To characterize OX40 and OX40L expression and determine the role of OX40/OX40L signal in the development and pathogenesis of T1D, we evaluated the expression of sOX40 and sOX40L in the PBMC and sera of patients with T1D and healthy controls (HCs) and analyzed the correlation with clinical and inflammatory indicators. The gene discussed is TNFSF4; the disease is type 1 diabetes mellitus.