BIOCHEMICAL-CHARACTERIZATION OF THE FELINE AB BLOOD-GROUP SYSTEM

The biochemical nature of the feline AB blood group system was charact erized by analysing red blood cells from homozygous (genotype A/A) and heterozygous (A/B) type A, type B (B/B), and type AB cats. High perfo rmance thin layer chromatography (HPTLC) of red cell glycolipids revea led that specific neuraminic acids (NA) on gangliosides, containing ce ramide dihexoside (CDH) as a backbone, correlated with the feline AB b lood group antigens. Although disialogangliosides predominated, mono- and trisialogangliosides were also isolated. B cats expressed solely N -acetyl-NA (NeuNAc) on these gangliosides. In addition to expressing N -glycolyl-NA (NeuNGc) containing gangliosides, A red cells have gangli osides with only NeuNAc or mixtures of both NA. HPTLC profiles of disi alogangliosides from homozygous and heterozygous A cats differed sligh tly in the quantity of disialogangliosides. Equal amounts of NeuNAc an d NeuNGc containing disialogangliosides, as well as two intermediary f orms, were recovered from AB erythrocytes. Analysing disialogangliosid es from red cells belonging to 17 genetically related cats, we consist ently obtained the expected disialoganglioside profile, based on blood typing and pedigree information. SDS-PAGE of red cell membrane protei ns and blotting with Triticum vulgaris, a lectin recognizing NeuNAc, r evealed glycoproteins of approximately 51, 53, and 80 kD in B and AB c ats but only a faint band of approximately 53 kD in A cats. By haemagg lutination, Triticum vulgaris could also distinguish different blood t ypes by specifically binding to B and AB cells. Flow cytometry showed that more anti-B bound to B cells than anti-A bound to A cells. Althou gh AB cells had a broad range of fluorescence when compared to the pro files seen with A and B cells, the mean fluorescence with AB cells was half of that seen with A or B. These results further characterize the antigens determining the feline A-B blood group system illustrating d ifferences between A, B and AB cats, and between homozygous and hetero zygous A cats.