Pursuing the identity of Super-early pregnancy factor

In 1974, Morton et al. found that substance(s) included in the pregnancy mouse serum inhibited the rosette formation and named it “early pregnancy factor(EPF)”. Such inhibition is thought to be caused by an immunosuppressive property of EPF, and investigation of this factor could be the key to interpreting the immunological relationship between mother and fetus during pregnancy. From our extensive studies of EPF, we have defined Super-EPF as that detected in the mammalian pregnancy serum and EPF-like substance(s) as those detected in other materials. Even 35 years have passed since the discovery of EPF, little is known about this substance. In this review, we mainly describe our data obtained from purification for determine the structure of bovine Super-EPF and EPF-like substance(s). We also discuss the characteristics and potential of SuperEPF based on our findings.