Our studies provide further clarity on the origin of IFN-γ–producing CD4+ T cells in oligo JIA SF and whether classical Th1 (derived from naive CD4 T cells) or nonclassical Th1 cells (derived from Th17 cells) predominate in the joints of children with oligo JIA (13–16, 25). Here, CD4 is linked to juvenile idiopathic arthritis.