ABH antigens in vascular endothelium and some epithelial tissues of baboons

In baboons ABH antigens are found on vascular endothelium but not on red blood cells. This newly observed pattern of distribution is intermediate between that of lower mammals (in which ABH antigens are not found on endothelia or on red cells) and that of humans (in whom ABH antigens are present on both). In both types of cells the expression of these ABH antigens was expected to be under the same H-h genetic control, but the dissociation between the expression of ABH on red cells and on vascular endothelium shows that some other factor must by involved. The ABH antigens of exocrine secretions were expected to be under control of the Se-se system. However, some epithelial structures express ABH antigens in nonsecretor baboons (e.g., striated ducts), some cells express only H without A or B (e.g. biliary ducts and acinar cells of salivary glands), and some cells express only the H antigen at early stages of differentiation and the A or B antigens at later stages of differentiation (e.g. epidermis). ABH antigens were also found in the nervous system, a previously unreported site. All of these observations necessitate a reappraisal of current theory of the genetic control of tissue expression of ABH antigens.