Basic components of the immune system part 23

The genes for T cell receptor chains are on different chromosomes with the β and α molecules on chromosome 7, while α and δ are on chromosome 14. The four chains are made up of a variable region and a constant region similar to those observed with the immunoglobulins. The variable regions are also numerous and joined at D and J regions by RAG1 and RAG2. This permits  a diversity of antigen recognition similar to that observed with immunoglobulin, but additional somatic mutation is not involved in T cells.These similarities have led to the concept that genes for antigen-specific  T cells evolved in the same manner as immunoglobulin from a parent, gene, and both are members of superantigen family.