

• Ancient Greek
• αἷμα, "blood"; ποιεῖν "to make"
• hematopoiesis in the United States;
sometimes also
haemopoiesis or hemopoiesis
 3 weeks fetus, yolk sac of the first to take up
the responsibility of hematopoiesis

6 weeks fetus, liver starting to take up blood

formation

3 months fetus , the spleen

is the main blood-forming
organs
 hide Notes -7
• Each of the human body's blood is produced
by the body itself, not from the maternal
blood into the fetal blood vessels. Human
embryonic hematopoietic began in the 3rd
weeks, at this stage there is only little organ
formation, an embryonic tissue called the yolk
sac.
Hematopoiesis
The process of haematopoiesis
• The process of haematopoiesis occurs
in several stages, and is controlled by
at least 11hematopoietic growth
factors (including the colony-
stimulating factors, IL-2 through IL-
7,G-CSF, GM-CSF, and M-CSF).
• stem → progenitor → precursor →
adult → mature
 Hide notes 10
• The first stage involves the differentiation of
a pluripotential stem cell into a committed
progenitor, which is followed by maturation of
committed progenitors in distinct pathways, in
which precursors are partially developed,
'adolescent' cells en route to maturity.
 Hematopoietic stem cells
• (HSCs) reside in the medulla of the bone
(bone marrow) and have the unique
ability to give rise to all of the different
mature blood cell types.
Haematopoietic stem cells
 Hide notes - 13
• A stem is an unspecialize cel that’s is capable of replicating or self
renewing itself and developing into specilaized cells at a variety of
cell types.
• The product of a stem cell undersgoing division is atleast one
additional stem cell that has the same capabilities of the originating
cell.
• 2nd generation stem cell and neuron
• A prog or precrsr is an unspeIalised cell or has partial characteristics
of a spec cel that is capable of undergoing cell div and yeilding 2
specialized cells ..

• Every functional specialized mature blood cell is derived from a

common stem cell. These stem cells are therefore, PLURIPOTENT.
Conti..
• HSCs can be isolated by using florescence-
labeled antibodies to mark specific cell
surface antigens and florescence activated
cell sorting (FACS)instrument.
 Hide notes 15
• Relationship between several of the characterized
hematopoietic stem cells and early progenitor cells.
Differentiation is indicated by colors; the more intense the
color, the more mature the cells. Surface marker
distinctions are subtle between these early cell
populations, yet they have clearly distinct potentials. Stem
cells can choose between self-renewal and differentiation.
Progenitors can expand temporarily but always continue to
differentiate (other than in certain leukemias). The mature
lymphoid (T-cells, B-cells, and Natural Killer cells) and
myeloerythroid cells (granulocytes, macrophages, red
blood cells, and platelets) that are produced by these stem
and progenitor cells
HSCs are studied using experimental
techniques that permits analysis of
hemopoiesis invitro and invivo
 Hide notes 17
• In vivo techniques include injecting the bone marrow of
normal donor mice into lethally irradiated mice whose
hematopoietic cells have been destroyed. In these animals,
the transplanted bone marrow cells develop colonies of
hematopoietic cells in the spleen
• In vitro techniques involve the use of a semisolid tissue
culture medium made with a layer of cells derived from
bone marrow stroma (stroma is the supporting tissue). This
medium creates favorable micro environmental conditions
for hematopoiesis. Data from several experiments show
that under these favorable micro environmental conditions,
stimulation by growth factors influences the development
of the various types of blood cells
 Slide 20
• HSCs are self renewing: when they proliferate,
at least some of their daughter cells remain as
HSCs, so the pool of stem cells does not
become depleted. The other daughters of
HSCs (myeloid and lymphoid progenitor cells),
however can each commit to any of the
alternative differentiation pathways that lead
to the production of one or more specific
types of blood cells, but cannot self-renew.
This is one of the vital processes in the body.
 All blood cells are divided into three
lineages.
1. -Erythroid cells are the oxygen carrying red blood cells. Both
reticulocytes and erythrocytes are functional and are released into
the blood. In fact, a reticulocyte count estimates the rate
of erythropoiesis.

2. -Lymphocytes are the cornerstone of the adaptive immune system.

They are derived from common lymphoid progenitors. The lymphoid
lineage is primarily composed of T-cells and B-cells (types of white
blood cells). This is lymphopoiesis.

3. -Myelocytes, which include granulocytes, megakaryocytes and

macrophages and are derived from common myeloid progenitors,
are involved in such diverse roles as innate immunity, adaptive
immunity, and blood clotting. This is myelopoiesis.
 Hide notes 22
• Granulopoiesis (or granulocytopoiesis) is
haematopoiesis of granulocytes.

• Megakaryocytopoiesis is haematopoiesis
of megakaryocytes.
 MEDICAL APPLICATION
Growth factors have been used clinically to increase
marrow cellularity and blood cell counts. The use of
growth factors to stimulate the proliferation of
leukocytes is opening broad new applications for
clinical therapy. Potential therapeutic uses of growth
factors include increasing the number of blood cells
in diseases or induced conditions (eg, chemotherapy,
irradiation) that result in low blood counts,
increasing the efficiency of marrow transplants by
enhancing cell proliferation, enhancing host defenses
in patients with malignancies and infectious and
immunodeficient diseases, and enhancing the
treatment of parasitic diseases.
• Hematopoietic diseases are usually caused
by suppression or enhancement of some
undifferentiated cell production, with a
consequent reduction or overproduction of
hematopoietic cells.
• In some diseases, however, suppression
and enhancement of proliferation of more
than one type of stem cell can occur,
sequentially or simultaneously. In such
cases, there are reduced numbers of some
cell types (eg, aplastic anemia, a disorder
characterized by decreased production of
hematopoietic cells) coinciding with
increased numbers of others (eg, leukemia,
the abnormal proliferation of leukocytes)
 Hide notes 27
• The initial experiments with normal bone
marrow transplanted to irradiated mice
established the basis for bone marrow
transplantation, now frequently used to treat
some disorders of hematopoietic cell
proliferation
Bone Marrow
 Hide notes- 30
• Under normal conditions, the production of blood cells by the bone
marrow is adjusted to the body's needs, increasing its activity
several-fold in a very short time. Bone marrow is found in the
medullary canals of long bones and in the cavities of cancellous
bones . Two types of bone marrow have been described based on
their appearance on gross examination: red, or hematogenous,
bone marrow, whose color is produced by the presence of blood
and blood-forming cells; and yellow bone marrow, whose color is
produced by the presence of a great number of adipose cells. In
newborns, all bone marrow is red and is therefore active in the
production of blood cells. As the child grows, most of the bone
marrow changes gradually into the yellow variety. Under certain
conditions, such as severe bleeding or hypoxia, yellow bone marrow
is replaced by red bone marrow.
 Red bone marrow
• RBM composed of a stroma (from Greek,
meaning bed), hematopoietic cords, and
sinusoidal capillaries. The stroma is a three-
dimensional meshwork of reticular cells and
a delicate web of reticular fibers containing
hematopoietic cells and macrophages. The
stroma of bone marrow contains collagen
types I and III, fibronectin, laminin, and
proteoglycans. Laminin, fibronectin, and
another cell-binding substance, hemonectin,
interact with cell receptors to bind cells to
the stroma. The sinusoids are formed by a
discontinuous layer of endothelial cells.
• An external discontinuous layer of reticular
cells and a loose net of reticular fibers
reinforce the sinusoidal capillaries. The
release of mature bone cells from the
marrow is controlled by releasing factors
produced in response to the needs of the
organism. Several substances with releasing
activity have been described, including the
C3 component of complement (a series of
immunologically active blood proteins),
hormones (glucocorticoids and androgens),
and some bacterial toxins.
Drawing showing the passage of erythrocytes, leukocytes, and platelets across a sinusoid
capillary in red bone marrow. Because erythrocytes (unlike leukocytes) do not have
sufficient motility to cross the wall of the sinusoid, they are believed to enter the sinusoid
by a pressure gradient that exists across its wall. Leukocytes, after the action of releasing
substances, cross the wall of the sinusoid by their own activity. Megakaryocytes form thin
processes that cross the wall of the sinusoid and fragment at their tips, liberating the
platelets.
Red Bone Marrow
 Hide notes 34
• Section of active bone marrow (red bone
marrow) showing some of its components.
Five blood sinusoid capillaries containing
many erythrocytes
• Note the thinness of the blood capillary wall.
Giemsa stain. Medium magnification.
Red Bone Marrow
Bone Marrow As a Source of Stem
Cells for Other Tissues
 MEDICAL APPLICATION

• Red bone marrow is rich in stem cells

that can produce several tissues, not
just blood cells. With their great
potential for differentiation, these
cells make it possible to generate
specialized cells that are not rejected
by the body because they are
produced from stem cells from the
marrow of the same person.
 Hide notes 38
• The procedure is to collect bone marrow stem
cells, cultivate them in appropriate medium to
direct their differentiation to the cell type needed
for transplantation, and then use the cells
originating in tissue culture to replace the cells
needed by the patient. In this case the donor and
the recipient are the same person and the
histocompatibility is complete, excluding the
possibility of rejection. Even though these studies
are just beginning, the results so far are
promising.
 Origin and differentiative stages of
blood cells

The pluripotent stem cells proliferate and form 2 major cell lineage
 Hide notes 40
• The proliferating stem cells form daughter
cells with reduced potentiality. These
unipotential or bipotential progenitor cells
generate precursor cells (blasts) in which the
morphological characteristics differentiate for
the first time, suggesting the mature cell types
they will become. In contrast, stem and
progenitor cells cannot be morphologically
distinguished and resemble large lymphocytes
 Maturation of Erythrocytes
• A mature cell is the one that has
differentiated to the stage at which it
can carry out all its specific functions.
• Erythrocyte maturation involves
hemoglobin synthesis and formation
of a small, enucleated, biconcave
corpuscle.
Erythrocyte maturation
 Hide notes 43
• Thre r 5 intervening cell divisions between proerythrob – erythcyte
• 1-proery– is a large cell with loose, lacy chrmatin,nucleoli and basophilic
cytoplasm.
• Basophilic re- basophilic cytoplasm and a condensed nucl with no visible nucleolus
• Polychromotophilic eryth- polyribosomes decrease, and areas of the cytoplasm
begin to be filled with hemoglobin. At this stage, staining causes several colors to
appear in the cell—the polychromatophilic (Gr. polys, many, + chroma, color, +
philein, to love) erythroblast.
• orthochromatophilic - the nucleus continues to condense and no cytoplasmic
basophilia is evident, resulting in a uniformly acidophilic cytoplasm—the
orthochromatophilic (Gr. orthos, correct, + chroma + philein) erythroblast.
• At a given moment, this cell puts forth a series of cytoplasmic protrusions and
expels its nucleus, encased in a thin layer of cytoplasm. The expelled nucleus is
engulfed by macrophages. The remaining cell still has a small number of
polyribosomes that, when treated with the dye brilliant cresyl blue, aggregate to
form a stained network. This cell is the reticulocyte, which soon loses its
polyribosomes and becomes a mature erythrocyte.
 Hide notes 46
• Several changes takes place – cell and nuclear volume decrease –
nucleoli deminish in size and disappear .. The chromatin –denser
until the nucleus presents a pyknotic appearance and is finally
extruded from the cell..
• Thre is a gradual decrese in the number of polyribosomes
(basophilia decreases) with a simultaneous increase in the amount
of hemoglobinwith in the cytoplasm .. Mitichondria and other
organels grad decrese
• Summary of erythrocyte maturation. The stippled part of the
cytoplasm (on the left) shows the continuous increase in
hemoglobin concentration from proerythroblast to erythrocyte.
There is also a gradual decrease in nuclear volume and an increase
in chromatin condensation, followed by extrusion of a pyknotic
nucleus. The times are the average life span of each cell type. In the
graph, 100% represents the highest recorded concentrations of
hemoglobin and RNA.
Pararosaniline–toluidine blue (PT)
stain. High magnification.
 Hide notes 47
• Section of red bone marrow showing an
immature megakaryocyte in the upper right
corner. There is also a large group of
erythropoietic cells (delimited by a broken
line) and sparse immature neutrophils
(arrowheads).
Electron micrograph of red bone
marrow.
 Hide notes 49
• Four erythroblasts in successive stages of
maturation are seen (E1, E2, E3, and E4). As
the cell matures, its chromatin becomes
gradually condensed, the accumulation of
hemoglobin increases the electron density of
the cytoplasm, and the mitochondria (M)
decrease in number. x11,000.
Giemsa stain. High magnification.
 Hide notes 52
• A megakaryocyte in mitosis (center)
surrounded by erythropoietic cells with a
mitotic figure (arrowhead). The arrow
indicates an erythroblast extruding its
nucleus.
Granulopoiesis
 Hide notes 53
• The maturation process of granulocytes takes place with cytoplasmic
changes characterized by the synthesis of a number of proteins that are
packed in two organelles: the azurophilic and specific granules. These
proteins are produced in the rough endoplasmic reticulum and the Golgi
complex in two successive stages ..
• 1st stage results in the production of the azurophilic granules, which stain
with basic dyes in the Wright or Giemsa methods and contain enzymes of
the lysosomal system.
• 2nd stage, a change in synthetic activity takes place with the production
of several proteins that are packed in the specific granules. These granules
contain different proteins in each of the three types of granulocytes and
are utilized for the various activities of each type of granulocyte. Evidently,
a shift in gene expression occurs in this process, permitting neutrophils to
specialize in bacterial destruction and eosinophils and basophils to
become involved in the regulation of inflammation.
Maturation of granulocytes
 Hide notes 55
• The myeloblast is the most immature recognizable cell in the
myeloid series. It has a finely dispersed chromatin, and nucleoli can
be seen promyelocyte (L. pro, before, + Gr. myelos, marrow, + kytos,
cell) is characterized by its basophilic cytoplasm and azurophilic
granules. These granules contain lysosomal enzymes and
myeloperoxidase. The promyelocyte gives rise to the three known
types of granulocyte. The first sign of differentiation appears in the
myelocytes, in which specific granules gradually increase in quantity
and eventually occupy most of the cytoplasm.
• These neutrophilic , basophilic, eosinophilic myelocytes mature
with further condensation of the nucleus and a considerable
increase in their specific granule content. Before its complete
maturation, the neutrophilic granulocyte passes through an
intermediate stage in which its nucleus has the form of a curved rod
(band cell). This cell appears in quantity in the blood after strong
stimulation of hematopoiesis.
Neutrophilic myelocyte from normal human
bone marrow treated with peroxidase.
 Hide notes 58
• At this stage, the cell is smaller than the
promyelocyte, and the cytoplasm contains two
types of granules: large, peroxidase-positive
azurophilic granules (AG) and smaller specific
granules (SG), which do not stain for peroxidase.
Note that the peroxidase reaction product is
present only in azurophilic granules and is not
seen in the rough endoplasmic reticulum (RER) or
Golgi cisternae (GC), which are located around
the centriole (C). N, nucleus. x15,000. (Courtesy
of DF Bainton.)
 MEDICAL APPLICATION

• The appearance of large numbers of

immature neutrophils (band cells) in the
blood is called a shift to the left and is
clinically significant, usually indicating
bacterial infection.
Kinetics of Neutrophil
Production
 Hide notes 61
• The medullary formation compartment can be subdivided into a mitotic compartment (3 days) and
a maturation compartment (4 days).
• A medullary storage compartment acts as a buffer system, capable of releasing large numbers of
mature neutrophils on demand. Neutrophils remain in this compartment for about 4 days.
• The circulating compartment consists of neutrophils suspended in plasma and circulating in blood
vessels.
• The marginating compartment is composed of neutrophils that are present in blood but do not
circulate. These neutrophils are in capillaries and are temporarily excluded from the circulation by
vasoconstriction, or—especially in the lungs—they may be at the periphery of vessels, adhering to
the endothelium, and not in the main bloodstream.
• The marginating and circulating compartments are of about equal size, and there is a constant
interchange of cells between them. The half-life of a neutrophil in these two compartments is 6–7
h. The medullary formation and storage compartments together are about 10 times as large as the
circulating and marginating compartments.
• Neutrophils and other granulocytes enter the connective tissues by passing through intercellular
junctions found between endothelial cells of capillaries and postcapillary venules (diapedesis). The
connective tissues form a fifth compartment for neutrophils, but its size is not known. Neutrophils
reside here for 1–4 days and then die by apoptosis, regardless of whether they have performed
their major function of phagocytosis.
 MEDICAL APPLICATION
Thus, neutrophilia, an increase in the number of
neutrophils in the circulation, does not necessarily
imply an increase in neutrophil production.
Intense muscular activity or the administration of
epinephrine causes neutrophils in the marginating
compartment to move into the circulating
compartment, causing an apparent neutrophilia
even though neutrophil production has not
increased.
The neutrophilia that occurs during the course of
bacterial infections is due to an increase in
production of neutrophils and a shorter duration
of these cells in the medullary storage
compartment. In such cases, immature forms
such as band cells, neutrophilic metamyelocytes,
and even myelocytes may appear in the
bloodstream.
Maturation of Lymphocytes &
Monocytes
 Hide notes 65
• Monocytes
• The monoblast is a committed progenitor cell that is almost
identical to the myeloblast in its morphological characteristics.
Further differentiation leads to the promonocyte, a large cell (up to
18 m in diameter) with a basophilic cytoplasm and a large, slightly
indented nucleus. The chromatin is lacy, and nucleoli are evident.
Promonocytes divide twice in the course of their development into
monocytes. A large amount of rough endoplasmic reticulum is
present, as is an extensive Golgi complex in which granule
condensation can be seen to be taking place. These granules are
primary lysosomes, which are observed as fine azurophilic granules
in blood monocytes. Mature monocytes enter the bloodstream,
circulate for about 8 h, and then enter the connective tissues,
where they mature into macrophages and function
Maturation of Lymphocytes
& Monocytes
 Hide slide 67
• Lymphocytes
• The first identifiable progenitor of lymphoid cells is the lymphoblast, a large cell
capable of incorporating [3H]thymidine and dividing two or three times to form
prolymphocytes. Prolymphocytes are smaller and have relatively more condensed
chromatin but none of the cell-surface antigens that mark prolymphocytes as T or
B lymphocytes. In the bone marrow and in the thymus, these cells synthesize cell-
surface receptors characteristic of their lineage, but they are not recognizable as
distinct B or T lymphocytes in routine histological procedures. Using
immunocytochemical techniques makes the distinction.
• Circulating lymphocytes originate mainly in the thymus and the peripheral
lymphoid organs (eg, spleen, lymph nodes, tonsils). However, all lymphocyte
progenitor cells originate in the bone marrow. Some of these lymphocytes migrate
to the thymus, where they acquire the full attributes of T lymphocytes.
Subsequently, T lymphocytes populate specific regions of peripheral lymphoid
organs. Other bone marrow lymphocytes differentiate into B lymphocytes in the
bone marrow and then migrate to peripheral lymphoid organs, where they inhabit
and multiply in their own special compartments.
MEDICAL APPLICATION
• Leukemias are malignant clones of leukocyte
precursors
• They occur in lymphoid tissue (lymphocytic
leukemias) and in bone marrow
(myelogenous and monocytic leukemias).
In these diseases, there is usually a release of
large numbers of immature cells into the
blood.
• The symptoms of leukemias are a
consequence of this shift in cell proliferation,
with a lack of some cell types and excessive
production of others (which are often
abnormal in function). The patient is usually
anemic and prone to infection.
• A clinical technique that is helpful in
the study of leukemias and other
bone marrow disturbances is bone
marrow aspiration.
 Hide slide 70
• A needle is introduced through compact bone
(usually the sternum), and a sample of marrow is
withdrawn..
• The sample is spread on a microscope slide and
stained. The use of labeled monoclonal
antibodies specific to proteins in the membranes
of precursor blood cells aids in identifying cell
types derived from these stem cells and
contributes to a more precise diagnosis of the
various types of leukemia.
 Origin of Platelets
• In adults, platelets originate in the red
bone marrow by fragmentation of the
cytoplasm of mature megakaryocytes
(Gr. megas, big, + karyon, nucleus, +
kytos), which, in turn, arise by
differentiation of megakaryoblasts.
Megakaryoblasts &
Megakaryocytes
 Hide notes - 73
• Megakaryoblasts is 15–50 m in diameter and has a large ovoid or kidney-shaped
nucleus with numerous nucleoli. The nucleus becomes highly polyploid (ie, it
contains up to 30 times as much DNA as a normal cell) before platelets begin to
form. The cytoplasm of this cell is homogeneous and intensely basophilic.
• The megakaryocyte is a giant cell (35–150 m in diameter) with an irregularly
lobulated nucleus, coarse chromatin, and no visible nucleoli. The cytoplasm
contains numerous mitochondria, a well-developed rough endoplasmic reticulum,
and an extensive Golgi complex. Platelets have conspicuous granules, originating
from the Golgi complex, that contain biologically active substances, such as
platelet-derived growth factor, fibroblast growth factor, von Willebrand's factor
(which promotes adhesion of platelets to endothelial cells), and platelet factor IV
(which stimulates blood coagulation). With maturation of the megakaryocyte,
numerous invaginations of the plasma membrane ramify throughout the
cytoplasm, forming the demarcation membranes (Figure 13–20). This system
defines areas of a megakaryocyte's cytoplasm that shed platelets, extruding them
into the circulation.
 Section of bone marrow

• Section of bone marrow showing various stages of megakaryocyte

development (1–4), several adipocytes (*), and blood sinusoids
(arrowheads). PT stain. Medium magnification
Electron micrograph of a
megakaryocyte
 Hide notes 78
• Electron micrograph of a megakaryocyte
showing a lobulated nucleus (N) and
numerous cytoplasmic granules. The
demarcation membranes are visible as tubular
profiles. x4900. (Reproduced, with permission,
from Junqueira LCU, Salles LMM: Ultra-
Estrutura e Função Celular. Edgard Blücher,
1975.)
 MEDICAL APPLICATION

• In certain forms of thrombocytopenic

purpura, a disease in which the number
of blood platelets is reduced, the
platelets appear to be bound to the
cytoplasm of the megakaryocytes,
indicating a defect in the liberation
mechanism of these corpuscles. The life
span of platelets is approximately 10
days.
Summary