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 malaria infection. Both the risk of developing cancer and susceptibility to malaria disease appear molecularly to be strongly related to phenotype
... d to phenotype formation, in which the blood group A-determining glycotransferase(s) might affect the levels of anti-A/Tn cross-reactive immunoglobulins on the one side, and on the other side accomplish the contact and entry of the protozoan into the host via the "serine repeat antigen". Such contact, thus provided predominantly by blood group A cells, appears to be promoted also by cancer cells conducting "A-like" Tn formation, which is inhibited by Plasmodium invasion, why blood group A is extremely rare in regions, in which malaria is endemic but malaria infection inversely associated with cancerous growth. Consequently, the blood group O phenotype, currently discussed to have a survival advantage of the overall risk of developing cancer when compared with non-O blood groups, rarely develops severe malaria, and despite its susceptibility to severe cholera disease and exposure to extensive historical cholera pandemics, occurring over the centuries, has survived as the worldwide most common blood type, due to a complex, superior immunity.