DEFINITION, GENETICS, AND POSSIBLE SIGNIFICANCE OF A NEWLY DEFINED EDOTHELIAL ANTIGEN IN THE RAT

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Abstract
A non-major-histocompatibility-complex (MHC) endothelial antigen system was defined in the rat and the genetics of these antigens as well as their significance in renal transplantation were studied. Several MHC-identical rat strain combinations underwent reciprocal immunization using spleen and lymph node cells and complete Freund''s adjuvant. In 1 combination (MAXX anti-BN) alloantibodies were found against antigens on peritubular and venous endothelium of the kidney from the immunizing strain and from 2 other strains. The endothelial antigen is probably present on monocytes but not on nonstimulated T and B lymphocytes. With kidneys from 7 MHC-congenic lines, the endothelial antigens are encoded outside the MHC-region. The antigen seems to be expressed as a dominant trait. In an F2 population of 32 animals, segregation of the endothelial antigen or antigens appeared to be independent of the MHC, AgF and tubular basement membrane antigens, as well as the locus for albinism. Transplantation of MHC-identical but endothelial-antigen-incompatible kidneys into nonimmunized recipients did not provoke acute rejection. Pretransplant immunity against donor endothelial antigens was associated with accelerated acute rejection. The rejection was donor-specific because 3rd-party MHC-incompatible but endothelial-antigen-compatible kidneys were rejected like 1st-set grafts. Graft rejection in presensitized recipients of an MHC-identical kidney can be mediated through immunity against non-MHC antigens.