Effects of diethylstilbestrol on human natural killer cells in vitro.

Exposure of human peripheral blood lymphocytes to diethylstilbestrol (DES) in vitro resulted in inhibition of Natural Killer (NK) cell activity. DES inhibited NK activity in a dose and time-dependent manner with maximal effect after an 18 h exposure time. Significant reduction in cytotoxicity was obtained at concentrations of DES equal to or above 1 microM. The DES-induced inhibition of NK activity was reversible and totally abrogated within 18 h of culture in the absence of DES. Studies at the single cell level revealed that DES impaired the lytic activity of NK cells without interfering with recognition of target cells. The presence of indomethacin or aspirin during exposure to DES completely reversed the DES-induced inhibition of NK activity, indicating that a product of the cyclooxygenase system mediated the suppression.