Cells of the immune system

Cells of the immune system The immune system is composed of many interdependent cells that protect the body from microbial infections and the growth of tumour cells. The cellular composition of adult human blood is given in Table . . Table . The cellular composition of adult human blood Cell type Number of cells per µl Approximate percentage Red blood cells , - , - White blood cells Agranulocytes Lymphocytes - - Monocytes - - Granulocytes Neutrophils - - Basophils - < Eosinophils - - Platelets , - , - All these cells are derived from pluripotent haematopoetic stem cells. Each stem cell has the capacity to produce RBC, WBC and platelets. The mucosa-associated lymphoid tissue (MALT) is a diffuse system of small concentrations of lymphoid tissue in the alimentary, respiratory and urino-genital tracts. MALT is populated by lymphocytes such as T and B cells, as well as plasma cells and macrophages, each of which is well situated to encounter antigens passing through the mucosal epithelium. It also possesses IgA antibodies. Gut-associated lymphoid tissue (GALT) is a component of the mucosa- associated lymphoid tissue (MALT) which works in the immune system to protect the body from invasion in the gut. Bronchus Associated Lymphoid Tissues (BALT) also a component of MALT is made of lymphoid tissue (tonsils, lymph nodes, lymph follicles) is found in the respiratory mucosae from the nasal cavities to the lungs. XII Std Zoology Chapter XII Std Zoology Chapter Immunology The only cells capable of specifically recognising and producing an immune response are the lymphocytes. The other types of white blood cells play an important role in non specific immune response, antigen presentation and cytokine production. Lymphocytes About - % of the white blood cells are lymphocytes. They have a large nucleus filling most of the cell, surrounded by a little cytoplasm. The two main types of lymphocytes are B and T lymphocytes. Both these are produced in the bone marrow. B lymphocytes (B cells) stay in the bone marrow until they are mature. Then they