Looking into the Graft without a Biopsy: Biomarkers of Acute Rejection in Renal Transplantation.

Immunosuppression in kidney transplantation is still largely driven by center-specific protocols and adjusted according to the presence of graft dysfunction, drug toxicity or infection. Due to the current inability to titrate immunosuppression to the needs of every single patient, this approach is burdened by an increased risk of under or over-immunosuppression. To extend allograft survival, immunosuppression should be decided based on reliable biomarkers capable of quantifying the alloimmune response and/or noninvasively diagnosing acute rejection. Emerging data indicate that many assays, likely used in panels rather than singularly, have potential to be diagnostic and predictive of short- and also long-term outcomes. Many cross-sectional and retrospective studies showed associations between these biomarkers and clinically relevant post-transplantation outcomes, but data from prospective studies are still scarce, thereby preventing widespread implementation in the clinic. Prospective, randomized, multicenter studies are currently ongoing to test the hypothesis that biomarker-driven immunosuppression provides better outcomes than standard, protocol-driven immunosuppression. These projects and other future studies are highly warranted to improve outcomes of kidney transplant patients.