ABH and related tissue antigens.

The genetic model proposing that H and Se are two closely linked structural genes, coding for two distinct 0[-2-~fucosyltransferases (Oriol et al., 198 I), is strongly supported by recent results from three different laboratories (Kumazaki & Yoshida, 1984; Betteridge 8c Watkins, 1985; Le Pendu e ta / . , 1985). This suggests that there must be, at least, two different cr-2-~-fucosyltransferases. Based on the immunofluorescence results obtained on different tissues of donors of known ABO, H, secretor, Lewis and X phenotypes, we now propose a general pattern for the genetic control of the expression of ABH and related tissue antigens according to the embryological origin of each tissue. Ectodermal tissues express mainly ABH antigens independent of the Le and Se genes, whereas endodermal tissues express mainly ABH antigens under control of the products of the Le and Se genes (Oriol et al., 1986). Among the endodermal tissues, most of the cells of digestive, respiratory and urinary epithelia express ABH antigens under the control of the products of the ABO, Se and Le loci. Two embryonal layers are derived from the primitive ectoderm, these being neuroectoderm and mesoderm which originates from an invagination of the ectoderm in the 16-day-old embryo. Of the mesodermal tissues, vascular endothelium, erythrocytes and platelets possess intrinsic ABH antigens. Of the neuroectodermal tissues, the epidermis and the primary sensory cells, which are derived from the placodes and the neural crest, also express ABH antigens. In all these ectodermal tissues the ABH antigens expressed are under the control of the ABO locus, but they are independent of the Se and Le genes. A few examples of different tissues are detailed below to illustrate the findings