Selective localization of interleukin-1 receptor antagonist in eutopic endometrium and endometriotic implants

OBJECTIVES: To determine whether interleukin-1 receptor antagonist (IL-1ra) expression was concordant in eutopic endometrium and endometriotic implants. DESIGN: Paired samples of endometrium and endometriotic implants from eight patients with endometriosis were used. MAIN OUTCOME MEASURES: Interleukin-1 receptor antagonist was demonstrated immunohistochemically on frozen sections of eutopic and ectopic endometria. A sandwich technique with polyclonal rabbit anti-IL-1ra antibody and an avidin-biotin reagent (Vector Laboratories, Inc. Burlingame, CA) was used. RESULTS: Seven of eight (88%) eutopic endometrial sections revealed staining of glandular epithelium with complete absence of any staining of the stromal compartment. In the counterpart sections of endometriosis, the glandular as well as the stromal compartments were negative for IL-1ra in all patients. CONCLUSION: These data suggest a differential production of the IL-1ra in eutopic endometrium and endometriotic implants. The potential clinical implications of this finding are discussed.