Cells of the immune system | Online Biotech Notes

Cells of the immune system:

WBC or leukocytes are divided into three categories:

1. Lymphocytes
2. Monocytes
3. Granulocytes --  dedritic

LYMPHOCYTES:-

• 20-30 population
• B cells
• T cells
• Natural killer cells

A). B-Lymphocyte-

1. Site of maturation

• Bursa of fabriscus in birds
• Bone marrow in mammals 

2. membrane bound immunoglobulin

3. Once antigen is encountered.

    Differentiation

•  Plasma cells – antibody can be secreted die within 1-2 weeks.
• Memory7 B cells – some membrane bound antibody as present B cells longer life span.

B). T-Lymphocytes:-

1. Site of maturation

• Thymus

2. T cells receptor

• Only recognize antigen that is bound to cell membrane proteins called major histocompatibility complex (MCH).
• Once antigen in encountered with MHC differentiation;

                a). Effectors  T cells 

                b). Memory T cell

3. 2 subpopulations 

• i). T helper (TH)
• ii). T cytotoxic (TC)
• iii). And now T regulatory(Treg)

                a). T helper cells:- 

• CD4 glycoprotein
• Help activation of B cells Tc cells macrophages in immune response

                b). T cytotoxic cells:-

• CD8 glycoprotein 
• It is called cytotoxic T lymphocytes 
• Eliminates injected cells or cancerous cells

                c). T regulatory cells:-

• CD4+, CD25+ & fox P3+ receptor.
• Help suppress the immune system.

C). Natural killer cells:-

• Innate immune response
• Large, granular
• Recognize tumor or virus – infected cells.
• CD16 – which can recognize a region of antibody that has attached to cell infected by virus?
• Monocytes  (mononuclear phagocytes)

1. Mononuclear phagocytes 
2. Monocytes circulate in blood and then migrate into tissue and differentiate into specific macrophages.

                     a). Distribution of macrophage

• Intestinal macrophage in gut 
• Alveolar macrophages in lung.
• Histiocytes in connective tissue.
• Kupffer cells in the liven.
•  Mesangail cells in the kidney.
• Microglial cells in the brain.
• Osteoclasts in bone.

                    b).Function of macrophage;-

• The primary function of the macrophage is to promote phogocytosis.
• Macrophage id used as antigen presenting cell & present the antigen to T-cells via MHC.

Granulocytes: -

Granulocytes contain large granule in their cytoplasm which is visible under light microscope & according to their granules present in their cytoplasm it is divided into three cell type:-

1. Neutrophils
2. Eosinophils
3. Basophils  

Cells of Immune System

Neutrophils:- 

• Multi lobed nucleus, light granules.
• 1st to arrive at site of inflammation.
• High neutrophils us 1st indication of infection (acute infection)
• Phagocytosis.
• Generate antimicrobial agents

Eosinophils:-

Eosinophils, like neutrophils are motile phagocytic cells that can migrate from the blood into the tissue spaces. They play a role in the defense against parasitic organisms. The secreted content of eosinophilic granules (Basic protein) may damage the parasite membrane.

Basophils:-

• Basophils are nonphagocytic granulocytes that function by releasing pharmacologically active substances (histamine) these substances play major role I certain allergie responses.  

Dendritic cell:-

• Long membranous extensions, look like dendrites on nerve cells.
• Antigen presentation via MHC.
• 4 major groups;-
• Langerhans DC
• Interstitial DC
• Monocyte – derived DC
• Plasmacytoid derived DC
• Following Dendnitic cell
• Involved with B cell maturation.