OBJECTIVE Type 1 diabetes is a condition in which pancreatic islets are destroyed by self-reactive T cells. The process is facilitated by deficits in the number and suppressive activity of regulatory T cells (Tregs). Here, we show for the first time that the infusion of autologous Tregs prolongs remission in recently diagnosed type 1 diabetes in children. RESEARCH DESIGN AND METHODS We have administered Tregs in 10 type 1 diabetic children (aged 8–16 years) within 2 months since diagnosis. In total, 4 patients received 10 × 10⁶ Tregs/kg body wt, and the remaining 6 patients received 20 × 10⁶ Tregs/kg body wt. The preparation consisted of sorted autologous CD3⁺CD4⁺CD25^highCD127⁻ Tregs expanded under good manufacturing practice conditions. RESULTS No toxicity of the therapy was noted. A significant increase in the percentage of Tregs in the peripheral blood has been observed since the day of infusion. These patients were followed along with matched type 1 diabetic patients not treated with Tregs. Half a year after type 1 diabetes onset (4–5 months after Tregs infusion), 8 patients treated with Tregs still required <0.5 UI/kg body wt of insulin daily, with 2 patients out of insulin completely, whereas the remission was over in the nontreated group. In addition, plasma C-peptide levels were significantly higher in the treated group as compared with those not treated. CONCLUSIONS This study shows that the administration of Tregs is safe and tolerable in children with recent-onset type 1 diabetes.

Improper activation of the immune system contributes to a variety of clinical conditions, including autoimmune and allergic diseases as well as solid organ and bone marrow transplantation. One approach to counteract this activation is through adoptive therapy with regulatory T cells (T_regs). Efforts to manufacture these cells have led to good maunfacturing practice–compliant protocols, and T_reg products are entering early clinical trials. Here, we report the stance of the European Union Cooperation in Science and Technology Action BM1305, “Action to Focus and Accelerate Cell-based Tolerance-inducing Therapies—A FACTT,” which identifies hurdles hindering T_reg clinical applications in Europe and provides possible solutions.