To elucidate the functional characteristics of circulating CXCR5+γδ T cells, we next detected the expression levels of the costimulatory molecules ICOS and CD40l on these cells in ITP pediatric patients (n = 96) and healthy controls (n = 48) by FCM. The gene discussed is CXCR5; the disease is autoimmune thrombocytopenic purpura.