Specific therapy with modulated DC may restore immunological tolerance, thereby obviating the need for chronic immunosuppression in transplantation or autoimmunity. In this study we compared the tolerizing capacity of dexamethasone (Dex)‐ and 1α,25‐dihydroxyvitamin D3 (VD3)‐modulated DC. Treatment of monocytes with either VD3 or Dex resulted in DC with stable, semi‐mature phenotypes compared with standard DC, with intermediate levels of co‐stimulatory and MHC class II molecules, which remained unaltered after subsequent pro‐inflammatory stimulation. IL‐12p70 secretion was lost by VD3‐ and Dex‐DC, whereas IL‐10 secretion was unaffected. VD3‐DC distinctly produced large amounts of TNF‐α. Both VD3‐ and Dex‐DC possessed the capacity to convert CD4 T cells into IL‐10‐secreting Treg potently suppressing the proliferation of responder T cells. However, only Treg induced by VD3‐DC exhibited antigen specificity. VD3‐, but not Dex‐, DC expressed significant high levels of PD‐L1 (programmed death‐1 ligand), upon activation. Blockade of PD‐L1 during priming redirected T cells to produce IFN‐γ instead of IL‐10 and abolished acquisition of regulatory capacity. Our findings demonstrate that both VD3‐ and Dex‐DC possess durable but differential tolerogenic features, acting via different mechanisms. Both are potentially useful to specifically down‐regulate unwanted immune responses and induce immune tolerance. These modulated DC appear suitable as adjuvant in antigen‐specific clinical vaccination intervention strategies.

The clinical diagnosis of new-onset type 1 diabetes has, for many years, been considered relatively straightforward. Recently, however, there is increasing awareness that within this single clinical phenotype exists considerable heterogeneity: disease onset spans the complete age range; genetic susceptibility is complex; rates of progression differ markedly, as does insulin secretory capacity; and complication rates, glycemic control, and therapeutic intervention efficacy vary widely. Mechanistic and immunopathological studies typically show considerable patchiness across subjects, undermining conclusions regarding disease pathways. Without better understanding, type 1 diabetes heterogeneity represents a major barrier both to deciphering pathogenesis and to the translational effort of designing, conducting, and interpreting clinical trials of disease-modifying agents. This realization comes during a period of unprecedented change in clinical medicine, with increasing emphasis on greater individualization and precision. For complex disorders such as type 1 diabetes, the option of maintaining the “single disease” approach appears untenable, as does the notion of individualizing each single patient’s care, obliging us to conceptualize type 1 diabetes less in terms of phenotypes (observable characteristics) and more in terms of disease endotypes (underlying biological mechanisms). Here, we provide our view on an approach to dissect heterogeneity in type 1 diabetes. Using lessons from other diseases and the data gathered to date, we aim to delineate a roadmap through which the field can incorporate the endotype concept into laboratory and clinical practice. We predict that such an effort will accelerate the implementation of precision medicine and has the potential for impact on our approach to translational research, trial design, and clinical management.

Type 1 diabetes is a T cell-mediated autoimmune disease, and insulin is an important target of the autoimmune response associated with β cell destruction. The mechanism of destruction is still unknown. Here, we provide evidence for CD8 T cell autoreactivity associated with recurrent autoimmunity and loss of β cell function in type 1 diabetic islet transplant recipients. We first identified an insulin B chain peptide (insB10-18) with extraordinary binding affinity to HLA-A2(*0201) that is expressed by the majority of type 1 diabetes patients. We next demonstrated that this peptide is naturally processed by both constitutive and immuno proteasomes and translocated to the endoplasmic reticulum by the peptide transporter TAP1 to allow binding to HLA-A2 in the endoplasmic reticulum and cell surface presentation. Peripheral blood mononuclear cells from a healthy donor were primedin vitrowith this peptide, and CD8 T cells were isolated that specifically recognize target cells expressing the insulin B chain peptide. HLA-A2^insB10-18tetramer staining revealed a strong association between detection of autoreactive CD8 T cells and recurrent autoimmunity after islet transplantation and graft failure in type 1 diabetic patients. We demonstrate that CD8 T cell autoreactivity is associated with β cell destruction in type 1 diabetes in humans.

OBJECTIVE: Type 1 diabetes results from selective T-cell–mediated destruction of the insulin-producing β-cells in the pancreas. In this process, islet epitope–specific CD8+ T-cells play a pivotal role. Thus, monitoring of multiple islet–specific CD8+ T-cells may prove to be valuable for measuring disease activity, progression, and intervention. Yet, conventional detection techniques (ELISPOT and HLA tetramers) require many cells and are relatively insensitive.RESEARCH DESIGN AND METHODS: Here, we used a combinatorial quantum dot major histocompatibility complex multimer technique to simultaneously monitor the presence of HLA-A2 restricted insulin B10–18, prepro-insulin (PPI)15–24, islet antigen (IA)-2797–805, GAD65114–123, islet-specific glucose-6-phosphatase catalytic subunit–related protein (IGRP)265–273, and prepro islet amyloid polypeptide (ppIAPP)5–13–specific CD8+ T-cells in recent-onset diabetic patients, their siblings, healthy control subjects, and islet cell transplantation recipients.RESULTS: Using this kit, islet autoreactive CD8+ T-cells recognizing insulin B10–18, IA-2797–805, and IGRP265–273 were shown to be frequently detectable in recent-onset diabetic patients but rarely in healthy control subjects; PPI15–24 proved to be the most sensitive epitope. Applying the “Diab-Q-kit” to samples of islet cell transplantation recipients allowed detection of changes of autoreactive T-cell frequencies against multiple islet cell–derived epitopes that were associated with disease activity and correlated with clinical outcome.CONCLUSIONS: A kit was developed that allows simultaneous detection of CD8+ T-cells reactive to multiple HLA-A2–restricted β-cell epitopes requiring limited amounts of blood, without a need for in vitro culture, that is applicable on stored blood samples.