Clinical significance of the ratio between FOXP3 positive regulatory T cell and interleukin-17 secreting cell in renal allograft biopsies with acute T-cell-mediated rejection

The aim of this study is to investigate the clinical significance of the ratio between interleukin-17 (IL-17) secreting cell and FOXP3-positive regulatory T cell (FOXP3 ⁺ Treg) infiltration in renal allograft tissues with acute T-cell-mediated rejection (ATCMR). Fifty-six patients with biopsy-proven ATCMR were included. Infiltration of FOXP3 ⁺ Treg and IL-17-secreting cells was evaluated with immunostaining for FOXP3 or IL-17 on the biopsy specimens, and the patients were divided into the FOXP3 high group (Log FOXP3/IL-17>0·45) or the IL-17 high group (Log FOXP3/IL-17<0·45). We compared the allograft function, severity of tissue injury, and clinical outcome between the two groups. In the IL-17 high group, allograft function was significantly decreased compared with the FOXP3 high group (P<0·05). The severity of interstitial and tubular injury in the IL-17 high group was higher than the FOXP3 high group (P<0·05). The proportions of steroid-resistant rejection, incomplete recovery and recurrent ATCMR were higher in the IL-17 high group than in the FOXP3 high group (all indicators, P<0·05). The IL-17 high group showed lower 1-year (54% versus 90%, P<0·05) and 5-year (38% versus 85%, P<0·05) allograft survival rates compared with the FOXP3 high group. Multivariate analysis revealed that the FOXP3/IL-17 ratio was a significant predictor for allograft outcome. The FOXP3/IL-17 ratio is a useful indicator for representing the severity of tissue injury, allograft dysfunction and for predicting the clinical outcome of ATCMR.