Macrophage cell surface antigen

Antibodies that, by binding to the cell surface antigen, mark the tumour cell for destruction. NK cells and macrophages express cell surface receptors that bind to the antibody Fc region (Box 13.2). Thus, antibody bound to tumour antigens directs these immune elements directly to tumour surface. Antibodies also activate complement, which is capable of directly lysing tumour cells. 

In addition to antibodies, the immune system also consists of bone-marrow derived lymphocytes, or B cells, and T cells that come from the thymus gland, both of which (indirectly) produce antibodies. These cells, in turn, may be helped by helper cells (= H) and suppressed by suppressor cells (= S). Helper cells may be alarmed as to the presence of antigens by macrophages (= M) that eat the antigens and leave parts of their meal on their cell surface. 

Class 2 MHC molecules are expressed on the surface of B cells, macrophages, monocytes, various antigen-presenting cells (APCs) and certain cells of the T-cell famify. 

An APC is a cell that displays a foreign antigen complex with MHC on its cell surface. Its major responsibility is to present these foreign antigens to T cells. T cells can identify this complex using their T-cell receptors (TCRs). There are three main types of APCs dendritic cells, macrophages, and activated B cells. Dendritic cells (DCs) are present in tissues that... 

In addition to its effects on haematopoietic cells, GM-CSF can also affect the function of mature cells. GM-CSF treatment increases the survival, cytotoxicity and eicosanoid formation by eosinophils, and can increase the tu-mouricidal activity, cytokine expression, surface antigen expression and oxidative metabolism of macrophages. It is chemotactic for endothelial cells, can induce the proliferation of some tumour cells, stimulates histamine release from basophils and affects the viability and function of Langerhans cells. Its effects on mature neutrophils are described in 7.2.1, 7.3.4. 

IgG or IgM antibodies direct the immune response toward the antigen located on a cell (e.g., a red blood cell or thrombocyte). Macrophages, NK cells, and neutrophils are recruited by the antibodies to the site of the antigen on the cell surface and destroy the cell by phagocytosis or lysis. Additionally, complement activation will damage the cell (Fig. 6.32). The result, for example, where red cells are the targets is hemolytic anemia. 

There are three different kinds of lymphocytes that have specific functions T cells, B cells and NK cells. T cells develop in the thymus while B cells develop in the adult bone marrow. The thymus and the bone marrow are the primary lymphoid organs where lymphocytes acquire specific cell surface receptors that give them the ability to recognize antigens. NK cells are cytotoxic lymphocytes that develop in the bone marrow. The phagocytes are made up of either monocytes (macrophages) or polymorphonuclear granulocytes, which include neutrophils, eosinophils and basophils. 

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