Influence of cytokine gene polymorphisms on kidney transplant outcome : the case of IFN-γ.

Samples from 93 of 115 consecutive cadaveric renal transplants were selected to define polymorphisms in both IFN-γ and IL-10. A 12 CA repeat IFN-γ polymorphic allele was found in 73 patients (70 in patients analysed further). This polymorphism was associated with high IFN-γ production in vitro. According to the presence or not of the 12 CA repeat allele patients were separated in high and low producer genotype groups. The incidence of acute rejection was 54.3% in this high IFN-γ genotype group, contrasting with 44.4% in the low IFN-γ. Requirement for ATG therapy was greater in the high IFN-γ group (odds ratio [OR]=2.5). Among HLA-DR-mismatched patients, IFN-γ high producer genotype was more strongly associated with rejection (OR=1.6). In the cyclosporine monotherapy subgroup, 11 out of 14 patients with IFN-γ high genotype (78%) had acute rejection (OR=2.88, p=0.09). Graft survival was similar between the two IFN-γ groups. When the analysis was controlled for the presence of delayed graft function, 40.5% of the high IFN-γ genotype patients had serum creatinine levels above 200 micromoles/L contrasting with only 14.3% of the low IFN-γ genotype recipients at 5 years after transplantation (p=0.05). In a regression model of creatinine at 1 year the significant variables were the presence of DGF, donor age greater than 50, greater than two rejection episodes, DR mismatch, donor female to male recipient sex, IL-10 high genotype, and IFN-γ high genotype. Conclusion: The 12 CA repeat IFN-γ polymorphic allele is associated with high IFN-γ production. We have shown that this high producer genotype for IFN-γ influences acute rejection in kidney transplantation, particularly in high-risk groups; it is also associated with worse long-term graft function