Nobuhiro Kimura

The α and β Chains of the T-Cell Receptor

The mammalian immune system must be equipped to recognize and eliminate a vast number of different foreign antigens. These antigens must be distinguished from self molecules to ensure that the organism’s own structures are preserved, necessitating a well-regulated network of cells and their products. The immune system can be divided into the closely interacting compartments of nonspecific immunity and specific immunity. Nonspecific immunity is effected by cells such as macrophages and natural killer cells, which eliminate foreign antigen by lytic and digestive processes. These cells, by themselves, cannot distinguish between foreign and self antigens because they are nonspecific, and thus must be closely regulated and directed. This regulation is effected by cells from the specific immune compartment, B and T lymphocytes, which provide the fine tuning of the immune response. These two cell types are very similar in their specific recognition of antigen by means of a diverse clonally distributed repertoire, but differ in the molecules used to mediate their recognition of antigen and the context in which it is recognized. B lymphocytes secrete immunoglobulins and express them on their cell surfaces. These molecules are capable of recognizing both soluble antigen and that on the surface of cells. The portion of the molecule that is not involved in antigen recognition participates in a number of immune reactions, including those involving cells of the nonspecific compartment, that lead to the elimination of antigen (Davies and Metzger, 1983).

Genes Encoding the α-, β-, and γ-Chains of the Human T Cell Antigen Receptor

The genes of the T cell antigen receptors have been cloned. Similar to immunoglobulin genes, they consist of noncontiguous variable, diversity, and joining segments as well as one or more constant region genes. Although these genes belong to the immunoglobulin supergene family, they are distinct genes and may have evolved from a common primordial gene.