H2-M3 Restricted Presentation of a Listeria-derived Leader Peptide

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Abstract
Rearranged immunoglobulin variable genes are extensively mutated after stimulation of B lymphocytes by antigen. Mutations are likely generated by an error-prone DNA polymerase, and the mismatch repair pathway may process the mispairs. To examine the role of the MSH2 mismatch repair protein in hypermutation, Msh2−/− mice were immunized with oxazolone, and B cells were analyzed for mutation in their VκOx1 light chain genes. The frequency of mutation in the repair-deficient mice was similar to that in Msh2+/+ mice, showing that MSH2-dependent mismatch repair does not cause hypermutation. However, there was a striking bias for mutations to occur at germline G and C nucleotides. The results suggest that the hypermutation pathway frequently mutates G·C pairs, and a MSH2-dependent pathway preferentially corrects mismatches at G and C.