Isolation and characterization of early pregnancy factor.

Early pregnancy factor (EPF) was purified from the pooled sera of 210 pregnant women at 3-8 weeks of gestation. Sera from healthy nonpregnant women were used as control. The samples (G-II, G-III and G-IV) obtained from pregnant women had EPF activity but no HCG activity. Polyacrylamide gel electrophoresis showed that the major bands in pregnant G-III and G-IV were at similar positions in tube gels. The results of SDS-PAGE showed 3 bands in pregnant G-IV: 57.0 kD, 38.0 kD and 19.0 kD. The basic active form of EPF may be a small peptide of 19.0 kD. The isoelectric points of pregnant G-IV were 6.45 and 8.20.