Type 1 diabetes (T1D) is one of the major autoimmune diseases affecting children and young adults worldwide. To date, the different immunotherapies tested have achieved insulin independence in <5% of treated individuals. Recently, a novel hematopoietic stem cell (HSC)–based strategy has been tested in individuals with new-onset T1D. The aim of this study was to determine the effects of autologous nonmyeloablative HSC transplantation in 65 individuals with new-onset T1D who were enrolled in two Chinese centers and one Polish center, pooled, and followed up for 48 months. A total of 59% of individuals with T1D achieved insulin independence within the first 6 months after receiving conditioning immunosuppression therapy (with antithymocyte globulin and cyclophosphamide) and a single infusion of autologous HSCs, and 32% remained insulin independent at the last time point of their follow-up. All treated subjects showed a decrease in HbA_1c levels and an increase in C-peptide levels compared with pretreatment. Despite a complete immune system recovery (i.e., leukocyte count) after treatment, 52% of treated individuals experienced adverse effects. Our study suggests the following: 1) that remission of T1D is possible by combining HSC transplantation and immunosuppression; 2) that autologous nonmyeloablative HSC transplantation represents an effective treatment for selected individuals with T1D; and 3) that safer HSC-based therapeutic options are required.

Restoration of a PD-L1 defect in HSPCs reverses diabetes in NOD mice and thus may represent a potential cure for T1D.

Podocyte injury and resulting albuminuria are hallmarks of diabetic nephropathy, but targeted therapies to halt or prevent these complications are currently not available. Here, we show that the immune-related molecule B7-1/CD80 is a critical mediator of podocyte injury in type 2 diabetic nephropathy. We report the induction of podocyte B7-1 in kidney biopsy specimens from patients with type 2 diabetes. Genetic and epidemiologic studies revealed the association of two single nucleotide polymorphisms at the B7-1 gene with diabetic nephropathy. Furthermore, increased levels of the soluble isoform of the B7-1 ligand CD28 correlated with the progression to ESRD in individuals with type 2 diabetes. In vitro, high glucose conditions prompted the phosphatidylinositol 3 kinase–dependent upregulation of B7-1 in podocytes, and the ectopic expression of B7-1 in podocytes increased apoptosis and induced disruption of the cytoskeleton that were reversed by the B7-1 inhibitor CTLA4-Ig. Podocyte expression of B7-1 was also induced in vivo in two murine models of diabetic nephropathy, and treatment with CTLA4-Ig prevented increased urinary albumin excretion and improved kidney pathology in these animals. Taken together, these results identify B7-1 inhibition as a potential therapeutic strategy for the prevention or treatment of diabetic nephropathy.

Impaired regulatory B cell (Breg)-responses are associated with several autoimmune diseases in humans; however, the role of Bregs in type 1 diabetes (T1D) remains unclear. We hypothesized that naturally occurring, interleukin-10 (IL-10) producing Bregs maintain tolerance to islet autoantigens, and that hyperglycemic nonobese diabetic (NOD) mice and T1D patients lack these potent negative regulators. IgV_H transcriptome analysis revealed that islet-infiltrating B cells in long-term normoglycemic (Lnglc) NOD, which are naturally protected from diabetes, are more antigen-experienced and possess more diverse B-cell receptor repertoires compared to those of hyperglycemic (Hglc) mice. Importantly, increased levels of Breg-promoting CD40⁺ B cells and IL-10-producing B cells were found within islets of Lnglc compared to Hglc NOD. Likewise, healthy controls showed inreased frequencies of both CD40⁺ and IL-10⁺ B cells compared to T1D patients. Rituximab-mediated B-cell depletion followed by adoptive transfer of B cells from Hglc mice induced hyperglycemia in Lnglc hCD20(^+/+) NOD mice. Importantly, both murine and human IL-10⁺ B cells significantly abrogated T cell–mediated responses to self or islet-specific peptides ex vivo. Together, our data suggest that antigen-matured Bregs may maintain tolerance to islet autoantigens by selectively suppressing autoreactive T-cell responses, and that Hglc mice and individuals with T1D lack this population of Bregs.