Phytohemagglutin-induced lymphocyte transformation in oral contraceptive users.

Phytohemagglutin (PHA)-induced lymphocyte transformation (PILT) was determined in 217 women taking oral contraceptives and 203 control women by means of the uptake of 3H-thymidine into DNA of lymphocytes cultured in heterologous serum. Depressed PILT responses were observed in oral contraceptive users as compared with age-matched controls, and the magnitude of depression correlated with the duration of oral contraception and was inversely related to the clinical progestagenic potency of the component steroids. An additional group of 21 women, tested within 1 year (mean 3 months) of cessation of oral contraception, showed persistent depression of PILT responses. Suppression of lymphocyte transformation in autologous as compared with homologous, normal serum suggests that serum inhibitory factors amy be important. We found no evidence for a direct suppressive in vitro effect of synthetic estrogens and gestagens. The prevalence of autoantibodies in oral contraceptive users was similar to that in control subjects.