TNFSF11 and juvenile idiopathic arthritis: Moreover, regarding IL-17A, our findings are in line with previous studies by our group and others.10 64 70 IL-17A is a potent proinflammatory cytokine, produced mainly by Th17 cells, that has been found to be highly expressed in the inflamed synovium and strongly contributes to the production of several other proinflammatory cytokines (such as IL-6 and RANKL), therefore amplifying the inflammatory cascade and contributing to tissue destruction.71 72 The elevated IL-17A serum levels found in this study support a role of this cytokine, Th17 and/or Th17-like Tfh cells in JIA development.