title: Homologous chromosome recombination generating immunoglobulin allotype and isotype switch variants.
abstract: We investigated whether spontaneous isotype switching in monoclonal antibody-producing hybridomas always occurs with genes on the same chromosome. Spleen cells of (BAB/ 25 X AKR/J) F1 mice, immunized with dansyl-keyhole limpet hemocyanin (DNS-KLH), were hybridized with NS-1 to generate hybridomas producing monoclonal anti-DNS antibodies of either the b or d haplotype of the BAB/25 or AKR/J parent, respectively. We selected isotype switch variants of such hybridomas using the fluorescence-activated cell sorter (FACS). Although in most cases the allotypic haplotype expressed by the parent and switch-variant hybridomas are the same, in one family of variants we noted a switch in haplotype along with the switch in isotype. This was noted in the selection of IgG2a switch variants from an IgG1 switch variant originally derived from an IgG3-producing parent. Biochemical and molecular studies confirm that the allotype switch variant expresses the same heavy-chain variable region gene complex as its parent hybridomas. As such, the allotype switch represents an example of spontaneous mitotic recombination between immunoglobulin heavy-chain genes, generating a single actively transcribed gene from loci previously positioned on different chromosomes.
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D001483:Base Sequence; D002460:Cell Line; D004247:DNA / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D005455:Fluorescent Antibody Technique; D008040:Genetic Linkage; D014644:Genetic Variation; D007126:Immunoglobulin Allotypes / Q000235:genetics*; D007136:Immunoglobulins / Q000235:genetics*; D008099:Liver / Q000276:immunology; D051379:Mice; D008815:Mice, Inbred Strains; D011863:Radioimmunoassay; D011995:Recombination, Genetic
chemical_list: D000911:Antibodies, Monoclonal; D007126:Immunoglobulin Allotypes; D007136:Immunoglobulins; D004247:DNA