CD4 and arthritic joint disease: These observations are in line with other recent studies in arthritis showing that synovial CD4+T cells and Treg clones can also be detected in PB (Rossetti et al., 2017; Spreafico et al., 2016), where their presence correlates with disease activity and response to therapy (Rossetti et al., 2017; Lutter et al., 2018).