Genetic control of the fucosylation of ABH precursor chains. Evidence for new epistatic interactions in different cells and tissues.

The general structure of the ABH antigens is analysed taking into account six possible precursor chains and two alpha-2-fucosyltransferases. The classical genetic model with one structural gene and two regulatory genes for the synthesis of the H antigen and the events which prompted the proposal of the new model with two structural genes for the synthesis of H determinants are discussed. Three human alpha-3-fucosyltransferases with different acceptor specificity are presented. Myeloid type of alpha-3-fucosyltransferase, which transfers fucose on to H type 2, serum type of alpha-3-fucosyltransferase, which transfers fucose on to H type 2 and sialyl-N-acetyl-lactosamine and Lewis or alpha-3/4-fucosyltransferase, which transfers fucose on to H type 1 and H type 2 and the corresponding sialylated structures. The presence of different ABH and Lewis antigens in different tissues and the different epistatic interactions needed to account for their synthesis are analysed in terms of new epistatic interactions with either the known fucosyltransferases or with new fucosyltransferases.