IL17A and juvenile idiopathic arthritis: These findings are in agreement with several studies describing an accumulation of Th1 cells in the SF of JIA patients (25, 26), characterized as Th cells producing IFN-γ but without any distinction between the classic and non-classic phenotypes Additional data at epigenetic level confirm that non-classic Th1 cells originate from Th17 (41); indeed it was observed that non-classic Th1 cells exhibit demethylation of RORC2 and IL17A genes, as reported for Th17 cells, whereas classic Th1 cells are completely methylated at these loci (41).