Regulatory T cell (Treg) therapy has shown promises in experimental models of type 1 diabetes (T1D) and other autoimmune diseases. Now, Bluestone et al. (2015) report in a phase 1, dose-escalation study that ex vivo-expanded autologous polyclonal Treg therapy is safe and well tolerated in adult patients with recent-onset T1D. © 2016 Elsevier Inc.