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PHAGOCYTIC LEUKOCYTES
NEUTROPHIL
Maturation series:
Myeloblast
Promyelocyte
Myelocyte
Metamyelocyte
Band
Segmented Neutrophil
NEUTROPHIL – CONT.
Stage Nucleus Cytoplasm Others
Myeloblast - Smooth, lacy chromatin pattern- 2 or more nucleoli
Dark blue-blue
1-2% of BM cells
Promyelocyte - Immature, uniform chromatin pattern
Dark blue- blue
-2-5% of BM cells- 10 granules
Myelocyte -More condensed- nucleoli not visible
Loses cytoplasmic RNA
-“dawn of neutrophilia”- last stage of mitosis- 20 granules- 10-20% of BM cells
NEUTROPHIL – CONT.
Stage Nucleus Cytoplasm Others
Metamyelocyte (Juvenile)
- Identified by shape of nucleus - Kidney bean or peanut shaped- Coarsely clumped chromatin
-All traces of RNA is lost- pink with pinkish-purple 20 granules
-15-20% of BM cells- indentation of nucleus < half its width
Band (Stab) - curved, band shaped without a threadlike filament
- Pinkish tan with fine granules
- 5-10% in peripheral blood
Segmented Neutrophil
- 2-4 lobes - Pinkish tan with fine granules
- 37-77% (adults)- 2-6.93 x 109/L- 3-4 x 109/L (children)
Lifespan: 9-10 days 3 areas of the body:
Mitotic Pool
Maturation & Storage Pool
Circulating Pool
Marginal Pool
NEUTROPHIL – CONT.
Regulatory Mechanism:Colony-stimulating factors
(Leukopoietin)Sources:
MacrophagesActivated T cellsEndothelial cellsFibroblasts
Increased release by:Bacterial endotoxinphagocytosis
NEUTROPHIL – CONT.
Granule Contents:
NEUTROPHIL – CONT.
Promyelocyte stage Membrane-bound lysosomes (acid
hydrolases) Constituents:
myeloperoxidase (MPO) lysozyme (muramidase)proteases
Primary or Azurophilic Granules
NEUTROPHIL – CONT.
Lysozymes Lactoferrin Specific collagenases Vit. B12-binding proteins NO PEROXIDASE
Secondary Granules
NEUTROPHIL – CONT.
Gelatinase Alkaline phosphatases Late myelocyte stage
Tertiary Granules
NEUTROPHIL – CONT.
Function:Phagocytosis
5 steps:1.Motility2.Recognition3.Ingestion4.Degranulation5.Killing
NEUTROPHIL – CONT.
1. Motility- resembles hand mirror when in motion- “glass” (lamellopod)- “handle” (narrow tail of cytoplasm)
Random migration Directed migration (chemotaxis)
C5a endotoxins
NEUTROPHIL – CONT.
2. Recognition Opsonins (Gk : to prepare for dining)
IgG C3, aided by IgM Fibronectin (GP in plasma and outer
membrane of fibroblast & endothelial cells)
NEUTROPHIL – CONT.
3. Ingestion- Formation of phagosome
4. Degranulation- cytoplasmic granules fuse with phagosome
NEUTROPHIL – CONT.
5. Killing
active O2 metabolism
superoxide anion (O-) H2O2
Acid environment
TOXIC
NEUTROPHIL – CONT.
superoxide anion (O-) H2O2
Superoxide dismutase
Catalase
NEUTROPHIL – CONT.
Disorders of phagocytosis: Chediak-Higashi syndrome Drugs (corticosteroids) Ethanol Systemic diseases (eg: RA, uremia, MM, SLE, DM)
Testing of Neutrophil Function: Boyden micropore filter technique Rebuck skin window procedure Nitroblue tetrazolium test (NBT)
NEUTROPHIL – CONT.
EOSINOPHIL
Stimulated by multi-CSF or IL3 Specific granules (orange)
Higher conc’n of peroxidase Major basic protein (rich in arginine & lysine)
Charcot-Leyden crystals Many eosinophils disintegrate in exudates/secretions Hexagonal bipyrimidal crystals Found in: nasal mucus (asthmatic pxs)
pleural fluid (pulmonary eosinophilic infiltrates)
stool (parasitic infections)
BASOPHIL
Least common Mast cells – resemble basophils Functions:
Phagocyte Involved in inflammatory response
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