Immunosuppression by human seminal plasma as evaluated by effect on natural killer cell cytotoxicity

Re-examination of earlier observations of the suppressive role of oxidized polyamines and their cytotoxic products, has suggested that immunosuppression by seminal plasma (SePl) observed in in vitro assays employing culture medium supplemented with serum containing amine oxidase is 'artefactual'. Investigation of the relevancy of this suggestion to immunosuppression of natural killer (NK) cell activity by SePl as related to NK cell viability was made. NK cells in various culture regimens were preincubated in SePl and medium supplemented with 10 per cent foetal bovine serum, a source of amine oxidase, without and with 0.2 mM hydroxylamine, an amine oxidase inhibitor, and 10 per cent normal human AB serum, virtually devoid of amine oxidase, and examined for viability up to 72 h by trypan blue dye exclusion and lytic activity in a 4 h 51chromium-release microcytotoxicity assay. Viability to NK cells varied with the concentration of SePl, culture medium and time of incubation. At 18 and 24 h, times corresponding to preincubation and completion of the NK cell assay, viability was greater than or equal to 75 per cent for the optimum inhibitory concentration of SePl, irrespective of the culture medium. Comparison of the lytic activity of NK cells preincubated with the optimum inhibitory concentration of SePl in the various culture regimens did not disclose significant (P less than 0.05) differences.(ABSTRACT TRUNCATED AT 250 WORDS)