Estimates put the origin of V(D)J recombination at ∼450 million years ago (for reviews, see references 1, 2). It has been speculated that it all started with a chance occurrence, the integration of a mobile element into a gene encoding an Ig domain 3. The acquisition of the V(D)J recombination system represented a major advance in the biological arms race between vertebrates and their pathogens, as the diversity created by the necessity of piecing antigen receptor genes back together again endowed the host with a new way to counter the onslaught of constantly mutating microbes. It appears that the V(D)J recombination system has, subsequent to its installation in the genome, played an integral and demonstrable role in reshaping Ig and TCR loci. Genetic repercussions in fact may continue even today.
As recently as only a few years ago,...
