Figure 5. Blood group antigens.
Each tetra-saccharide can be divided in two distinct fucosylated tri-saccharides: Leb in a H type-1 tri-saccharide --Fucα2Galβ3GlcNAc— and in a Lewis-a (Lea) tri-saccharide --Galβ3[Fucα4GlcNAc]— and Ley in a H type-2 tri-saccharide --Fucα2Galβ4GlcNAc— or in a Lex tri-saccharide --Galβ4[Fucα3GlcNAc]—.