A previous study of human chorionic gonadotropin (HCG) demonstrated 2 antigens, Ag 5 and Ag 6, characteristic of pregnancy and distinct from the biologically active hormone. In this study urine extracts prepared from male and female patients with trophoblastic proliferative disorders were tested for the presence of antigens Ag 5 and Ag 6. It has been possible to subdivide urine extracts containing biologically active HCG into 3 immunologic groups. Urine extracts which contain both antigen Ag 5 and Ag 6 were obtained from 5 of 6 patients with gestational choriocarcinoma, 6 of 9 patients with hydatidiform mole and 1 of 4 male patients with germinal tumor. A second group consisting of urine extracts obtained from 1 of 6 patients with gestational choriocarcinoma and 3 of 9 patients with hydatidiform mole did not contain detectable amounts of either antigen Ag 5 or Ag 6. However, a third antigen (designated as antigen Ag 5A) which cross-reacts with HCG antiserum was demonstrated. Urine extracts obtained from 3 of 4 male patients with germinal tumor did not contain detectable amounts of antigen Ag 5, Ag 6, or Ag 5A. This report is concerned with the immunologic and biologic characteristics of urine extracts prepared from patients with trophoblastic proliferative disorders. It is proposed that immunologic testing in trophoblastic proliferative disorders offers a new index in the study of trophoblastic biology.

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