TNFRSF4 and autoimmune thrombocytopenic purpura: The frequencies of circulating OX40+CD4+ T cells among CD4+ T cells in ITP patients were significantly increased compared to those in HCs; in particular, the frequencies of circulating OX40+CD4+ T cells in ITP patients with positive antiplatelet autoantibodies were notably greater than those in ITP patients with negative antiplatelet autoantibodies (Figure 2(b)).