Decreased expression of the decoy interleukin-1 receptor type II in human endometriosis

Many of the biological changes occurring in the endometrium during the mens trual cycle bear a striking resemblance to those associated with inflammato ry and reparative processes. Hence, it would not be surprising to find that cytokines known for their proinflammatory properties, such as interleukin- 1 (IL-l), could play a key role in the physiology of this tissue and that t heir action would be tightly controlled by local mechanisms. In the present study, immunohistochemical and Western blot analyses show that in normal w omen (n = 39), the endometrial tissue expresses, in a cycle-dependent manne r, the IL-1 receptor type II (IL-1RII), a molecule of which the only biolog ical property known to date is that of capturing IL-1, inhibiting thereby i ts binding to the functional type I IL-1 receptor. IL-RII immunostaining wa s particularly intense within the lumen of the glands and at the apical sid e of surface epithelium, Interestingly, the intensity of staining was marke dly less pronounced in the endometrium of women with endometriosis(n = 54), a disease believed to arise from the abnormal development of endometrial t issue outside the uterus, especially in the early stages of the disease (st ages I and II). This study is the first to show the local expression in end ometrial tissue of IL-1RII, a potent and specific down-regulator of IL-1 ac tion and its decreased expression in women suffering from endometriosis.