[Modification of lymphoblastic transformation by estradiol, progesterone and corticosterone in vitro]

17 beta-Estradiol (E2) and progesterone were tested in vitro for their ability to act as anti-glucocorticoids in thymus and spleen cell cultures of ovariectomized female Lewis rats. Initially, the immunosuppressive effect of corticosterone was verified and both sex steroids were also found to inhibit mitogenic, antigenic and allogeneic lymphoblast transformation although at concentrations higher than those for corticosterone. The suppressive activities were stronger in thymocyte than splenocyte cultures. On the other side, E2 significantly enhanced lymphoblast transformation at concentrations of 10(-9) to 10(-7) mol per litre while progesterone had only moderately increasing effects. Combination of corticosterone with progesterone or both sex steroids resulted in significantly elevated 3Tdr incorporation of mitogen-stimulated thymocytes compared to cultures incubated with corticosterone alone while in splenocyte cultures only the mixed lymphocyte reaction showed similar effects. No synergy between E2 and progesterone in counteracting corticosterone-induced inhibition of lymphocyte proliferation has been observed. In conclusion, corticosterone, E2 and progesterone showed a dose-dependent influence on lymphoblast transformation of thymocytes and splenocytes and progesterone had opposite effects on corticosterone-induced suppression of blastogenesis in rat lymphocytes, especially in thymocytes.