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

The heterophile antigens Gal alpha 1-->3Gal and N-glycolylneuraminic acid a re the major obstacle to grafting mammal organs, especially from pig, to ma n. Lack of expression of these common xenoantigens by birds has raised inte rest in ostrich as a potential organ donor for xenotransplantation. Glycosp hingolipids of ostrich liver and kidney were investigated for their carbohy drate determinants. Both organs were found similar in their glycolipid comp osition with three major species, mono-, di-, and pentaglycosylceramide. Th e pentaglycosylceramide was characterized as the Forssman antigen. In both organs, the ceramide portion was highly hydroxylated with prevalence of alp ha-hydroxylated fatty acids, C18 phytosphingosine in kidney and C18 sphingo sine in liver Forssman glycolipid, These data indicate that hydroxylation o f 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 galabio sylceramide core indicates that the Forssman tetraglycosylceramide also exi sts in vivo. Its precursors, galactosyl- and galabiosylceramide, were chara cterized in kidney and liver. The Forssman antigen is the third heterophile antigen against which man raises natural antibodies. Its localization in t he vascular endothelium and connective tissue makes ostrich an unpromising organ or cell donor for xenotransplantation to man.