Monkey anti-placental serum as an abortifacient.

The abortifacient effect of antiplacental sera was confirmed with the use of goat and rabbit anti-Rhesus monkey placental globulin (IgG). To induce abortion, a total of 600-1000 mg IgG (from goats and rabbits treated to produce antiplacental sera) was injected intravenously over 3 days into 9 monkeys at 39-54 days of gestation. As a control a similar dose of normal goat globulin was injected into 3 pregnant monkeys. Abortion occurred in 7 of the monkeys injected with IgG; 2 of these abortions were after 2 injection sequences, and 1 of these 2 may have been the result of something other than an immunoreaction. Abortion occurred in none of the monkeys injected with normal goat globulin. No anaphylaxis or harmful reactions were observed in IgG-injected monkeys. In another portion of the study unabsorbed antiplacental globulin reacted with monkey serum, liver extract, and kidney extract, as well as with monkey placental extract. IgG absorbed with serum or organ extract reacted only with placental extract. No reaction was found between the absorbed antiplacental globulin and monkey placental lactogen or chorionic gonadotrophin. Cytotoxicity titers appeared to parallel the effectiveness of the IgG preparation in producing abortion. With the use of an immunofluorescent technique it appeared that the injected antibody(s) reacted with placental specific antigen localized on the trophoblast. It is thought that the reacted tissue is then destroyed with participation of complement. The abortions were apparently caused by passive immunization.