A factor secreted by human embryo stimulates cytokine release by uterine mast cell

The existence of a biochemical network of embryo-maternal communicationimplies that various secreted molecules constitute a signal-responsemechanism, important for the process of embryo implantationin mammals. Here we report the purification of a protein withan apparent molecular weight of 136 kDa, responsible for a 2000-foldincrease in embryo-derived histamine-releasing factor (EHRF)activity. This protein, purified from medium from the in-vitroculture of 2–8-cell human embryos, by means of affinitychromatography, was capable of binding immunoglobulin (lg)Eas demonstrated by immunoblotting and enzyme-linked immunosorbentassays. We found that EHRF was capable of inducing release ofhistamine and cytokines in vitro from rat uterine tissue, collectedon day 4 of pregnancy (preimplantation stage of embryo development).When EHRF was used as a secretagogue, granulocyte macrophage-colonystimulating factor (GM-CSF) release increased from 3 to 55 pg/g(P <0.01) and tumour necrosis factor-