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One-way mixed lymphocyte reactions (MLR) were used to establish a correlation between loss of in vitro T cell reactivity and in vivo tumor growth. Though supernatants from anti-Thy 1 treated macrophages (M phi) greatly enhanced MLR activity in normal T cells, such addition had little effect in reversing the inability of T cells from 2-week palpable tumor-bearing mice (TBM) to recognize in vitro foreign histocompatibility antigens. Since normal T cells, exposed to TBM M phi supernatants, exhibited no decrease in proliferative response, TBM T cell loss of MLR reactivity could not be ascribed to tumor-induced suppressor M phi.

Normal BALB/c mice were assessed for 2,4-dinitrofluorobenzene (DNFB)-induced contact sensitivity following adoptive transfer of macrophages (Mo). T cells, or their derived products, from normal or tumor-bearing hosts (TBH). Contact sensitivity (CS) was measured by a quantitative radioisotopic ear assay, a total in vivo system based on localization of IP-injected iodinated human serum albumin [( 125I]HSA) in the DNFB-challenged ear. Adoptive transfer of low or high doses of TBH T cells or their derived supernatants into normal recipients suppressed their responsiveness, while Mo supernatants enhanced it. Moreover, in all cases adoptive transfer of TBH cells or supernatants resulted in a lower CS response than did their normal counterparts. These results further corroborate our previous in vitro data indicating that T cells, or Mo and T cell soluble products, possess immunoregulatory capabilities in vivo.