EVOLUTION OF VERTEBRATE ANTIBODY GENES

The antibody genes are likely to have evolved from the T cell antigen receptor genes (TcR). As the diversification of the TcR variable region genes occurred during the coevolution with MHC molecules, the antibody repertoire might have emerged abruptly using the pre-existing TcR repertoire. The increased risks of infections through injuries in digestive organs (e.g. intestine) of gnathostomes may have been one driving force for the evolution of antibody genes. Once many antibody germ-line genes had evolved, homogenisation mechanisms by non-reciprocal genetic processes could have maintained their genetic diversity and integrity. It is argued that as the antibody VH gene family is stable for as long as 150 to 200 million years of evolution, the V gene family reflects such processes. The redundancy and similarities of antigen binding specificities and sequences of a V gene family may serve to protect against disruptive processes in evolution and ontogeny.