It has been shown that CD161+ cells are highly enriched in the synovial fluid of Juvenile Idiopathic Arthritis (JIA) patients, with CD161 expressed on several cell populations including Th17, Th17/1, and some Th1 cells (‘ex-Th17’ cells)1, regulatory CD4+ T cells2, some CD8 cells (e.g. MAIT cells), NK cells and innate lymphoid cells (ILC)3. Here, CD4 is linked to juvenile idiopathic arthritis.