Abstract: Early pregnancy factor (EPF) was first found in the serum of pregnant rats, is one kind pregnancy-associated protein which exists in the pregnancy mammal blood serum and has immunosuppressive and growth regulation effect. The EPF amino acid sequence including 102 amino acid residues, with the chaperonin l0 homology, is the extracellular effects of Cpn10, which temperature and pH value tolerance is strong, and don’t has animals and species-specific. Its biology characteristic mainly manifests in the suppression immunity and the growth adjusts. Firstly, EPF can inhibit the mother’s immune response to prevent sperm, embryos from immune rejection, and is also the most early confirms one of pregnancy biochemistry symbols at present. Secondly, EPF can promote tumor cell growth as well as promote burns, ulcers, such as wound healing. Since the EPF can enhance anti-lymphocyte serum inhibited T cell rosette formation, therefore, the rosette inhibition test is the classic method of detecting EPF activity. EPF can be used in animal reproduction domain to diagnose animal’s early time, super early pregnancy, pregnancy interrupt examination, the survival state after embryo transfer, has an important value in the evaluation of male fertility and reproduction and the treatment of diseases.

Key words: early pregnancy factor; chaperonin 10; rosette inhibition test