Schematic representation of biosynthesis of blood group A, B, FORS1, and related antigens. The biosynthetic pathways of blood group A, B, FORS1, and related glycan antigens are schematically shown. The gene names, glycan names, and transferase names are shown in light blue, dark blue, and purple, respectively. Important genes/transferases/glycans are shown in bold. The immunodominant epitopes of A, B, and FORS1 are shown in red and bold.