Decreased levels of the potent regulator of monocyte/macrophage activation, interleukin-13, in the peritoneal fluid of patients with endometriosis

Endometriosis is characterized by an increase in the number, activation andsecretory activity of peritoneal fluid macrophages. Factors regulating theactivation of these cells may be important in the pathophysiology of thisdisease. In this study we measured by enzyme- linked immunosorbent assaythe concentrations of the macrophage inhibitory factor interleukin (IL)-13in the peritoneal fluid of women with and without endometriosis. It wasfound that women with endometriosis had significantly lower amounts ofIL-13 (95 +/- 9.8 pg/ml) in peritoneal fluid, compared with women withoutendometriosis (115 +/- 30 pg/ml) (P < 0.01). No cycle-specific variationwas evident for either group. Another macrophage inhibitory interleukin(IL-10) was also measured, but no differences between women with (16.1 +/-13.2 pg/ml) or without (10.3 +/- 5.6 pg/ml) endometriosis were seen. Theimmunolocalization of IL-13 was assessed in eutopic and ectopic endometriumand in isolated peritoneal fluid cells. Glandular epithelial cells andstromal cells in both eutopic and ectopic endometrium were immunopositivefor IL-13. No cycle-specific differences in the immunolocalization of IL-13were seen. In conclusion, the reduced amounts of IL-13 in the peritonealfluid of women with endometriosis may lead to a lack of suppression ofmacrophage activation, thereby contributing to the overall pathogenesis ofthis disease.