Implantation: Stimulation of human endometrial epithelial cell interleukin 6 production by interleukin 1 and placental protein 14

The effect of interleukin 1 (ILI) and placental protein 14 (PP14)on the production of interleukin 6 (IL6) by cultured human endometrialepithelial cells prepared from endometrial biopsy material obtainedat different stages in the menstrual cycle was investigated.Basal IL6 production by cells prepared from proliferative endometriumwas greater than that produced by cells prepared from secretoryendometrium (7.3 ± 0.3 and 1.1 ± 0.2ng/well/24h respectively, P < 0.001). IL1 (0.025–2.5 ng/ml) causeda dose-dependent increase in IL6 production by cells preparedfrom both proliferative and secretory endometrium, but cellsprepared from secretory endometrium responded to a lower concentrationof ILI than those prepared from proliferative endometrium. ILI-stimulatedIL6 production by epithelial cells prepared from secretory endometriumtypically reached 10 times basal values, while in cells preparedfrom proliferative endometrium stimulated levels were approximatelytwice the basal values. PP14 (1–50 µg/ml) also causeda dose-dependent increase in IL6 production by epithelial cellsprepared from secretory endometrium, but had no effect on IL6production by cells prepared from proliferative endometrium.Even in secretory cells PP14 was less effective than IL1 atstimulating IL6 production, with stimulated levels only reachingtwice the basal values. This suggests that PP14 and IL1 actvia different mechanisms in the stimulation of IL6 production.The results show that IL6 production by human endometrial epithelialcells is stimulated by other immunomodulatory peptides and thismay be part of the network of such peptides in the endometriumwhich may influence embryo implantation.