Estrogen replacement therapy and the mixed lymphocyte reaction

Alterations in immune reactivity may occur in postmenopausal women during estrogen replacement therapy. Fifty-eight women were followed during 6 months of treatment with various synthetic and natural estrogens. Samples of serum showed a dose-dependent inhibitory influence on the mixed lymphocyte reaction. Mean levels of two immunosuppressive serum factors, total cortisol and pregnancy zone protein, were increased during treatment, but individual values were not correlated to depressed lymphocyte reactivity. A direct effect of estrogen on immunoreactive cells is suggested.