Pre-B cell receptor signaling mediates selective response to IL-7 at the pro-B to pre-B cell transition via an ERK/MAP kinase-dependent pathway

B lymphocyte development is regulated at multiple checkpoints, mediated by signals originating both inside and outside the cell. Two signaling pathway s known to be essential in this process are interleukin-7 (IL-7) and the pr e-B cell receptor (pBCR). We have shown previously that these signaling pat hways intersect functionally. Specifically, response to low concentrations of IL-7 requires pBCR expression. In this report, we identify the ERK/MAP k inase pathway as a key regulatory component of this response. We propose a molecular mechanism for the selective expansion of pBCR(+) precursors and f or the culling of inappropriately rearranged pro-B cells.