Introduction DNA methylation is a well-known epigenetic mechanism which plays a critical role in cell function by regulating gene expression. Variations in DNA methylation are increasingly associated with diseases, including immune-mediated diseases. However, the role of DNA methylation in organ transplantation is unknown. Here, we studied the methylation of regulatory cytosine phosphate guanine sites (CpGs) in genes involved in alloreactivity; the pro-inflammatory cytokine interferon γ (IFNγ) and the co-inhibitor molecule programmed death 1 (PD1) in kidney transplantation patients. Methods The DNA methylation of regulatory CpGs (2 for IFNγ and 8 for PD1) was determined with pyrosequencing in FACS sorted naïve, central memory (CM), effector memory (EM) and EMRA CD8+ T cells before, 3 months and 12 months after kidney transplantation. Both patients who developed a biopsy proven acute rejection within the first three months after transplantation (rejectors; n=5) and patients who remained free from rejection (non-rejectors; n=5) were included. As infection with cytomegalovirus (CMV) may significantly alter the methylation of IFNγ, only CMV seronegative kidney transplantation patients and healthy donors (n=5) were studied. Results Both IFNγ and PD1 were significantly (p<0.001) higher methylated in the naïve CD8 T cells compared to the memory subsets (IFNγ: 55% in naïve versus 16% in CM, 12% in EM and 6% in EMRA; PD1: 43% versus 17%, 11% and 12%, respectively). Before transplantation the methylation status of both IFNγ and PD1 was comparable to healthy donors in the CD8+ T cell subsets. Remarkably, the methylation status of the different CpGs of both IFNγ and PD1 did not significantly change during the immunologically challenging first year after transplantation. Additionally, comparing rejectors with non-rejectors did not demonstrate significant differences for either the methylation of IFNγ or PD1. Conclusion Patients with chronic kidney disease with subsequent 1 year follow-up after kidney transplantation did not demonstrate significant alterations in DNA methylation of either IFNγ, or PD1 in CD8+ T cells compared to healthy individuals. Based on these findings we conclude that variations in DNA methylation of either IFNγ or PD1 is not associated with allograft rejection after kidney transplantation.

CITATION INFORMATION: Boer K, de Wit E, Hesselink D, Hofland L, Betjes M, Baan C. The Impact of Allograft Rejection on DNA Methylation After Kidney Transplantation. Am J Transplant. 2016;16 (suppl 3).

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