Chapter 6 The Abh Blood Groups and Development

Abstract

Publisher Summary This chapter focuses on ABH blood groups and their development. The ABH antigens are widely distributed in the tissues of the human embryo/fetus from the earliest ascertainable stages of development—fifth week post-fertilization. They are not only present on the surfaces of the erythrocytes but also, in large amounts, on the cell surfaces of the endothelium and of the epithelia of most early organs. While their physiologic function remains unknown, it is their early appearance in embryonal life and wide distribution in most epithelial primordia that causes them to be of interest in human reproduction. Of the vast and growing number of known antigenic systems of man, the ABH is the best understood in terms of both genetics and biochemistry. The ABH substances of the erythrocytes and of the mucoid secretions are characterized to a large extent and can be visualized as belonging to several families of macromolecules, either glycoprotein or glycolipid. The blood group antigens ABH represent a variety of macromolecules, all associated with the surface of the cell membrane. Their biological significance, pointed to by the increased hazards in ABO incompatible feto-maternal matches, is interpreted in the light of an hypothesis that views the A/B antigens as potential targets for maternal immunoglobulin (IgG) antibodies crossing by diffusion the early placental barrier.