Interleukin-2 and ovarian hyperstimulation syndrome: a pilot study.

A prospective case-controlled study was conducted to evaluate the association between the concentrations of interleukin-2 (IL-2) in human follicular fluid obtained at the time of oocyte collection for in-vitro fertilization (IVF) and the development of ovarian hyperstimulation syndrome (OHSS). Follicular fluid was obtained at the time of oocyte collection for IVF consecutively from 40 patients at risk of developing OHSS. Among the 40 patients participating in the study, seven subsequently developed OHSS. Their follicular fluid samples, together with those of an additional seven patients matched by age who did not develop OHSS, were tested for osmolality, total protein content and IL-2 concentrations, and mean serum oestradiol concentrations at the time of human chorionic gonadotrophin (HCG) administration and the mean number of aspirated oocytes were also measured. Follicular fluid IL-2 concentrations were significantly higher (P < 0.002) in the OHSS group as compared to the control group. No significant differences were found between the two groups regarding the mean serum oestradiol concentration on the day of HCG administration, or the mean number of aspirated oocytes, follicular fluid osmolality, or total protein concentrations. This study suggests an association between follicular fluid IL-2 concentration and OHSS. IL-2 is known to cause 'vascular leak syndrome', which resembles OHSS. These observations, together with the established interaction between the immune and the reproductive systems, may suggest a pivotal role of IL-2 in the pathogenesis of OHSS.