title: Reduced isotype switching in splenic B cells from mice deficient in mismatch repair enzymes.
abstract: Mice deficient in various mismatch repair (MMR) enzymes were examined to determine whether this repair pathway is involved in antibody class switch recombination. Splenic B cells from mice deficient in Msh2, Mlh1, Pms2, or Mlh1 and Pms2 were stimulated in culture with lipopolysaccharide (LPS) to induce immunoglobulin (Ig)G2b and IgG3, LPS and interleukin (IL)-4 to induce IgG1, or LPS, anti-delta-dextran, IL-4, IL-5, and transforming growth factor (TGF)-beta1 to induce IgA. After 4 d in culture, cells were surface stained for IgM and non-IgM isotypes and analyzed by FACS((R)). B cells from MMR-deficient mice show a 35-75% reduction in isotype switching, depending on the isotype and on the particular MMR enzyme missing. IgG2b is the most affected, reduced by 75% in Mlh1-deficient animals. The switching defect is not due to a lack of maturation of the B cells, as purified IgM(+)IgD(+) B cells show the same reduction. MMR deficiency had no effect on cell proliferation, viability, or apoptosis, as detected by [(3)H]thymidine incorporation and by propidium iodide staining. The reduction in isotype switching was demonstrated to be at the level of DNA recombination by digestion-circularization polymerase chain reaction (DC-PCR). A model of the potential role for MMR enzymes in class switch recombination is presented.
authors.affiliation: Department of Molecular Genetics and Microbiology, Program in Immunology and Virology, University of Massachusetts Medical School, Worcester 01655-0122, USA. carol.schrader@banyan.ummed.edu
authors.forename: C E
authors.initials: CE
authors.lastname: Schrader
authors.forename: W
authors.initials: W
authors.lastname: Edelmann
authors.forename: R
authors.initials: R
authors.lastname: Kucherlapati
authors.forename: J
authors.initials: J
authors.lastname: Stavnezer
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000251:Adenosine Triphosphatases; D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism*; D020137:Base Pair Mismatch / Q000276:immunology*; D002352:Carrier Proteins; D002453:Cell Cycle / Q000235:genetics / Q000276:immunology; D002455:Cell Division / Q000235:genetics / Q000276:immunology; D002470:Cell Survival / Q000235:genetics / Q000276:immunology; D002478:Cells, Cultured; D004260:DNA Repair / Q000276:immunology*; D045643:DNA Repair Enzymes; D004268:DNA-Binding Proteins; D005434:Flow Cytometry; D017578:Immunoglobulin Class Switching / Q000235:genetics*; D007132:Immunoglobulin Isotypes / Q000096:biosynthesis* / Q000235:genetics*; D051379:Mice; D000070976:Mismatch Repair Endonuclease PMS2; D000070957:MutL Protein Homolog 1; D009363:Neoplasm Proteins / Q000235:genetics / Q000276:immunology; D009687:Nuclear Proteins; D011506:Proteins / Q000235:genetics / Q000276:immunology; D013154:Spleen
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D007132:Immunoglobulin Isotypes; C501486:MLH1 protein, human; C501485:Mlh1 protein, mouse; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D011506:Proteins; D000251:Adenosine Triphosphatases; C499533:Pms2 protein, mouse; D000070976:Mismatch Repair Endonuclease PMS2; D000070957:MutL Protein Homolog 1; D045643:DNA Repair Enzymes