Stavnezer, JanetSchrader, Carol E.2022-08-232022-08-232014-12-012015-05-29J Immunol. 2014 Dec 1;193(11):5370-8. doi: 10.4049/jimmunol.1401849. <a href="http://dx.doi.org/10.4049/jimmunol.1401849">Link to article on publisher's site</a>0022-1767 (Linking)10.4049/jimmunol.140184925411432https://hdl.handle.net/20.500.14038/30373IgH class switching occurs rapidly after activation of mature naive B cells, resulting in a switch from expression of IgM and IgD to expression of IgG, IgE, or IgA; this switch improves the ability of Abs to remove the pathogen that induces the humoral immune response. Class switching occurs by a deletional recombination between two switch regions, each of which is associated with a H chain constant region gene. Class switch recombination (CSR) is instigated by activation-induced cytidine deaminase, which converts cytosines in switch regions to uracils. The uracils are subsequently removed by two DNA-repair pathways, resulting in mutations, single-strand DNA breaks, and the double-strand breaks required for CSR. We discuss several aspects of CSR, including how CSR is induced, CSR in B cell progenitors, the roles of transcription and chromosomal looping in CSR, and the roles of certain DNA-repair enzymes in CSR.en-USAnimalsB-LymphocytesCytidine DeaminaseDNA RepairHumans*Immunoglobulin Class SwitchingImmunoglobulin Heavy ChainsLymphocyte ActivationCellular and Molecular PhysiologyImmunityJournal Articlehttps://escholarship.umassmed.edu/faculty_pubs/6457158524faculty_pubs/645