Leukaemia inhibitory factor expression in human follicular fluid.

Leukaemia inhibitory factor expression in human follicular fluid Dear Sir, We were interested to read the paper by Arici et al. (1997) who found leukaemia inhibitory factor (LIF) expression in human follicular fluid (hFF). We would like to confirm this fact and make some short comments. Since we have postulated that LIF could play a role in the inflammatory-like processes involved in the periovulatory events, we have performed a study to assess its presence in hFF and evaluate this cytokine as a marker of oocyte quality. The preliminary results of this study were presented at the 13th Annual Meeting of the European Society for Human Reproduction and Embryology (ESHRE) (Jean et al., 1997). Briefly, the hFF samples evaluated in our study (n ϭ 96) were obtained from individual follicles at the time of oocyte retrieval for patients undergoing in-vitro fertilization (IVF). The aspirated follicles were immediately examined for the presence of oocytes and hFF were then classified into two groups based on the morphology of the oocyte. Group 1 (n ϭ 70) included hFF corresponding to oocytes that could be inseminated, while group 2 (n ϭ 26) was composed of hFF containing atretic oocytes. The LIF concentration of each hFF sample was determined in both groups by an enzyme-linked immunosorbent assay (ELISA) method (kit Medgenix, Fleurus, Belgium) while the patient serum served as a negative control for LIF detection. The sensitivity (20 pg/ml), the precision (intra-assay variation Ͻ5%), and the reproducibility (inter-assay variation Ͻ10%) of this ELISA have been reported previously (De Groote et al., 1994) while a good correlation (r ϭ 0.96; P Ͻ0.0001) between LIF measurements in several biological fluids using this ELISA and the corresponding DA-1a bioassay has been demonstrated previously (Godard et al., 1993; De Groote et al., 1994). As reported by Arici et al., we confirm that LIF was expressed in hFF samples 35 h after administration of human chorionic gonadotrophin (HCG). However, despite the lack of available data in the literature, we were astonished by the very low mean concentration of LIF measured by these authors (13.0 Ϯ 1.1 pg/ml) in comparison with the LIF concentrations reported in our study (group 1: 2833.37 Ϯ 1270.08 pg/ml and group 2: 1602.33 Ϯ 1159.01 pg/ml). In addition, the mean concentration of LIF in the pre-HCG hFF samples (0.8 Ϯ 0.3 pg/ml) appears to be very low, especially with respect to the sensitivity for LIF (2 pg/ml) …