B cell-derived BCGF functions as autocrine growth factor(s) in normal and transformed B lymphocytes

This paper demonstrates that B cell lines, as well as normal activated B cells generate and respond to B cell-specific growth factor(s) (BCGF). BCGF derived from B cells (B-BCGF) appears to be distinct from interleukin 1, interleukin 2 (IL 2), B cell stimulatory factor, BCGF-II, interferon-gamma, or transforming growth factor. It acts on activated B cells, but not on resting G0 phase B cells to induce proliferation. B cell lines, immortalized by Epstein-Barr virus, constitutively secrete 10-fold higher level of B-BCGF compared with normal activated B cells, suggesting that an activated autocrine loop might be operating in immortalized B cells. On the basis of our observations, we postulate that B cell clonal expansion may occur, at least in part, through a B-BCGF-dependent autocrine pathway similar to IL 2 effect on T cells.