Prokaryotic "blood group A/B-like" antigenic structures apparently induce exclusively cross-reactive anti-A/B immunoglobulins, which thus can neither arise in blood group A nor in B individuals, whereas the plasma proteins, involving the non-immune or "natural", polyreactive IgM, undergo the phenotype-specific glycosidic accommodation that excludes an essential anti-self reactivity. Consequently, the central immunological position of the human histo (blood) group O(H) becomes evident in its

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... rehensive presentation of both non-immune IgM and (largely restricted to this group) adaptive IgM/IgG antibodies against all non-O(H) blood groups, involving their cross-specific developmental and/or "aberrant" structures, as there are the early eukaryotic, trans-species O-glycans, T (Thomsen-Friedenreich) and Tn, "T nouvelle" antigen. These ancestral glycans arise from O-glycosylations that are, with similar peptide backbones, already used by lower eukaryotes, such as mollusks and the fruit fly Drosophila melanogaster, moreover, in the snail Helix pomatia are associated with the release of the hexamerically structured anti-A/Tn-reactive agglutinin.