Enhanced Expression of Resident Leukocyte Interferon γ mRNA in Endometriosis

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Abstract
Previous studies have shown that the endometrial epithelial/stromal cell proliferative activity of endometriosis is significantly less than that of normal endometrium and that the concentration of resident stromal leukocytes is significantly greater in ectopic than in eutopic endometrium. Other work has shown that interferon gamma (IFN gamma), secreted by resident leukocytes, inhibits endometrial cell proliferation in vitro. Accordingly, we hypothesized that the lower proliferative activity of endometriosis may be related to enhanced resident leukocyte IFN gamma production. This study was designed to assess whether resident leukocytes in endometriosis express IFN gamma mRNA and to compare this expression to that of normal endometrium. Biopsies of ectopic endometrium (N = 16) from women in the follicular phase and normal proliferative (N = 9) and secretory (N = 8) endometria were examined for IFN gamma expression. Using monoclonal antibodies specific for CD45 (leukocyte common antigen), CD3 (a T-cell marker) and CD11c (a macrophage marker), leukocyte types were identified immunocytochemically, followed by in situ hybridization to examine expression of IFN gamma mRNA. Results demonstrated that (1) the overall concentration of T cells and macrophages expressing IFN gamma mRNA is significantly greater in endometriosis as compared to eutopic endometrium, and (2) the percent of each leukocyte type expressing IFN gamma mRNA is greater in endometriosis than in normal endometrium. These findings support a possible paracrine role for resident leukocytes in regulating cell proliferation in endometriosis.