PERFORIN EXPRESSION IN ENDOMETRIUM DURING THE MENSTRUAL-CYCLE

Perforin is a marker of functionally active cytotoxic T lymphocytes (C TLs) and natural killer (NK) cells. We examined perforin expression in endometrium throughout the menstrual cycle. In addition, perforin exp ression was studied in endometrial leukocytes in women with anovulator y cycles with or without progesterone therapy and in postmenopausal wo men. In the endometrium, perforin-positive endometrial lymphocytes inc reased in numbers in the middle through late secretory phases. In wome n with anovulatory cycles, the proliferative endometrium, before estro gen withdrawal endometrial breakdown, contained less perforin-positive lymphocytes compared with the premenstrual endometrium of the normal menstrual cycle. The progestin-induced endometrial decidualization was accompanied by an extensive recruitment of perforin-positive cells. I n contrast, the postmenopausal atrophic endometrium showed complete ab sence of perforin-positive cells. The lymphocytes isolated from secret ory endometrium were CD3(-), CD56(+) (similar to 80%) or CD3(+), CD8() T-cell receptor (TCR)-gamma delta(-) (similar to 20%). Almost 90% +/ - 5.5 of the CD3(-), CD56(+), and up to 25% +/- 7% of CD8(+) T lymphoc ytes contained perforin. Perforin expression was further confirmed in endometrial lymphocytes by Northern blot analysis. In vitro, isolated endometrial lymphocytes exhibited NK-like cytotoxicity, After cyclic h ormone withdrawal during normal menstrual cycle, these perforin-positi ve cytotoxic cells may be involved in endometrial stromal breakdown du ring menstruation.