Lecture : ANTIGENS AND ANTIBODIES
2 Nov 2022
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Antigen: antigens are substances that can stimulate an immune response in the body. Most antigens are proteins, but some are carbohydrates, lipids and nucleic acids. The specificity of an antigen is due to specific areas of its molecule called determinant sites or epitopes. Histocompatibility antigens refer to the antigens present on the plasma membrane of cells of each individual of a species. These antigens are encoded by genes known as histocompatibility genes, which collectively constitute major histocompatibility complex (mhc). These are located on the short arm of chromosome 6. Mhc present on the surface of leucocytes is known as human leucocyte-associated antigens (hla). These have been studied extensively in organ transplantation. No two persons except identical twins have the same mhc proteins. There are two subclasses of mhc genes: class i and ii. Molecules are found on the surface of virtually all the cells of the body excluding rbcs.
