Phagocytic Leukocytes

PHAGOCYTIC LEUKOCYTES

NEUTROPHIL

Maturation series:

Myeloblast

Promyelocyte

Myelocyte

Metamyelocyte

Band

Segmented Neutrophil

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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

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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

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Regulatory Mechanism:Colony-stimulating factors

(Leukopoietin)Sources:

MacrophagesActivated T cellsEndothelial cellsFibroblasts

Increased release by:Bacterial endotoxinphagocytosis

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Granule Contents:

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Promyelocyte stage Membrane-bound lysosomes (acid

hydrolases) Constituents:

myeloperoxidase (MPO) lysozyme (muramidase)proteases

Primary or Azurophilic Granules

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Lysozymes Lactoferrin Specific collagenases Vit. B12-binding proteins NO PEROXIDASE

Secondary Granules

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Gelatinase Alkaline phosphatases Late myelocyte stage

Tertiary Granules

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Function:Phagocytosis

5 steps:1.Motility2.Recognition3.Ingestion4.Degranulation5.Killing

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1. Motility- resembles hand mirror when in motion- “glass” (lamellopod)- “handle” (narrow tail of cytoplasm)

Random migration Directed migration (chemotaxis)

C5a endotoxins

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2. Recognition Opsonins (Gk : to prepare for dining)

IgG C3, aided by IgM Fibronectin (GP in plasma and outer

membrane of fibroblast & endothelial cells)

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3. Ingestion- Formation of phagosome

4. Degranulation- cytoplasmic granules fuse with phagosome

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5. Killing

active O2 metabolism

superoxide anion (O-) H2O2

Acid environment

TOXIC

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superoxide anion (O-) H2O2

Superoxide dismutase

Catalase

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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