To determine whether OPG and DMB could protect human β cells against T1D serum–induced cytotoxicity, dispersed human islet cells cultured in medium containing FCS, human T1D, or ND serum were treated with either vehicle or IgG as controls, and OPG (Fig. 9C) or DMB (Fig. 9D), and assayed for β cell death after 24 hours. The gene discussed is TNFRSF11B; the disease is type 1 diabetes mellitus.