CTLA4 and autoimmune thrombocytopenic purpura: monitored plasma levels of CTLA-4 in 37 patients with ITP who received 40 mg/day dexamethasone for four consecutive days and found that CTLA-4 levels were significantly elevated in not only patients with acute ITP, but also responders with acute ITP, suggesting that CTLA-4 might be associated with the pathogenesis of acute ITP and reflect treatment efficacy [28].