Histology of Agranulocytes |Histology|


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Ok this will be the last post on Histology for Heamopoeitic and Lymphatic System.
This post will concentrate in discussing on histology of agranulocyes; Monocyte and Lymphocyte
I will discuss separately for both cell so it would be easy for us to understand their characteristics

Lymphocytes

Introduction
1) Contained a very huge nucleus located at the center of the cell
2) Due to the huge size of nucleus, the cytoplasm is somehow pushed to the periphery giving its distinctive shape of a blue rim
3) The nucleus has a dense heterochromatin
4) Some evident of azurophilic granule presence
5) Its not functional in bloodstream, but elicit its response in connective tissue
6) Produced in red marrow, mature at connective tissue
7) Once it is competent enough, it will undergo mitosis to produce identical progeny cells
8) All members of a particular clone will only act on the same antigen the mother cell responded before
9) Appear in small number in connective tissue but rather increase during chronic inflammation

Types of Lymphocytes
1) T-lymphocytes
+80% of total lymphocytes
+Lifespan of few months
+Function primarily in CELLULAR IMMUNITY
+Migrate from red marrow and mature at THYMUS
+Subtypes of T-lymphocytes
-T-killer cells/cytotoxic cells
+destroy viral infected cells or cancer cells
+T-helper cells
-Initiate response and development of response
+T-suppressor
-Suppressed immune response
2) B-lymphocytes
+15% of total lymphocytes
+Lifespan of at most 5years
+Function primarily in HUMORAL IMMUNITY
+Migrate from red marrow and mature at BURSAE FIBRICIOUS (not at bone marrow like most of us think off)
+Differentiated into PLASMA CELLs to produce antibodies to fight against antigens
3) Null cells
+5% of total lymphocytes
+It is a type of circulating stem cell
+Give rise to
-Formed elements
-Natural killer (NK) cells
4) Memory cells
+Do not involve in any immunological response
+Use to keep memory so that it will mount immediate response during future exposure

Formation
Lymphocytes always follow the Lymphoid Heamotopoeisis pathway. There is a slightly different in the development of lymphocyte in regard to other cells in which the progenitor cell gives rise to precursor cell which name with “cyte” at the compared to other cell which normally having “blast” at its end. Belo is the diagram of lymphocyte development :-

Pluripotent Heamapoeitic Stem Cell –> CFU-Lymphocyte –> CFU-Lymphocyte T/Lymphocyte B –> T/B lymphocyte –> T/B lymphoblast –> T/B Lymphocyte

Monocyte

Introduction
1) The largest blood cell in the circulating bloodstream
2) Has considerable amount of azurophilic granules which stained blue
3) No specific granules
Nucleus is accentric, kidney shaped, and having coarse chromatin network
4) Once enter the tissue it will form MACROPHAGE
5) Circulate the blood only for few days, then migrate to tissue

Formation
Monocyte shares the same progenitor cell with neutrophil which is CFU-GM. Below is the diagram for monocyte development:-

Pluripotent Heamopoeitic Stem Cell –> CFU-S –> CFU-GM –> CFU-Monocyte –> Promonocyte –> Monocyte

This is the last Histology post on Heamopoeitic and Lymphatic System.
I do hope it helps you even a bit.
Goodluck!
Thanks again =)

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