IMMUNOREGULATORY ACTIVITY IN ADULT-RAT TESTICULAR INTERSTITIAL FLUID - ROLES OF INTERLEUKIN-1 AND TRANSFORMING-GROWTH-FACTOR-BETA

Studies on the effect of rat testicular interstitial fluid (IF) on T-c ell function have reported both stimulatory and inhibitory actions. Sp ecific cytokines produced within the testis, particularly interleukin- 1 (IL-1) and transforming growth factor beta (TGF beta), may contribut e to these apparently conflicting observations. In proliferation assay s employing lectin- or antibody-activated thymocytes or mature T cells in vitro, adult rat testicular IF stimulated T-cell activation and/or proliferation at low assay doses and was inhibitory at higher doses. The stimulatory activity was blocked by recombinant IL-1 receptor anta gonist. The inhibitory activity was not affected by a polyspecific TGF beta antiserum. The biological characteristics of the inhibitor were distinct from those of a similar, but considerably less potent, activi ty in platelet-depleted serum. These data demonstrate that rat testicu lar IF contains biologically significant concentrations of IL-1 but ha s a predominantly inhibitory action on T-cell responses. The factor pr edominantly responsible for this inhibitory activity displays a relati vely large apparent molecular weight, is protease sensitive and partia lly heat labile, but does not appear to be one of the known mammalian TGF beta isoforms.