Immune System Genetics

B cells are created in the bone marrow. Many millions of different B cells are made, each containing a unique gene for the specific antibody that it (and all its descendants) will make. A group of B cells with all its descendants Antibodies bind to antigens on the surface of foreign substances. is called a clone. Thus, the antibody made by one B cell clone differs from that made by any other B cell clone. T cells develop along a slightly different pathway but also contain a unique protein, called the T cell receptor, which is coded for by a gene unique to that T cell clone.

Antibodies are proteins, and like all of the body's proteins, must be encoded by genes. However, the number of distinct antibodies each of us makes (many millions) is vastly greater than the total number of genes in our entire genome (30,000-70,000). How is all this diversity encoded? To understand the answer, it is helpful to look at the structure of an antibody.