SECRETION OF BIOACTIVE INTERLEUKIN-1 BY RAT TESTICULAR MACROPHAGES IN-VITRO

The relative capacities for testicular macrophages and resident perito neal macrophages to secrete the pro-inflammatory cytokine, interleukin 1 (IL-1), in response to stimulation by bacterial lipopolysaccharide (LPS), were compared in vitro. Macrophages were isolated from adult ma le rat testicular interstitial cells or peritoneal ravage by adherence to glass coverslips or plastic culture dishes. The macrophages were i mmediately cultured, with or without a maximal dose of LPS (1 mu g/ml) , over 24 hours at 32 degrees C. Bioactive IL-1 production was measure d by a sensitive thymocyte proliferation bioassay, employing recombina nt human IL-1 beta as the reference standard. In comparison with the p eritoneal macrophages, testicular macrophages displayed only a very sm all response to LPS, producing 2.8% of the amount of IL-1 per cell sec reted by peritoneal macrophages cultured under identical conditions. P roduction of authentic IL-1 was confirmed by inhibition of the bioassa y response in the presence of human recombinant IL-1 receptor antagoni st. A small molecular mass (<10 kDa based on ultrafiltration) inhibito r of IL-1 bioactivity was also present in the medium collected from bo th cultures, but this inhibitory activity did not account for the diff erences in activity observed. In cultures of total peritoneal cells un der similar conditions, addition of testosterone (10-1,000 ng/ml) did not affect IL-1 production in response to LPS. These data indicate tha t testicular macrophages have a reduced ability to secrete bioactive I L-1, and they provide further evidence for an altered capacity for imm une responses within the testis.