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. Author manuscript; available in PMC: 2015 Oct 28.
Published in final edited form as: J Clin Immunol. 2003 Jul;23(4):235–246. doi: 10.1023/a:1024571714867

Fig. 2.

Fig. 2

The requirement for induction for SHM. BCR cross-linking and T cell contact through CD40:CD40L and CD86/CD80:CD28 coengagement are required for induction of SHM. AID, which is upregulated by CD40-signaling, could directly introduce mutations by DNA deamination or could edit mRNA for an exonuclease and/or endonuclease to modify the blunt DSB into the resected DSB. These are crucial to initiate DNA repair process that leads to SHM. BCR engagement upregulates translesion DNA polymerase ζ, which, together with other error-prone DNA polymerases, such as polymerase ι, is recruited to the repair pathway and inserts mutations.