Cells of the immune system, Overview of immune cells. Immune cells

Overview of immune cells,

1. Cells of THE immune system BY A.MANOJ KUMAR

2. ABBREVATION Ag - Antigen Ab - Antibody MHC - Major Histocompatibility Complex NK - Natural Killer Cell Ig - Immunoglobulin APC - Antigen Presenting Cell PMNs - Polymorphonuclear leucocyte CD - Cluster of Differentiation Fc - Crystalizable fragment WBC - White Blood Cell

3. CELLS OF THE IMMUNE SYSTEM The immune system operates by producing immune cells. The immune cells arise from Haematopoietic Stem cells from where they differentiate into many types of cells.

4. LYMPHOID CELLS Lymphocytes are the central cells of the immune system responsible for adaptive immunity. The Lymphocytes are active based on 4 immunological atritute such as Antigenic Specificity Antibody Diversity Immunological memory Self / Non-self Recognition

5. Lymphocytes constitute 20-40 % of the bodies WBC There are approximately 10 cells of Lymphocytes present in human body. B CELLS B cells origin and mature within the bone marrow, When they leave it ,each cells are expressed a unique Ag binding receptor on the surface of the B cells. This binding or B cell receptor is membrane bound antibody molecules.

6. When a native B cells (The one that has not previously encound Antigen) The binding of Ag- Ab complex causes the cell to divide rapidly and differentiate into plasma B cell and memory cell. PLASMA CELLS Plasma B cells produces Ab is secreted form and produce enormous amount of more than 2000 molecule per second / cells B cells forms the basics of Humoral mediated or Ab mediated Immune response

7. The plasma cells can stay only for a few days or weeks Plasma B cells are the cells that generated during primary immune Response The markers present in the B cells are B220,B7-1,B7-2,CD40. MEMORY CELLS Memory B cells are generated during Primary immune Response and reproduce the same membrane bound Ab molecule during the Secondary immune Response

8. T CELLS T Lymphocytes origin from bone marrow and migrate to thymus gland for maturation During maturation T cell express its Unique antigen binding molecule called T-cell receptor , on its surface membrane Unlike B cells which can directly can recognize the Ag alone, But T cells receptor can recognize the Ag bound with cell membrane protein called MHC molecule expressed by APC or all Nucleated cells.

9. When the naive T cells encound the antigen in the secondary organ , that is complexed with class 1 & 2 MHC molecule, the T cell divides / proliferate and differentiate into plasma T cells and Memory cells The plasma T cell further differentiate into a helper T cell and Cytotoxic T cell. The helper T cell and Cytotoxic T cell can be distinguish based on the marker present on the surface of the cells T-Helper cell display CD4 marker T- cytotoxic cell display CD8 marker

10. Natural killer cells Natural killer cells is a large granular Lymphocytes that have cytotoxic actitivity against the tumour cells It constitute 5-10% of the human blood Enhance do not express membrane molecule or receptor like B & T cell receptor Against the tumour Ag specific Ab mediated immune response develops, such complex (Tumour Ag- Ab ) binds to Fc receptor of NK cells.

11. Eg -NK Cell Expresses CD16 receptor,a membrane receptor on the surface of NK cell for the carboxyl terminal end of Ig G molecule such a process of cytotoxicity is called ADCC ( Antibody Dependent Cell-Mediated Cytotoxicity MYELOID CELLS Mononuclear phagocytes- 1.Monocytes 2.Macrophage Polymorphonuclear Leukocytes 1.Eosinophil,2.Basophil,3.Neutrophil,4.Mast cell,5.Dendritic Cell

12. MACROPHAGE Stem cell bone marrow Monocyte Progenitor cells Promonocytes Which leave the bone marrow and circulate in blood for 8hrs,where they mature into monocytes Then,they enlarge migrate into tissue and differentiate into tissue specific macrophage

13. Macrophage serve different function in different tissue and are named according to their location Lung - Dust cells Connective tissue - Histocytes Liver - Kupffer cells Kidney - Mesangial cells Brain - Microglial cells Bone - Osteoclasts

14. Role of Macrophage Macrophages act as the APC and help activation of T cells( Both T H& C cells) It involved phagocytosis

15. Opsonization The rate of phagocytosis of Ag was fold 4000-fold higher in the presence of specific Ab. Here the antibody function as opsonin the entire process called Opsonization The complex of Ag- Ab binds the Antibody receptor on the membrane of the macrophage and phagocytosis is enhance

16. Poly morpho nuclear Leukocytes (PMNs) PMNs or Granulocytic cells are classified into 1.Eosinophil, 2.Basophil, 3.Neutrophil, 4.Mast cell, 5.Dendritic Cell . based on the cellular morphology of the cell, cytoplasmic staining characteristic

17. NEUTROPHILS Neutrophils has a multilobed nucleus and granulated cytoplasm It constitute 50-70% of the circulating WBC Neutrophils origin from bone marrow and circulate in the blood for 7-10 hrs before migrating to the tissue These cells are the first arrive at the site of inflammation, resulting in the increase the no of circulating Neutrophils , called leukocytosis

18. It is used medically as a indication of infection Granules contain 1.primary granules- Peroxidase , lysozyme , Hydrolytic enzyme 2.Secondary Granule- Collagenase , Lactoferrin,lysozyme

19. EOSINOPHILS Eosinophil like neutrophil are motile phagocytic cell Its originate from bone marrow and circulate in the blood and migrate into tissue It constitute 1-3% of circulating WBC It has bilobed nucleus and granulated cytoplasm that stains with eosin dye that is called Eosinophils It place the major role in the defence against parasitic infection

20. BASOPHILS Basophils are non- phagocytic granulocytes. It consitute less than1 % of the total circulating WBC. Thy play a major role in certain allergic response. The granules present in the basophils contain pharamacologically active substance

21. MAST CELL It originates from the bone marrow and released into the blood as undiffrentiated cell and differentiated into mast cell in tissue The mast cell can be found in skin, connective tissue of various organ, mucosal epithelial tissue of respiratory and digestive track It plays a major role in Allergic reaction It contains large cytoplasmic granule , which contain histamine and pharamacologically active substance

22. DENDRITIC CELLS It is an APC that process the antigen into antigenic peptide and form a complex with MHC class 1 &2 molecule and present it into the T cell for the T- H & C cell activation It is origin from Haematopoietic stem cell There are 4 types of Dendritic cells 1.Laugerham cell 2.Interstitial Dendritic cells 3.Myeloid cells 4.Lymphoid Dendritic cells

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