Molecular Properties of F9 Embryoglycan Recognized by a Unique Antibody in Sera from Patients with Germ Cell Tumors¹

Human antibody against an embryoglycan present on a mouse teratocarcinoma cell line F9 was found in sera from 16 of 29 patients with embryonal carcinoma, yolk sac tumor, immature teratoma, and choriocarcinoma of gonadal and extragonadal origins by Farr assay. In contrast, none of the sera from patients (77 cases) with dysgerminoma, seminoma, germinoma, and mature teratoma or from patients (118 cases) with nongerm cell types of ovarian tumors contained this antibody. The antigenic embryoglycan was of high molecular weight (M_r >70,000) on Sephacryl S300 column chromatography and carried binding sites for Grifonia simplicifolia agglutinin-1. The antigenic embryoglycan was also found in F9 cell-cultured medium. Absorption of patients' sera with synthetic Blood Group B trisaccharides failed to remove the antibody against F9 embryoglycan. None of these patients' sera showed higher hemagglutination titer to rabbit erythrocytes than the normal range. In contrast, α-galactosyl carbohydrates obtained from Ehrlich ascites tumor cells effectively inhibited the binding of patients' sera with F9 embryoglycan. These results indicate that the human antibody against F9 embryoglycan recognizes α-galactosyl structures that are distinct from B blood group antigen, but are cross-reactive with α-galactosyl structures on Ehrlich ascites cells.