ENHANCING EFFECT OF 17-BETA-ESTRADIOL ON HUMAN NK CELL-ACTIVITY

The in vitro effect of 17beta-estradiol on NK activity was studied. Th e proliferation and NK activity of YT-N17 (a human NK-like cell line) were enhanced by 17beta-estradiol (E2), and the enhancement was blocke d by tamoxifen (Tx), an antagonist of E2. On the contrary, other stero id hormones such as Tx, progesterone. and testosterone had no effect. YT-N17 contained 11.8 fmol/mg protein of estrogen receptor (mean of tw o independent assays), a value which was 5-10-fold higher than that of other hematopoietic cell lines. An enhancement of NK activity by E2 w as also seen in large granular lymphocytes obtained from normal subjec ts, and it was again suppressed by Tx. These data suggest that E2 is o ne of the activating factors for NK/LGL cells.