The human T cell receptor for antigen: structure, ontogeny and gene expression.

T cell receptor molecules are now well characterized as well as the genes encoding alpha and beta chains of this molecular complex. The genome organisation of alpha and beta chain genes is similar to the genomic organisation of immunoglobulin genes. In T cell differentiation immature precursor cells move into the human thymus, where they mature and subsequently are released into the periphery as immuno-competent T cells with a variety of different functions. The processes at work in thymic ontogeny are understood, only in part, and await further study. One aspect of T cell differentiation is the acquisition of immunocompetence by T cells in thymic ontogeny. This process is associated with T cell receptor gene rearrangements and T cell receptor gene expression. The mechanisms leading to gene expression have been studied in many systems and basic principles are now emerging. The enzyme RNA polymerase II, which synthesizes m-RNA requires additional factors for its activity, and these factors have, at least in part, been identified as proteins. Experiments aimed at identifying DNA-protein interactions at the V beta upstream regulatory region are discussed.