Contribution of VH gene replacement to the primary B cell repertoire

V-H replacement has been proposed as one way to modify unwanted antibody specificities, but analysis of this mechanism has been limited without a dynamic cellular model. We describe a human cell line that spontaneously undergoes serial V-H gene replacement mediated by cryptic recombination signal sequences (cRSS) located near the 3' end of V-H genes. Recombination-activating gene products, RAG-1 and RAG-2, bind and cleave the cRSS to generate DNA deletion circles during the V-H replacement process. A VH replacement contribution to normal repertoire development is revealed by the identification of V-H replacement footprints in IgH sequences and double-stranded DNA breaks at V-H cRSS sites in immature B cells. Surprisingly, the residual 3' sequences of replaced V-H genes contribute charged amino acids to the CDR3 region, a hallmark of autoreactive antibodies.