Abstract
The H antigen was mapped out by immunofluorescence in human tissues (including those of fetuses from 15 cm crown-heel length) from individuals of the various groups within the ABO system, both secretors and non-secretors. The distribution of the antigen can be summarized under the following headings: Cell walls of endothelium: present throughout the cardiovascular system; Cell walls of stratified epithelia: in skin, non-cornifying squamous stratified membranes, transitional epithelia; Mucus: occurring wherever the latter is produced in secretor individuals and confined to a few special topographical areas in non-secretors; Secretions and excretions: the pancreatic and sudoriferous (independent of secretor status), and mammary and uterine (governed by the secretor makeup) all contain it. The distribution of the H antigen is most fully represented in tissues of group O. It follows an over-all universal pattern, characteristically modified in non-secretors, equally valid for antigens A and B described in a preceding study. Within this pattern, in tissues of the non-O groups, the complement of the H substance in its various forms wanes in a manner consistent with the hypothesis that it serves as a substrate for the A(1), A(2), B genes, exerting their action with different degrees of efficiency. The secretor:non-secretor phenomena can be most simply interpreted by viewing the non-secretor, recessive gene (in the homozygous, ss condition) as inhibiting the production of some of the water-soluble forms of the blood group substances. Since the gene was never found responsible for dissociation of the H and A, B antigens its inhibitory action is thought to be wrought at the point of formation of the basic H substance or its precursor.