Precise specificity of induced tubular HLA-class II antigens in renal allografts.

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.