REGULATION OF T-CELL MIXED LYMPHOCYTE-REACTION REACTIVITY - DEMONSTRATION OF ENHANCING AND INHIBITORY ACTIVITY IN TUMOR-BEARING HOST MACROPHAGE SUPERNATANTS

All experiments were conducted using macrophages (M.vphi.) and T [thymus-derived] cells from normal or tumor-bearing BALB/c mice (TBM). M.vphi. supernatants were added to 1-way mixed lymphocyte reactions (MLR) to examine their involvement in positive or negative immunoregulation of normal and TBM T cell alloreactivity. M.vphi. supernatant regulation was a concentration dependent phenomenon; high concentrations inhibited while low concentrations enhanced normal T cell MLR activity. Enhancing activity of low-dose M.vphi. supernatants was abrogated by heat treatment (100.degree. C for 10 min); inhibitor activity was unaffected. TBM T cells exhibited only marginal MLR activity; this hyporeactivity could not be attributed to the action of TBM M.vphi. since normal T cell activity was enhanced, not inhibited, by addition of TBM M.vphi. supernatants. Based on heat treatment and dose-response experiments, TBM M.vphi. supernatants when compared to their normal counterparts seemed to possess a greater (not lesser) ability to enhance MLR activity. As judged by 51Cr release assays and trypan blue exclusion techniques, the inhibitor failed to exhibit any cytotoxic properties, nor was it composed totally of cold thymidine as shown by extensive supernatant dialysis and competitive inhibition studies.