Interleukin-17 positive cells accumulate in renal allografts during acute rejection and are independent predictors of worse graft outcome.

Interleukin-17 (IL-17) plays an important role in the regulation of cellular and humoral immune responses. Recent studies suggest a role for IL-17 in transplantation. Our study investigated whether quantifying IL-17(+) cells in renal transplant biopsies during acute rejection could have additional prognostic value for better stratifying patients at risk for nonresponsiveness to anti-rejection therapy and future graft dysfunction. Forty-nine renal biopsies with acute rejection were double immunostained and quantitatively analyzed for IL-17 and CD3 (IL-17(+) T-lymphocytes), tryptase (IL-17(+) mast cells) or CD15 (IL-17(+) neutrophils). Total IL-17(+) cell count correlated with total percentage of inflamed biopsy and estimated GFR during rejection. Most IL-17(+) cells were mast cells and neutrophils. We could hardly find any IL-17(+) T-lymphocytes. IL-17(+) mast cells correlated with interstitial fibrosis/tubular atrophy (IF/TA). None of the IL-17(+) cell counts had an additional prognostic value for response to anti-rejection treatment. Multivariate analysis correcting for C4d positivity and time from transplantation to biopsy showed that total IL-17(+) cell count independently predicts graft dysfunction at the last follow-up, which was validated in an independent cohort of 48 renal biopsies with acute rejection. We conclude that intragraft IL-17(+) cell count during acute allograft rejection could have an additional value for predicting late graft dysfunction.