Individual and combined effects of chorionic gonadotropin (CG), estradiol, and progesterone on the production of IFNgamma and IL-4 by human peripheral blood lymphocytes was studied in vitro together with certain intracellular mechanisms underlying the hormonal effects. High CG dose (100 IU/ml) proved to significantly decrease IFNgamma level in the T cell culture supernatant, although this effect was not observed at the background of steroid hormones. In contrast, progesterone (100 ng/ml) increased IFNgamma production by activated T lymphocytes but proved inefficient in a physiological combination with CG and estradiol. IL-4 production was almost doubled by all studied hormones and their combinations, which considerably decreased the IFNgamma/IL-4 ratio in the culture. Inhibition analysis employing blockers of cAMP-dependent protein kinase (H-89) and L-type calcium channels (verapamil) as well as an antagonist of progesterone nuclear receptors (RU-486) demonstrated that the inhibitory (for IFNgamma) and stimulatory (for IL-4) effects of CG were mediated by cAMP, while the effects of steroid hormones on the production of these cytokines were realized through genomic and non-genomic mechanisms (the latter mechanisms were largely mediated by L-type calcium channel regulation). Overall, the studied reproductive hormones could efficiently regulate synthesis of the main Th1 (IFNgamma) and Th2 (IL-4) cytokines by T lymphocytes and seem to play the key role in changing the pregnancy-specific pattern of secreted cytokines.