Effect of hormone replacement therapy on post-menopausal changes of lymphocytes and T cell subsets.

Immunosenescence is associated with the occurrence of lethal diseases, such as infection and malignancy. Since endocrinosenescence occurs simultaneously with immunosenescence, we determined whether or not lymphocytes and T cell subsets were altered in post-menopausal women. The ability of hormone replacement therapy (HRT) to reverse or modify the aberrations of the cell populations observed in elderly women was also examined. Thirty-nine untreated post-menopausal women and 39 women on HRT were studied. The proportions of lymphocytes and T cell subsets (helper, cytotoxic and immature T cells, and naive and memory/activated T cells) were determined by two color flow cytometry. Thirteen women were examined before and during HRT. At late post-menopause (> or = 30 years post-menopausal period), the proportion of peripheral blood lymphocytes showed a tendency to decline (p=0.06) compared with that at early (< or = 10 years) post-menopause. Significant (p<0.05) decrease in naive T cells and an increase in memory/activated T cells occurred at late post-menopause compared to those at early post-menopause. The percentage of lymphocytes in women on HRT was significantly (p<0.05) higher than that in untreated women at late post-menopausal stage. Furthermore, in a prospective study, HRT induced a significant (p<0.02) increase in the percentage of lymphocytes but showed no effect on the aberrations of naive and memory/activated T cells. HRT prevents the decline in the lymphocytes observed in post-menopausal women. However, HRT appears not to influence the observed alteration in T cell subsets.