Effect of sex hormones on human T cell activation by concanavalin A

The effect of sex hormones on concanavalin A (Con A)-activated human T cells was studied. We show that neither 17β-estradiol (E₂) nor progesterone, in concentrations of up to 10^-6 M, alters the proliferative response of peripheral-blood mononuclear cells (PBMC) of healthy postmenopausal women. Furthermore, the hormones had no effect on the composition of T cell populations and on the expression of activation markers. We extended our study to a unique T cell population that is characterized by the ability to form rosettes with human erythrocytes, following Con A activation (designated autorosette-forming cells; ARFC) and known to manifest suppressive activity. Indeed, the in vitro addition of E₂ (neither progesterone nor testosterone) to Con A-stimulated PBMC brought about 2- to 4-fold increase in the frequency of ARFC. Tamoxifen, an antiestrogen drug, reduced the frequency of estrogen-stimulated ARFC to the original low level. Furthermore, the inhibitory effect of growth medium from ARFC cultures originally stimulated with Con A + E₂ was found to be higher than that of ARFC cultures originally stimulated with Con A alone.