Phenotypic and functional studies of leukocytes in human endometrium and endometriosis

The aetiology of endometriosis, a common and disabling disorder, is present ly unknown, although immune dysfunction could allow ectopic endometrial fra gments to survive outside the uterine cavity, These studies investigate the relationship between leukocyte populations, steroid hormone receptor expre ssion, proliferative activity, bcl-2 expression and apoptosis in eutopic an d ectopic endometrium from women with endometriosis or adenomyosis at diffe rent phases of the menstrual cycle, Significantly increased oestrogen recep tor expression, bcl-2 expression and numbers of CD8+ leukocytes were found in ectopic compared with eutopic endometrium in endometriosis, and CD56+ en dometrial granulated lymphocytes (eGLs) were significantly reduced in ectop ic endometrium, Apoptotic cells were rarely found in control and subject en dometria, In contrast with endometriosis, adenomyotic lesions showed identi cal steroid hormone receptor expression, proliferative activity, bcl-2 expr ession and leukocyte subpopulations to eutopic endometrium, indicating diff erent aetiologies for these disorders. The unusual CD56+ CD16- eGLs present in large numbers in late secretory phase eutopic endometrium were highly p urified (>98%) by immunomagnetic separation, Except for a negligible cytoto xic activity of eGLs from early proliferative samples, cytotoxic activity o f eGLs from non-pregnant endometrium during the menstrual cycle was compara ble with those in peripheral blood, predominantly CD56+ CD16+ natural kille r cells. eGLs from non-pregnant endometrium and early pregnancy showed a va riable proliferative response to 5 and 100 U/ml interleukin-2 over 48-h and 120-h time courses. eGLs are evidently functionally important in the eutop ic endometrium. Their absence in endometriotic lesions together with increa sed CD+8 T-cell numbers and increased oestrogen receptor and bcl-2 expressi on may have significant effects on the development and progression of endom etriosis.