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. 2004 May 10;12(6):279–287. doi: 10.1016/j.tim.2004.04.005

Figure 2.

Figure 2

ABH and Lewis antigens are synthesized by sequential enzymatic transfer of single carbohydrate residues to specific precursor carbohydrate substrates. (a,b) H antigens are made by enzymatic addition of a fucose (Fuc) residue to the terminal galactose (Gal) residue in α1,2 linkage. (a) Secretor positive (Se+) individuals express the FUT2 gene product, a fucosyltransferase that adds Fuc to a type 1 precursor to make H type 1 (also known as Lewis(d) or Led). Eighty percent of Northern Europeans and Caucasian Americans are Se+. (b) The FUT1 fucosyltransferase adds Fuc to a type 2 precursor to make H type 2. Less than 0.002% of people throughout the world lack FUT1 expression; they also do not express H antigen on their red blood cells (histo-blood group type Bombay), which is normally expressed on type O red blood cells. Type 1 and 2 precursor substrates have different Gal to N-acetylglucosamine (GlcNAc) linkages, (a) Galβ1,3-GlcNAcβ- and (b) Galβ1,4-GlcNAcβ-, respectively. The Lewis carbohydrate antigens are made when the FUT3 enzyme is expressed in Lewis positive (Le+) individuals. Eighty percent of Northern Europeans and Caucasian Americans individuals are Le+, independent of secretor status. (a,b)FUT3 transfers Fuc to the GlcNAc of type 1 and 2 precursors and H types 1 and 2 in α1,4 and α1,3 linkages, respectively. (c) H types 1 and 2 are the terminal moieties expressed in histo-blood group type O individuals, but in types A, B and AB individuals the H antigens are further modified by enzymes that transfer N-acetylgalactosamine (GalNAc, type A), Gal (type B), or either carbohydrate (type AB) to the terminal Gal residue of an H antigen in α1,3 linkage. ABH, Lewis and secretor phenotypes and enzymatic pathways are described in greater detail in other reviews 55, 56.