Neutralization of primate chorionic gonadotropin activities by antisera against the subunits of human chorionic gonadotropin in radioimmunoassay and bioassay

Antisera to the subunits (a and p) of human chorionic gonadotropin (hCG) were used in radioimmunoassay (RIA) and in neutralization of biological activity measured by rat uterine weight bioassay (RUW) to test for the presence of common antigenic determinants between the subunits and chorionic gonadotropins from the human, gorilla (gCG), chimpanzee (chCG), and rhesus monkey (mCG). Urinary kaolin—acetone extracts of gCG and chCG, as well as native hCG, inhibited antibody binding of both 125I labeled hCG—a and hCG—P in their respective immunoassay systems, but mCG was ineffective in RIA for either of the hCG subunits. Although RUW responses to hCG, gCG and chCG were neutralized by varying quantities of each antiserum, neither antiserum to hCG—a nor hCG—P inhibited the biological activity of mCG. Evidence was obtained by both RIA and RUW neutralization studies for similarity of antigenic determinants in preparations of gCG, chCG and hCG and the subunits of hCG. (Endocrinology92: 705, 1973)