Forssman penta- and tetraglycosylceramide are xenoantigens of ostrich kidney and liver

The heterophile antigens Gal alpha 1-->3Gal and N-glycolylneuraminic acid are the major obstacle to grafting mammal organs, especially from pig, to man. Lack of expression of these common xenoantigens by birds has raised interest in ostrich as a potential organ donor for xenotransplantation. Glycosphingolipids of ostrich liver and kidney were investigated for their carbohydrate determinants. Both organs were found similar in their glycolipid composition with three major species, mono-, di-, and pentaglycosylceramide. The pentaglycosylceramide was characterized as the Forssman antigen. In both organs, the ceramide portion was highly hydroxylated with prevalence of alpha-hydroxylated fatty acids, C18 phytosphingosine in kidney and C18 sphingosine in liver Forssman glycolipid, These data indicate that hydroxylation of kidney glycosphingolipids, which is found in mammals, has been maintained since the divergence of birds from other vertebrates. Characterization of a minor glycolipid as a Forssman tetraglycosylceramide built on the galabiosylceramide core indicates that the Forssman tetraglycosylceramide also exists in vivo. Its precursors, galactosyl- and galabiosylceramide, were characterized in kidney and liver. The Forssman antigen is the third heterophile antigen against which man raises natural antibodies. Its localization in the vascular endothelium and connective tissue makes ostrich an unpromising organ or cell donor for xenotransplantation to man.