Chemistry, Distribution, and Function of Blood Group Substances

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Abstract
The ABH blood group substances include several chemically diverse macro-molecular species identical only with respect to their antigenic sites. The latter can now be visualized in terms of definite territories of a polysaccharide chain synthesized under the aegis of Lewis, H (together with the Se (secretor) gene in many water-soluble substances), and A, B genes by sequential additions of single sugars. Multiple specificities within the ABH, Lewis system are visualized as due to the variable efficiency of the transferases concerned, allowing for some chains upon a macromolecule to remain "unifinished." The secretor: non-secretor status is interpreted as dependent upon the biosynthesis of the saccharide chains proceeding beyond the "primitive substance" (pneumococcus XIV) or Lea stage. The all-or-none view of this ability must now be modified, since several secretions, including mucus in some topographical locations within the gastrointestinal tract, bear the complete chains with H and A, B specificities, irrespective of secretor status. The wide distribution of the epithelial cell wall substances in embryonal and early fetal life and the subsequent waning of the antigens (and, therefore, presumably of the whole substance) suggests that they fulfill a function in organogenesis and in the early maturation of the anlagen. The other substances, as gleaned from their morphological features and behavior, belong to different molecular species and subserve functions as yet unknown. Research is just starting on other blood group substances, Rhesus, and M, N, employing the concepts and techniques developed in investigations of the ABH. Lewis system.