Central immunological position of the human histo (blood) group O(H) phenotype.

Blood
group A phenotype development is associated with impaired formation of adaptive
and innate immunoglobulins due to clonal selection and phenotypic, glycosidic accommodation
of plasma proteins. Moreover, it is significantly burdened with an increased
risk of developing different types of cancer, while exerting strong
susceptibility to severe infection by <i>Plasmodium
falciparum</i>. Although the infection by <i>Plasmodium
vivax</i> is the best documented type of malaria,<i> P. falciparum </i>causes the most severe and frequent diseases. In both
malaria types, the risk of developing disease is molecularly strongly related
to phenotype formation, although with reverse outcomes. In fact, the Duffy
positive Fy (a+b+) individuals
are most susceptible to <i>P. vivax</i>
infection and the human blood group A
shows statistically significant susceptibility to severe <i>P. falciparum</i> infection runs<i>
</i>when compared with blood group O(H), however, while the Duffy
antigen receptor for chemokines (DARC) protein exerts a marked cancer regulating
activity, blood group A shows a significant susceptibility of cancer.
Aside from the well documented<b> </b>pathomechanism
characterizing the <i>P. vivax</i>
infections of Duffy positive individuals, in blood group A, in which the blood
group determining glycotransferase(s) assumingly affect the levels of anti-A/Tn
cross-reactive immunoglobulins, via the common "serine repeat
antigen" may also accomplish the entry of the parasite's merozoites into the host's red blood cells (RBC). The
blood group O(H) phenotype, which is currently discussed to have a survival advantage
of the overall risk of developing cancer, appears to offer the widest functional
flexibility in adaptive and germline-encoded innate immunity; it is the only
blood type that is superior in both controlling cancer growth and
life-threatening infection by a protozoan, and thus likely has survived as the
worldwide most common phenotype.