Studies on the immunosuppressive properties of 7,25-dihydroxycholesterol--I. Reduction of interleukin production by treated lymphocytes.

Several oxysterols are powerful immunosuppressors. Among them 7,25-dihydroxycholesterol (7,25-OHC) seems to be particularly interesting. The effect of this synthetic sterol on murine lymphocytes, stimulated by Con A, or by allogeneic or TNP-modified syngeneic lymphocytes, was investigated. The results showed that the induction of cytotoxic T-lymphocytes (CTL) was strongly inhibited by a treatment with non-toxic concentrations of this sterol. A marked reduction of interleukin 2 (IL-2) production by alloantigen stimulated lymphocytes occurred at the same concentrations. We also showed that receptors to IL-2 did not appear on lymphocytes stimulated by Con A, when 7,25-OHC was added at the beginning of the culture. The addition of exogenous IL-2 to the culture was found to only slightly reverse the inhibition caused by 7,25-OHC. Taken together, these results indicate that an impairment at the early steps of lymphocyte activation, involving IL-2 secretion, could be responsible, at least in part for the various immunosuppressive effects of 7,25-OHC.