Role of monocytes in the augmentation of human natural killer cell activity by interleukin-2

The cellular requirement(s) and mechanism(s) involved in the augmentation of human natural killer cell (NK) activity by Interleukin (IL-2) were studied. NK activity was enhanced by IL-2 in the absence of monocytes. This potentiation of IL-2 on NK enhancement was suppressed by PGE2, and was enhanced by indomethacin in the experiments using unfractionated mononuclear cells. When monocyte-depleted cells were stimulated with IL-2, the cytotoxic activity was greater than that seen with unfractionated mononuclear cells. Monocytes in culture produced PGE2 which partially reduced NK enhancement by IL-2. These findings suggest that PGE2, produced by monocytes, regulates the NK enhancement by IL-2 in vitro.