Endometriosis is a benign gynecological condition, associated with a dysfunctional immune response that facilitates progression of peritoneal lesions. Specific immune cells are hypothesized to be recruited to peritoneal endometriotic lesions; though little is known about the significance of specific T and NK cell expression and the microanatomical zoning of lesions. This study aimed to characterize the zoning of T and NK cell populations in endometriotic peritoneal lesions compared to histologically normal peritoneum.Methods and Results:
Immunohistochemical analysis of CD3+ and CD8+ T cells and CD57+ NK cells in 18 peritoneal endometrial lesions and 20 normal peritoneal biopsies revealed greatly increased expression of these immune cells in women with confirmed endometriosis. Alpha-smooth muscle actin (α-SMA) antibody was used to detect the reactive a-SMA zone surrounding the core glands and stroma. CD57+ NK cells and CD3+ and CD8+ T cells were significantly over-expressed (p<0.01) throughout the peritoneal endometriotic lesions compared to normal peritoneum (in women without endometriosis) and these cells were highly expressed in the core lesion zone compared to expression in the adjacent α-SMA zone and surrounding peritoneum.Conclusions:
Our observations support the concept that immune cell populations are recruited into developing endometriotic lesions. We have for the first time shown that NK and T immune cells are distributed differentially across various microanatomical zones of peritoneal lesions. Such understanding of zone specific immune-cell expression is crucial for better defining the roles these immune cells play in endometriotic lesion establishment and progression.