Expression of ABH, Lewis and related tissue antigens in the human thymus.

Expression of ABH, Lewis and related antigens was studied in the thymus of children of known ABO, Lewis and secretor status using a panel of specific reagents. ABH and Lewis antigens partly under control of the secretor status were expressed on the Hassals' bodies and a large fraction of the medullary epithelial cells. The sialyl-Lea antigen was only present on some Hassals' bodies of Lewis-positive individuals. ABH but not Lewis antigens were also present on cortical epithelial cells but this was independent of the secretor status. The X, sialyl-X and Y antigens were only expressed on Hassals' bodies irrespective of the ABO, Lewis or secretor phenotype. Furthermore, the anti-X and sialyl-X antibodies labelled a subset of leucocytes of all the individuals tested. These results show that the genetic control of the expression of ABH and Lewis glycosidic tissue alloantigens in the thymus is different on cortical and medullary epithelial cells and stress the heterogeneity of the thymus epithelial cells.