EFFECTS OF MHC-ENCODED TAP1 AND TAP2 GENE POLYMORPHISM AND MATCHING ON KIDNEY GRAFT-REJECTION

The products of TAP1 and TAP2 genes, recently mapped within the MHC cl ass II region, are involved in antigen presentation by MHC class I mol ecules, especially in the transport of endogenous peptides, As for mos t MHC genes, a polymorphism has been described and the possibility tha t it could influence the recipient immune response by modulating antig en presentation in kidney transplantation has been tested. The aim of our study was to compare TAP1 and TAP2 gene polymorphism and matching in 53 couples of kidney donors and recipients without any rejection ep isodes and in 55 other couples who had experienced at least 2 acute ce llular rejection episodes; 70 healthy individuals served as controls. Our results showed that allelic variant frequencies of TAP1 alleles (1 A to 1C) and TAP2 alleles (2A to 2E), as assessed by amplification ref ractory mutation system-polymerase chain reaction, were similar among ''rejection'' and ''no rejection'' populations, Furthermore, there wer e no differences of TAP1 and/or TAP2 matching between donors and recip ients in the 2 groups. In contrast, we showed that the recipients of t he no rejection group were better matched with their corresponding don ors for the HLA-DR genes than those of the rejection group. These resu lts suggest that the currently described polymorphism in the limited c oding region of TAP1 and TAP2 genes does not influence the incidence o f kidney allograft rejection episodes and seems not to be a strong lin k to the adjacent DR/DQ subregion. Moreover, the observed increase fre quency of TAP1B allele in the whole recipient's group as compared with controls (16.2% vs, 7.1% in the healthy individuals; P<0.02) was not linked to the rejection occurrence hut to the presence of glomerulonep hritis as initial disease. Our study suggests that, in the clinical co nditions tested, neither TAP polymorphism nor TAP matching influences the renal graft outcome.