Detection of interleukin-6 in human follicular fluid

OBJECTIVE: To determine if interleukin-6 (IL-6) is a normal constituent of human follicular fluid (FF) after ovarian hyperstimulation and to assess whether IL-6 levels differ in conditions associated with immunological causes of infertility. DESIGN: After ovarian hyperstimulation for an in vitro fertilization (IVF) treatment cycle, FF samples were obtained at the time of oocyte retrieval. SETTING: Referral center at a tertiary care hospital. PATIENTS: Thirty women referred for IVF, including 10 patients with significant titers (greater than 40%) of antisperm antibodies and 10 with pelvic endometriosis. Ten patients with tubal infertility without antisperm antibodies or endometriosis served as controls. MAIN OUTCOME MEASURES: Analysis of FF levels for IL-6 using both bioassay and immunoassay. RESULTS: Bioactive (range 0.32 to 32.2 U/mL) and immunoreactive (range 0.34 to 13.6 ng/mL) IL-6 levels were detected in FF of all subjects after ovarian hyperstimulation. Follicular fluid IL-6 levels were substantially higher (3 to 30-fold) than that reported in serum. There was no difference in the mean concentrations of IL-6 levels between patients with antisperm antibodies, endometriosis, or tubal infertility. CONCLUSIONS: Bioactive and immunoreactive IL-6 are present in human FF after ovarian hyperstimulation, supporting a potential autocrine or paracrine role within the follicular microenvironment.