Antifertility Effect of Progesterone Antibodies in Mice

Early embryo development and implantation were arrested in ICR mice which were passively immunized with a mouse monoclonal progesterone amtibody given as a single intraperitoneal injection at 12 hrs or 60 hrs post coitum (p. c.). Unimplanted embryos were recovered from the reproductive tract of the antibody-treated mice and none of these progressed to the blastocyst stage. The most pronounced effect was an arrest of embryonic development at a stage prior to cavitation. The plasma progesterone concentration in the blood taken by carbiac puncture increased greatly after the treatment by virtue of high affinity binding by the antibody in circulation. The result showed that passive immunization against progesterone shortly after mating interfered with early hormone dependent steps which were essential for normal embryonic development.