title: IgH chain class switch recombination: mechanism and regulation.
abstract: IgH 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.
authors.affiliation: Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, MA 01605 janet.stavnezer@umassmed.edu.
authors.forename: Janet
authors.initials: J
authors.lastname: Stavnezer
authors.affiliation: Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, MA 01605.
authors.forename: Carol E
authors.initials: CE
authors.lastname: Schrader
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000502:physiology*; D003564:Cytidine Deaminase / Q000378:metabolism*; D004260:DNA Repair; D006801:Humans; D017578:Immunoglobulin Class Switching; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D008213:Lymphocyte Activation; D000098830:AICDA (Activation-Induced Cytidine Deaminase)
chemical_list: D007143:Immunoglobulin Heavy Chains; D000098830:AICDA (Activation-Induced Cytidine Deaminase); D003564:Cytidine Deaminase