Antibody diversification mechanisms. In addition to the combinatorial diversity of variable (diversity) joining [V(D)J] segments and heavy/light chains, antibodies are diversified by different mechanisms, including gene conversion, somatic hypermutation, and class switch recombination. The main enzymes implicated in each process are shown in orange. Animal names represent species in which a mechanism has been experimentally demonstrated. Abbreviations: AID, activation-induced cytidine deaminase; GALT, gut-associated lymphoid tissue.