Background. Cytotoxic T-lymphocyte antigen 4 (CTLA4) has been shown to play a critical role in the down-regulation of the immune response. We retrospectively examined the association between acute rejection and two polymorphisms in the CTLA4 gene, the dinucleotide (AT)n repeat polymorphism in exon 3 and the single nucleotide polymorphism A/G at position 49 in exon 1, in a cohort of liver and kidney transplant recipients. Methods and Results. A total of 207 liver and 167 renal transplant recipients were analyzed. In the case of the (AT)n repeat polymorphism we found an increased incidence of acute rejection in association with allele 3 and 4 in both liver and kidney (P=0.002 and 0.05, respectively). In addition, in liver transplant recipients, allele 7 was associated with acute rejection independent of ethnicity (P<0.05). Allele 1 was less frequently observed in African American as compared with Caucasian liver and kidney transplant recipients, with a frequency of 33.8% and 69%, respectively (P<0.0001). Those patients with allele 1 had a tendency toward a lower rate of rejection at 42% versus 57.8% (P=0.058), suggesting a potential protective effect of allele 1. Analysis of the A/G single nucleotide polymorphism demonstrated no association between either allele and the incidence of acute rejection in the patients studied. Conclusion. These initial observations provide the necessary basis to further investigate the risk stratification of transplant recipients based on specific CTLA4 gene polymorphisms.
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