T and B-cell activation by mitogenic factor generated from antigen-stimulated lymphocytes.

Guinea-pig mitogenic factor(s) were found capable of stimulating both normal T and B cells. Preliminary physicochemical characterization could not dissociate the mitogenic factors for respective cell populations. Furthermore, both immune T and B cells could produce mitogenic factors upon stimulation with antigen in contrast to some other lymphokines which are known to be produced only by immune T cells. While T-cell-derived mitogenic factor was active on both allogenic T and B cells, it was only mitogenic to syngeneic B cells and not to syngeneic T cells. B-cell-derived factor, on the other hand, could stimulate both T and B cells either of syngeneic or allogeneic origin.