Human erythrocyte acetylcholinesterase bears the Yt^a blood group antigen and is reduced or absent in the Yt(a-b-) phenotype

The Cartwright (Yt) blood group antigens have previously been shown likely to reside on a phosphatidylinositol-linked erythrocyte membrane protein. In this study, an unusual individual whose red blood cells (RBCs) were of the previously unreported Yt(a-b-) phenotype were used, along with normal Yt(a+) cells, to investigate serologically and biochemically the relationship of the Yt^a antigen to known phosphatidylinositol-linked erythrocyte proteins. Yt(a-b-) RBCs expressed normal amounts of various phosphatidylinositol-linked proteins except acetylcholinesterase. Further, human anti-Yt^a reacted with acetylcholinesterase in immunoprecipitation and immunoblotting studies. Thus, acetylcholinesterase is now identified as the protein bearing the Yt blood group antigens.