Immunoreactivity of human endometrium: correlation with endometrial dating.

Human leukocyte antigen (HLA)-DR molecules of the major histocompatibility complex II, very late antigen-1 of the integrin superfamily of molecules, B72.3 (a tumor-associated glycoprotein), Ki67 (a marker of proliferation), and epithelial membrane antigen (EMA, a high molecular weight glycoprotein) were found to have distinctive localization within endometrium throughout the menstrual cycle. These molecules were localized by avidin-biotin-complex procedure in 26 endometria dated to midproliferative, late proliferative, early secretory, midsecretory, and late secretory phases of the menstrual cycle. Proliferative phase of the menstrual cycle was characterized by expression of Ki67 and HLA-DR and absence of very late antigen-1, B72.3, and EMA in endometrial glands. Secretory phase of the menstrual cycle was marked by the appearance and persistence of very late antigen-1, B72.3, and EMA in glandular epithelium. In addition, the solid compactum of the late secretory phase was marked by the development of very late antigen-1 in the predecidual cells. These findings demonstrate that the immunoreactivity of human endometrium is under the same constraints that compel the endometrium to undergo morphological changes.