On Pestilence, Deit, Natural Selection, and the Distribution of Microbial and Human Blood Group Antigens and Antibodies

Abstract

Current theories relating the present distribution of ABO blood group frequencies to the selective action of habits of diet and to past screening by specific infectious diseases are open to question on several counts. Aboriginal diet areas in the New World fail to correlate geographically with ABO frequency as postulated. A considerable body of evidence contradictory to the hypothesis of selection by pestilence also exists. Blood group specificity, however, can be shown to figure in several areas of immunological significance. Recent serological studies indicate that former concepts relating to sites of ABH mucopolysaccharide deposition as well as to loci of active antibody formation and protection must be broadened alike. Antibodies in the form of IgA globulins, locally produced in lymphoid tissues, constitute a peripheral system of defense for the protection of mucous membranes. Studies on salivary antigens and antibodies indicate annual fluctuations in levels of production, with corresponding cycles of susceptibility and disease resistance. The possibility of a genetic polymorphism responsible for states of salivary antibody secretion or non-secretion, as proposed by some workers, is dismissed. A selective role for intestinal microbiota is suggested, operating differentially in the several ABO phenotypes. Dietary preferences, which also influence intestinal ecology since they largely determine the identity of floral types, may also function here to the advantage or disadvantage of the organism.