In vivo ablation of surface immunoglobulin on mature B cells by inducible gene targeting results in rapid cell death.

Gene targeting experiments have demonstrated that the expression of immunoglobulin heavy chain in the pre-B cell receptor (pBCR) and of heavy and light chains in the B cell antigen receptor (BCR) marks checkpoints in early B cell development that the cells have to pass to survive. To investigate whether the persistence of mature B cells in the peripheral immune system also depends on BCR expression, we have generated a transgenic mouse in which the BCR can be inducibly ablated through V region gene deletion. Ablation leads to rapid death of mature B lymphocytes, which is preceded by down-regulation of MHC antigens and up-regulation of CD95 (Fas) and can be delayed by constitutive bcl-2 expression.