Suppression of T-cell mediated lymphokine production but not cytotoxic activity by macrophages

We directly compared the effects of macrophages from infiltrating MSV-induced regressing tumors (T-macrophage) or from the peritoneal cavity of mice previously injected with light mineral oil (LMO-macrophage on two functions of alloimmune spleen cells (ISC), the cytotoxic activity and production of a lymphokine, macrophage inhibitory factor (MIF). Addition of T-macrophage or LMO-macrophage to ISC did not inhibit their cytotoxicity. In contrast T-macrophage, but not LMO-macrophage, mixed with ISC inhibited their ability to produce MIF. We propose that the differential sensitivity of the two immune functions to the macrophage-dependent suppressor activity is due to the ability of macrophage to inhibit lymphocyte protein synthesis, with MIF production, but not T-cell killing, requiring active protein synthesis.