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Myelopoiesis

Phagocytes are specialized in destruction of foreign
materials; thus they have a fundamental role in body's
defense against invasion by micro -organisms,
destruction of tumor cells and ingestion of apoptotic
cells.
Phagocytes are classifi ed into:

1. polymorph nuclear: neutrophils, eosinophils and

basophils.
2. mononuclear: monocytes and macrophages.

Neutrophils:

 They are found in bone marrow, blood and
tissues.
 They are the most numerous phagocy tes as
normal range is 2.5 -7.5 × 10 9/L; constituti ng
about 65% of circulating leukocytes in man.
 About 50% of neutrophils in blood marginate
to the wall of vessels and they are not
represented in blood count; demarginating in
response to infection, exercise and steroid
treatment.
 Their half life in blood is short about 12 -24
hours; after that they enter tissues where die
after 1 -2 days.
 They are easily identified in blood smear
when stained with Romanovsky stain by
characteristic segmented nucleus and pale
pink cytoplasm filled with indistinct violet
colo red granules.

Neutrophilia:

It is a neutrophils count more than 7.5 ×10 9/L; it's
causes are:
1. Infection: e.g. bacterial.
2. Inflammation: e.g. autoimmune diseases, gout and
tissue necrosis.
3. Neoplasia: any malignancy.
4. Metabolic conditions: e.g. uremia and acidosis.
5. Hemorrhage and hemolysis.
6. Corticosteroids.
7. Bone marrow infiltration.
8. Myeloproliferative disorders.

Neutropenia:

It is a neutrophils count less than 2 ×10 9/L; it's causes
are:
1. Racial.
2. Congenital ( Kost man's syndrome ).
3. Cyclical neutrope nia.
4. Hypoplastic marrow; paroxysmal nocturnal
hemoglobinurea.
5. Bone marrow infiltration.
6. Megaloblastic anemia.
7. Some acute infections: e.g. typhoid fever and
military TB.
8. Drugs: e.g. anti -arrhythmic (amiodarone), anti -
convulsant (phenytoin).
9. Exposure to radi ation.
10 . Immune disorders: e.g. idiopathic, drugs, HIV
and infection.
11 . Hypersplenism.

Eosinophils:

 They are minor type of granulocytes as normal
range is 0.04 -0.4 ×10 9/L constituting about 1 -
4% of circulating leukocytes.
 Their half life in blood is about 3-8 hours.
 They are larger than neutrophils and
characterized by numerous large cytoplasmic
granules which stained deeply with acidic
dyes like eosin.

Causes of eosinophilia:

1. Infection: e.g. parasitic.
2. Inflammation: e.g. Polyarteritis nodosa.
3. Allergy: e. g. atopy ; drug sensitivity.
4. Neoplasia: e.g. Hodgkin's and non -Hodgkin's
lymphomas
5. Myeloproliferative disorders.
6. Hyper -eosinophilic syndrome.

Basophils:

 Their normal range is 0.01 -0.1 ×10 9/L
constituting about 0.2 -1% of circulating
leukocytes.
 Their half l ife in blood is about 2.5 days.
 Mature basophils have multi -lobed nuclei and
contain numerous prominent granules which
stained purple with blue aniline dyes.

Causes of basophilia:

1. Infection : pox virus.
2. Inflammation:
3. Metabolic conditions: e.g. Myxedema.
4. Myeloproliferative disorders.

Monocytes:

 Their normal range in blood is 0.2 -0.8 ×10 9/L
constituting about 5% of circulating
leukocytes.
 Their half life in blood is about 17 hours
 They have a non -segmented nucleus of
variable shapes (round, oval, notched or
folded) with abundant grayish blue cytoplasm.

Causes of monocytosis:

1. Infection: e.g. TB.
2. Inflammation: e.g. systemic lupus erythematosus
and rheumatoid arthritis.
3. Neoplasia: Chronic myelo -monocytic leukemia
(most common cause).

Lymphocytes:

 There are 3 types of lymphocytes (T -cells, B -
cells and natural killer cells)
 Their normal range in blood is 1 -3 ×10 9/L
constituting 20 -40% of circulating leukocytes.
 B- lymphocytes are the precursors of antibody
producing cells.
 T- lymphocytes:
1. provide signals induc ing B - and T -cells
proliferation and differentiation.
2. specifically delete virally infected cells
and foreign cells.
3. act as effecter cells association with
macrophages.
4. participate in the antigen -specific
selection of lymphocytes .
 NK cells kill abnormal sel f and foreign cells
that fail to express on normal self class II MCH
on their surface.

Causes of lymphocytosis:

1. Neoplasia: e.g. chronic lymphocytic leukemia,
lymphoma and hairy cells leukemia.
2. Others:
 Infection: Viral (HIV and mumps); Bacterial
(typhoid f ever and pertusis); Protozoal
(toxoplasmosis).
 Serum sickness.

Causes of lymphopeni a:

1. Infection: Influenza virus and septicemia.
2. Lymphocytes loss as in lymphatic fistula.
3. Drugs: e.g. anti -lymphocytes globulin (ALG).
4. Neoplasia: e.g. metastatic carcinoma.
5. N utritional: e.g. folate and B 12 deficiency.
6. Others: systemic lupus erythematosus.


رفعت المحاضرة من قبل: Ahmed monther Aljial
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