Fig. 3

Antibody diversity comes from combination of variable and constant domain gene elements. A The B Cell locus is composed of multiple individual Variable, Diversity, and Joining gene segments which are randomly assembled into a functional gene exon through V(D)J recombination. The recombination involves the addition of random nucleotides, increasing the junctional diversity. The sites of the rearrangement form the third complementary determining region of the antibody, which dictates the antigen binding capability of the antibody (as shown in the callout image). B Transcription from intron promoters preceding switch regions allows AID to act and induce double stranded breaks. Repair by Nonhomologous end joining (NHEJ) between two broken switch regions results in class switching