Oestrogen as an inhibitor of human NK cell cytolysis.

Natural killer (NK) cells are large granular lymphocytes attributed with the ability to lyse certain tumour cells. Previous studies on NK cells have demonstrated only an in vivo suppression of NK cell activity by 17 beta-oestradiol. The suppressive action of oestrogen on other peroxidase-containing leukocytes by virtue of its redox potential has already been documented. In the present study oestrogen suppressed NK cell cytolysis in vitro (determined by the release of [51Cr]chromate from radiolabelled cells) in a dose-dependent manner (p less than 0.01). Parallel experiments demonstrated a similar reduction in NK cell luminol chemiluminescence during activation by K562 tumour cells. Therefore, it would appear that there may be an association between NK cell lysis and their peroxidase/oxygenase activity.