Distribution of the major histocompatibility complex antigens in human and rat kidney

We have compared the distribution of the major histocompatibility complex (MHC) antigens in human and rat kidney using monospecific antisera to class I and II antigens of the MHC. FITC/TRITC double immunofluorescence was used to demonstrate these antigens in frozen sections and the Staphylococcus aureus Cowan I rosette assay on the cell surface. In both species, the MHC antigens were prominently present on the passenger leukocytes. Immunofluorescence analysis of human kidney demonstrated that the class I, beta 2-microglobulin (beta 2m), and class II antigens were present in the vascular endothelial cells and class I antigens in the renal tubular cells. The Staphylococcus assay demonstrated that these antigens were also exposed on the respective cell surfaces. In clear contrast, in the rat, class I, the beta 2m, and class II antigens were absent from the kidney vascular endothelium of large vessels and intertubular capillaries; however, large amounts of class II antigens were seen inside the proximal renal tubular cells. The Staphylococcus assay indicated that none or very little of these antigens were exposed on the kidney parenchymal cell surface. These differences may explain why rat renal transplants are relatively non-immunogenic and easily accepted, whereas human renal transplant recipients must be immunosuppressed ad infinitum.