Evidence for two distinct classes of murine B cell growth factors with activities in different functional assays.

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Abstract
Several previously described B cell growth factor (BCGF) activities from a number of mouse monoclonal T cell sources were compared in different functional assays. There are apparently 2 distinct classes of BCGF defined by functional actiivty and source. BCGF I, whose prototype is (EL4)BCGF, synergized with anti-Ig in the proliferation of normal splenic B cells but had no activity when dextran sulfate (DXS), rather than anti-Ig, was used to costimulate the same source of B cells. BCGF I also failed to directly stimulate BCL1 tumor B cells. BCGF II, whose prototype is (DL)BCGF, showed a reciprocal pattern of activity. BCGF II failed to synergize with anti-Ig-costimulated normal B cells to give good proliferative respones. Sources of BCGF II also directly stimulated (no anti-Ig or DXS added) B cells of the BCL1 tumor-carrying mice. The 2 BCGF may have activity on 2 substs of B cells that respond differently to induction with the 2 polyclonal B cell activators, anti-Ig and DXS. The possibilities that these different patterns of response occur in separate lineages of B cells and/or in B cells in different states of differentiation is discussed.