Evolution of antibody and T-cell receptor V genes--the antibody repertoire might have evolved abruptly.

Structural homology present between antibody genes and T-cell antigen receptor (TCR) genes include not only V genes but also D and J segments. This may indicate that the gene duplication occurred involving a large chromosomal region containing all these genes and segments. It is conceivable, however, that the TCR gene complex is the ancestor, as effective selective forces to diversity V gene sequences are provided by MHC polymorphism only for TCR V genes. Consequently, we argue that the antibody repertoire may have emerged rather abruptly in evolution.