Role of reproductive hormones in control of apoptosis of T-lymphocytes

Effects of chorionic gonadotropin (CG), estradiol, progesterone, and their physiological combinations on apoptosis of human peripheral blood T-lymphocytes were studied. Neither the hormones separately nor their combinations affected the spontaneous apoptosis of T-cells. On stimulation with mitogens, a high dose of CG (100 IU/ml) significantly increased apoptosis of T-lymphocytes, but its combination with steroid hormones specific for trimester I of pregnancy decreased this parameter. Apoptosis of T-lymphocytes induced by neutrophils in mixed culture was also inhibited by the hormone combination corresponding to trimester I. In greater detail, this hormonal combination was shown to display differential effects on different T-cell subpopulations: it stimulated apoptosis of CD8⁺-lymphocytes (which seemed to be provided by CG) and inhibited apoptosis of CD4⁺-cells. Apoptosis of T-lymphocytes induced by anti-CD95 was suppressed by a high dose of progesterone (100 ng/ml) and also by its combination with CG and estradiol specific for trimester III of pregnancy. Thus, the reproductive hormones studied effectively regulated apoptosis of peripheral blood T-lymphocytes. The effect of the hormones depended on the cell type and their activation and seemed to be an important mechanism of hormonal control of immune reactions in pregnancy.