To investigate whether Rad54/Rad54B-mediated HR is involved in SHM, we determined the ratio of mutated versus non-mutated Vlambda PCR products from memory (IgM-, IgD-, Vlambda1+) and GC (PNA(high), Vlambda1+) B cells, the mutation load, the mutation frequency, the base exchange pattern and the distribution of somatic mutations along the rearranged Vlambda light chain (VlambdaLC) genes. 