title: Class switch recombination is IgG1 specific on active and inactive IgH loci of IgG1-secreting B-cell blasts.
abstract: Mouse B lymphocytes can be activated polyclonally by bacterial lipopolysaccharide (LPS) to secrete Ig and perform Ig class switch. In the presence of the T-cell lymphokine B-cell differentiation factor, the frequency of IgG1-secreting cells is drastically enhanced. We show here that IgG1-secreting B cells isolated from such cultures have undergone a similar DNA rearrangement of the switch regions (S mu, S gamma 1) of the Ig heavy chain constant region genes C mu and C gamma 1 on both active and inactive IgH loci. This result argues against a stochastic model of class switch recombination and suggests programmed class-specific switch recombination in the case of the switch to IgG1. In accord with this notion, cells expressing IgM but not IgG on the surface have not deleted or rearranged C mu or S gamma 1 on either chromosome.
mesh_terms: D000818:Animals; D000944:Antigens, Differentiation, B-Lymphocyte; D000954:Antigens, Surface / Q000502:physiology; D001402:B-Lymphocytes / Q000502:physiology*; D005786:Gene Expression Regulation; D005796:Genes; D007127:Immunoglobulin Constant Regions / Q000235:genetics; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007142:Immunoglobulin gamma-Chains / Q000145:classification / Q000235:genetics*; D007148:Immunoglobulin mu-Chains / Q000235:genetics*; D008213:Lymphocyte Activation; D051379:Mice; D011995:Recombination, Genetic
chemical_list: D000944:Antigens, Differentiation, B-Lymphocyte; D000954:Antigens, Surface; D007127:Immunoglobulin Constant Regions; D007143:Immunoglobulin Heavy Chains; D007142:Immunoglobulin gamma-Chains; D007148:Immunoglobulin mu-Chains