Blood group A-like glycolipid and a novel Forssman antigen in the hepatocarcinoma of a blood group O individual.

Two glycolipid fractions that inhibit Blood Group A hemagglutination were isolated from hepatocarcinoma tissue of a Blood Group O individual. One fraction corresponding to a ceramide pentato hexasaccharide weakly inhibited hemagglutination caused by blood group anti-A sera and gave a precipitin reaction with Rana catesbiana lectin. The fraction had no Forssman activity, showed a single spot on thin-layer chromatography, and was degraded by hog liver a-A/-acetylgalactosaminidase to a gly colipid with a higher thin-layer chromatography mobility than that of the original glycolipid. The enzyme-treated product had no A-like activity. The direct probe mass spectrometry of the fraction after permethylation indicated the presence of the immunodominant sugar sequence GalNAc-»Hex-»HexN, but the absence of a tetrasaccharide A determinant, HexN—»[Fuc—»]Hex—»HexN, and a fucosyl residue. The other fraction corresponding to a ceramide dito trisaccharide showed only a very low A-like inhibition but showed a strong Forssman activity (inhibition of sheep erythrocyte hemolysis by anti-Forssman antibodies and complement). The activity was completely abolished by hog liver a-A/-acetylgalactosaminidase with a simultaneous elimination of thin-layer chro matography spots, one corresponding to ceramide trisaccharide and the other with slightly higher mobility. The presence of the Forssman determinant, HexN—»HexN, in this fraction was clearly indicated by direct-probe mass spectrometry with a selected ion recording during continuous-temperature-gradient evaporation. Although the supply of the tumor tissue in this case was extremely limited, the above information clearly indicates the presence of an aberrant A determinant and an unusual shortchain Forssman determinant in the hepatocarcinoma of the Blood Group O individual. The tissue did not contain normal Forssman glycolipid with a ceramide pentasaccharide struc ture.