Chapter 2 The B-cell in immunity

B cells, the source of all antibody molecules in the immune system, are produced throughout life from stem cells in the bone marrow in an ordered process which maximizes diversity and deletes self-reactivity. In the periphery B cells are available to respond to foreign antigen. For antigens which require T cell help, the B cell response not only produces antibody which helps in the clearance of the antigen, but also generates long lived memory cells which can respond to the same antigen years later. These memory B cells also have antibody molecules whose fit for the antigen has been improved during the response by the process of affinity maturation, carried out in a special structure called a germinal center. A number of immunodeficiencies have been defined in which specific stages of B cell development or function are affected. For some of these, the exact nature of the mutation is now known, raising the possibility of gene therapy at some time in the future.