INCREASED EXPRESSIONS OF CD69 AND HLA-DR BUT NOT OF CD25 OR CD71 ON ENDOMETRIAL T-LYMPHOCYTES OF NONPREGNANT WOMEN

To investigate lymphocyte subpopulations and the status of T-cell activation at different phases of the menstrual cycle, lymphocytes in endometrial tissue were analyzed by dual-color flow cytometry in 39 patients. Compared with peripheral blood, the lymphocytes in the endometrium had a higher CD3(-)/(CD56(+) or CD16(+)) ratio (25.2% +/- 6.8% vs 11.1% +/- 7.0%), but an inverted CD3(+)CD8(-)/CD3(+)CD8(+) ratio (0.5 vs 1.8) and a minimal amount of B cells (3.3% +/- 3.1%) TcR gamma delta(+) T cells accounted for a minor proportion (7.8% +/- 5.1%) in endometrium. The proportions of TcR alpha beta(+) (85.0% +/- 6.6%) and CD3(+)CD56(+) (7.4% +/- 4.4%) endometrial T lymphocytes were found significantly different from those in peripheral blood (89.1% +/- 5.6% and 3.8% +/- 3.4%, respectively). As the endometrium proceeded from proliferative phase to luteal phase, the proportion of CD3(+)CD8(+) T cells in peripheral blood increased from 35.6% +/- 6.9% to 41.3% +/- 8.4% and CD3(+)CD8(-) T cells decreased from 64.4% +/- 6.9% to 58.7% +/- 8.4%. The endometrial T cells expressed high levels of CD69 (84.1% +/- 18.9%) and DR (75.0% +/- 9.7%), but rarely expressed CD25 (7.0% +/- 5.4%) and CD71 (2.8% +/- 1.8%). The patterns of expression of these activation markers were similar in both proliferative and luteal phases. Our observations suggest that endometrial T lymphocytes are in a state of recent and persistent activation. Lymphocytes expressing the NK cell markers (CD56 or CD16) and CD8(+) accounted for a significant proportion, suggesting that they may play important roles in local defense.