Previous studies have shown that infiltrating innate immune cells like macrophages and adaptive immune cells such as CD4+ T cells and B cells in sublining synovium contributes to arthritis pathogenesis, as elimination of macrophages, CD4+ T cells, or B cells prevents arthritis development (Solomon et al., 2005; Svensson et al., 1998; Taneja et al., 2002). Here, CD4 is linked to arthritic joint disease.