Pregnancy-Associated Plasma Proteins: PAPP-A and PAPP-B

Abstract

During pregnancy, it has long been known that certain proteins appear in the plasma that are apparently absent from it in the non-pregnant state. As part of a systematic attempt to detect abnormal proteins in the circulation during several disease states, our laboratory first approached a study of this question by immunological methods in the early 1960s. It was reasoned that unique proteins in the patient's plasma might evoke antibody responses in experimental animals which could be rendered apparent by absorption of the antisera with normal plasma. One of the disease states investigated was toxemia of pregnancy, but it was soon found that normal pregnancy plasma gave equivalent results. Hyperimmune antisera were prepared in rabbits by repeated immunizations with pooled third-trimester pregnancy plasma. When the antisera had achieved adequate titre, they were exhaustively absorbed with non-pregnant female and/or male plasma. Satisfactory lots of the resulting reagent reproducibly revealed up to four proteins in late pregnancy plasma or serum by various gel diffusion tests; these were designated pregnancy-associated plasma proteins, PAPP-A, -B, -C, and -D (GALL and HALBERT, 1972; LIN et al., 1973; 1974b; 1974c). These proteins were undetectable in cord sera and in non-pregnancy plasma, male or female, the latter with or without hormonal contraception.