Histology of Neutrophil |Histology|


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Now it is time for us to discuss on immunocytes.
I will try to simplify the characteristics of all types of immunocytes but rather in this post I will be concentrating in Neutrophils.
Below is the simplification of immunocytes

1) Neutrophils
+Granular cytoplasm, neither being stained by eosin nor hemotoxylin – reflects its name ‘neutrophils’ – neutral
+Multi-lobulated nuclei
2) Eosinophils
+Large pink granules – stained by eosin; acidophilic
+Sausage-like nucleus
-Nuclear projection links between the two lobes
3) Basophils
+Dense dark blue granules – stained by hemotoxylin; basophilic
+Nucleus is somehow hidden behind the dense cytoplasmic granules
4) Monocytes
+Largest of all leukocytes
+Accentric kidney-like nucleus
+Lack of granule, thus agranulocyte
5) Lymphocytes
+Single, large, centrally located nucleus
+With narrow rim of cytoplasm

Those are few general ideas on leukocytes. Now let us concentrate on the Neutrophils.

Introduction
1) The most abundant leukocytes in blood
2) Light pink cytoplasm
3) Lots of azurophilic granules (a dye used to stain neutrophilic granules, since they can’t be stained by either eosin or hemotoxylin)
4) Dark blue, coarse nucleus
5) Multi-lobulated nucleus, having 2 to 3 lobes
6) Upon activation, becomes highly motile and phagocytic
7) Once phagocytosed foreign materials, it will die and form the main constituent of pus

Maturation of Neutrophils
1) Nascent neutrophils do not have lobule in their nucleus, thus called as STAB CELLS
2) Increased in the number of stab cells in circulation indicates increased in the production of neutrophils, perhaps due to bacterial infection.
3) Below is supposed to be the normal range of neutrophils in the peripheral blood.

1) Neutrophilic metamyelocyte – 0-0.5%
2) Neutrophilic stab cell – 3-5%
3) Neutrophil – 40-70%

Neutrophilic Granules
1) Primary granules called azurophilic granules
+The same to that of lysosome of other cells
+First granules to appear
+Upon maturation, their numbers drop
+Dense dark
2) Secondary Granules
+Specific granules to neutrophils
+Two time numerous compared to primary granules
+Very light in color
+Contained
-Collagenase type IV
-Lysozyme
-Phogocytin

Formation

Neutrophil shares the same progenitor cell with Monocyte which is CFU-GM. The formation of neutrophil is controlled by numerous cytokines especially Colony Stimulating Factor (CSF). Below is the diagram of Leukocytopoeisis:-

Pluripotent Heamopoeitic Stem Cell –> CFU-S –> CFU-GM –> CFU-G –> Myeloblast –> Promyelocyte –> Neutromyelocyte –> Stab cells –> Neutrophils

Function

Neutrophil is a polymorphonuclear phagocyting cell. Once activated, it can survive in anaerobic condition due to its abundant content of glycogen granules for anaerobic respiration.
Below is the process on how neutrophil engulfs foreign particles

1) On the surface there are receptors which used to bind to antigens.
2) Once an antigen binds to the receptor, neutrophil creates pseudopodia thru assembly and disassembly of actin.
3) The pseudopodia fuse and surrounds the particle.
4) The foreign particle will fuse into a vesicle call phagosome.
5) Phagosome will fuse with primary granule containing lysosomal enzymes.
6) Enzyme will then degrade the particle
7) The degraded particle will form residual body

That is all about neutrophils. You can further on it, it would be very nice to know in detail.
Until then, thanks!!

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