Reduced isotype switching in splenic B cells from mice deficient in mismatch repair enzymes
Department of Molecular Genetics and Microbiology
*Adenosine Triphosphatases; Animals; B-Lymphocytes; Base Pair Mismatch; Carrier Proteins; Cell Cycle; Cell Division; Cell Survival; Cells, Cultured; DNA Repair; *DNA Repair Enzymes; *DNA-Binding Proteins; Flow Cytometry; Immunoglobulin Class Switching; Immunoglobulin Isotypes; Mice; Neoplasm Proteins; Nuclear Proteins; Proteins; Spleen
Life Sciences | Medicine and Health Sciences | Women's Studies
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.
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Citation: J Exp Med. 1999 Aug 2;190(3):323-30.