Characterization of the in vivo and in vitro effects of indomethacin on human natural killer cell activity.

The in vivo and in vitro effects of indomethacin on the natural killer (NK) cell activity against K 562 target cells were studied. In vivo administration of indomethacin, 3 X 50 mg for 7 days to normal donors did not influence baseline NK cell activity, which means that treatment with prostaglandin (PG) inhibitors can be allowed in studies on NK cell activity of persons with normal PG production. The NK cell activity of fresh mononuclear cells was boosted with pharmacological concentrations of indomethacin in vitro, while frozen cells were not. Our results indicate that indomethacin enhances the NK cell activity in vitro by blocking the prostaglandin production of monocytes, since monocyte depleted effector cells were not boosted by indomethacin.