Complex layers of genetic alteration in the generation of antibody diversity

The diversity of the immune system is known to be somatically amplified by various genetic alteration mechanisms including V(D)J recombination, somatic hypermutation (SH) and class switch recombination (CSR). Recent findings that both CSR and SH are abolished by mutations of mouse and human AID, a member of the RNA-editing cytidine deaminase family, suggest that at least dual layers of genetic alteration mechanisms are involved in the generation of immune diversity.