The aim of the present study was to determine whether a kidney graft expressing the glutathione S-transferase T1 enzyme (GSTT1) could cause an alloimmune response in a recipient with the null GSTT1 genotype that was similar to that observed in liver transplant. We have found anti-GSTT1 antibodies in the sera of a number of patients and confirmed that only one of the four possible genetic combinations--positive donor/null receptor--could lead to the production of these antibodies. Nevertheless, the main finding of this study is that in kidney transplantation, this mismatch was not sufficient to trigger an immune reaction. Longer follow-up of the posttransplant evolution of the patients is required in order to clarify the contribution of the factors involved in this process.