CELLS INVOLVES IN IMMUNITY UTTARAN MODHUKALYA 1

CONTENT 1. INTRODUCTION 2. HEMATOPOIETIC STEM CELL 3. LYMPHOCYTE CELL 4. MYELOID CELL 5. REFERENCE 6. CONCLUSION 2

INTRODUCTION Immunity is the ability of the body to protect against all types of foreign bodies like bacteria, virus, toxic substance etc. Immunity is of two types i.e, innate and acquired immunity. Innate immunity is inherited by the organism from the parents and protect it from birth throughout life and The immunity that an individual acquires after birth is called adaptive or acquired immunity. The cells involves in immunity are originated from bone marrow(bursa of fabricius in case of bird) and thymus where each cell having different function to protect the body against the antigenic substance. 3

HEMATOPOIETIC STEM CELL All the blood and lymphoid cell arise from a type of cell called hematopoietic stem cell. Then this cell differentiated into myeloid progenitor cell and lymphoid progenitor cell. 4

HEMATOPOIETIC STEM CELL Further the lymphoid progenitor cell differentiated into B-cell, T- cell, Natural killer cell and dendritic cell. On the other hand the myeloid progenitor cell is differentiated into eosinophil, basophil, neutrophil, macrophage, mast cell and dendritic cell, erythrocyte, platelets. The lymphoid cell are central cell that directly involve in immunoresponse. 5

LYMPHOCYTE CELL Lymphocyte constitute 20-40% bodies WBC cells and 99% of the cells in the lymph. The lymphocyte constantly circulate in the blood and lymph. On the basis of function and cell membrane components lymphocyte can be divided into three types- 1. B- lymphocyte 2. T- lymphocyte 3. Natural Killer cell 6

B-LYMPHOCYTE CELL This type of cell directly involved in immunoresponse. B-cell originate from the organ Bursa of fabricius in bird and bone marrow in mammals through the lymphoid progenitor cell. When B lymphocytes is mature then it produce antibody so, this immunity is called antibody mediated or humoral immunity. Formation of plasma B-cell and memory B-cell : When antibodies on B-cell’s surface bind antigen the B-cell is activated and produced daughter B-cell which later give rise to plasma B-cell and memory B-cell. This phenomenon is called clonal selection. 1. Plasma cell: It become enlarged and secrete enormous amounts of body and lives only for few days. 2. Memory B-cell : It remains as memory cell and having longer life span. 7

T-LYMPHOCYTES CELL T-lymphocyte originated in the bone marrow but develop in the thymus. T-cell also have membrane receptors for antigen which are not structurally similar to antibody. This receptor are called T-cell receptor(TCR) which doesn't recognised free antigen. They recognise antigen bound to MHC proteins. Displayed on cell surface. It is of two types- T H- cell(T helper cell) and T c -cell(T cytotoxic cell). T H- cell helps phagocytic to kill microbes and help B-cells to make antibodies against that microbes. T c -cell kill infected cell of the body and eliminated the reservoir of infection. 8

NATURAL KILLER CELL Natural killer cell are large granular lymphocytes constitute about 5-10% of total lymphocytes. NK cells differentiated in bone marrow, thymus, spleen, lymph nodes etc. It kills the cells infected by virus through blocking replication of virus. NK cells doesn't express receptor like B-cell, T-cell. Their cytoplasm contain perforin and protease. 9

MYELOID PROGENITOR CELL It develops monocytes(dendritic cell, mast cell and macrophage), granulocytes (basophil, eosinophil, neutrophil) etc. A] Granulocytic cell: The granulocyte cell include basophil, eosinophil, neutrophil. They produced in the bone marrow through the myeloid progenitor cell. 1. Neutrophil: The neutrophil are active phagocytic cells They have multilobed nucleus % of WBC are neutrophil. They target the bacterial and fungal antigens and kill them either by phagocytosis. 10

MYELOID PROGENITOR CELL 2]Eosinophil: They constitute 1 to 6% of total WBC. They have bilobbed nucleus and 8 to 12 days of life span. They carryout degranulation reaction, release enzyme, growth factors and cytokines. They are involved in reaction again parasites and allergic substances. 3]Basophil: Their percentage in WBC is less than 1. They release histamine, enzyme, cytokines which are involved in body defence. 11

MYELOID PROGENITOR CELL Monocytes: 1] Mast cell: The mast cell are involved in allergic reaction, composition in total WBC for mast cell is very low. 2] Dendritic cell: The dendritic cells have elongated extension. They may be produced from myeloid progenitor or lymphoid progenitor. Their main function in adaptive immunity is as a antigen presenting cell. 12

FIG : LYMPHOID AND MYELOID CELL CLASSIFICATION 13

MECHANISM ANTIGEN MACROPHAGE ANTIGEN PRESENTING CELL HELPER T-CELL B-CELL MEMORY T-CELL CYTOTOXIC T-CELL PLASMA B-CELL MEMORY B-CELL KILL INFECTED CELL 14

CONCLUSION From the above discussion we have concluded that various types of cells are involved when a microbes/pathogen enters to our body. Mainly we can say that some cells are involved to go against pathogen directly e.g, Macrophage. Some are involved against pathogen infected cell for kill e.g, cytotoxic T-cell. Some cells help to kill pathogen to other cell e.g, Helper T cell. Some cell produces antibody directly i.e, plasma B- cell 15

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