Isolation of a histamine-releasing factor from two-cell human embryo

An embryo-derived histamine-releasing factor (EHRF) was identified and partially purified from media in which two-cell human embryos were cultured. The EHRF at 5 micrograms/ml was capable of inducing 22 +/- 7% release of histamine from sensitized human leukocytes, reaching a maximum of 56 +/- 4% over an EHRF concentration range of 1-30 micrograms/ml. The EHRF was not detected in media where unfertilized oocytes were cultured or in medium alone. The effect of EHRF was not due to cytotoxicity since unsensitized leukocytes were unreactive. Histamine release did not occur when the assay was performed at 4 degrees C or in presence of EDTA.