Association of blood groups and disease: do blood group antigens and antibodies have a biological role?

Although there are probably over a thousand publications on the associations of blood groups and disease, many are based totally on statistical analyses. Most of the earlier studies have been controversial, because they were small studies and/or had inadequate controls and/or had been analyzed incorrectly. Nevertheless, it is difficult to argue with the general pattern that emerges from the large body of statistical data on malignancy, coagulation and infection. Recent findings in membrane chemistry, rumor immunology and infectious disease (especially relating to bacterial receptors), add a scientific rationale for some of these findings, and there is an increasing rationale for some of the earlier statistical findings. Some of the more recent findings on parasitic/bacterial/viral receptors, the hematological abnormalities seen when high frequency blood group antigens are missing, and the association with immunologically important proteins are most convincing and suggest that blood group antigens do sometimes play a biological role; this role may relate directly, or often be completely unrelated, to the red cell.