PRECISE SPECIFICITY OF INDUCED TUBULAR HLA-CLASS II ANTIGENS IN RENAL ALLOGRAFTS

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Abstract
HLA—class II antigen expression is induced in the tubules of renal allografts, but it is unclear whether all three class II products—HLA-DR, DQ, and DP—are induced, and whether the induced product is of donor origin. A pretransplant (n=14) and serial transplant biopsies (n=45) were obtained from 14 transplant recipients in whom induced HLA-class II antigen was detected after transplantation with a monoclonal antibody reactive with HLA-DR, DP, and possibly DQ antigens. Cryostat sections were stained with locus-specific or polymorphic monoclonal antibodies in an indirect immunoperoxidase assay. In pretransplant biopsies intracellular HLA-DR antigen was expressed on proximal tubules, whereas all tubules were negative for HLA-DQ and DP products. After transplantation grafts with induced tubular HLA—class II antigen had induced HLA-DR, DQ and DP antigens expressed both within the cytoplasm and on the cell membranes. The donor or recipient origin of induced HLA—class II expression was determined using polymorphic antibodies specific for either donor or recipient antigens. This approach demonstrated that the induced class II antigen is of donor origin—and, furthermore, that the renal parenchyma remains of donor HLA-type, even one year after transplantation, and thus remains a source of antigenic stimulus to the recipient.