Recognizes the blood group H type 2 antigens, trisaccharide Fuc? ?1-2Gal? ?1-4GlcNAc? ?1 of human origin. This protein is the basis of the ABO blood group system. The histo-blood group ABO involves three carbohydrate antigens: A, B, and H. A, B, and AB individuals express a glycosyltransferase activity that converts the H antigen to the A antigen (by addition of UDP-GalNAc) or to the B antigen (by addition of UDP-Gal), whereas O individuals lack such activity. It is expressed on endothelial cells, epithelial cells and granulocytes. Increased expression of this antigen has been observed on some tumor tissues such as gastric carcinomas, urothelial carcinomas, and colon carcinomas.