Isolation and partial characterization of early pregnancy factor (EPF) from human pregnancy serum

The isolation and partial characterization of an immunosuppressive early pregnancy factor (EPF) present in the serum of pregnant women, between 3 and 8 weeks of gestation, is described. EPF was purified using ion-exchange chromatography, affinity chromatography and HPLC gel permeation techniques. A homogeneous, active fraction containing a single polypeptide of Mr 21,000 was obtained. This 21 kDa polypeptide appears to represent the major form of rosette-inhibiting active material present in maternal serum during early human gestation.