OBJECTIVETo investigate if recurrent autoimmunity explained hyperglycemia and C-peptide loss in three immunosuppressed simultaneous pancreas-kidney (SPK) transplant recipients.RESEARCH DESIGN AND METHODSWe monitored autoantibodies and autoreactive T-cells (using tetramers) and performed biopsy. The function of autoreactive T-cells was studied with in vitro and in vivo assays.RESULTSAutoantibodies were present pretransplant and persisted on follow-up in one patient. They appeared years after transplantation but before the development of hyperglycemia in the remaining patients. Pancreas transplant biopsies were taken within ∼1 year from hyperglycemia recurrence and revealed β-cell loss and insulitis. We studied autoreactive T-cells from the time of biopsy and repeatedly demonstrated their presence on further follow-up, together with autoantibodies. Treatment with T-cell–directed therapies (thymoglobulin and daclizumab, all patients), alone or with the addition of B-cell–directed therapy (rituximab, two patients), nonspecifically depleted T-cells and was associated with C-peptide secretion for >1 year. Autoreactive T-cells with the same autoantigen specificity and conserved T-cell receptor later reappeared with further C-peptide loss over the next 2 years. Purified autoreactive CD4 T-cells from two patients were cotransplanted with HLA-mismatched human islets into immunodeficient mice. Grafts showed β-cell loss in mice receiving autoreactive T-cells but not control T-cells.CONCLUSIONSWe demonstrate the cardinal features of recurrent autoimmunity in three such patients, including the reappearance of CD4 T-cells capable of mediating β-cell destruction. Markers of autoimmunity can help diagnose this underappreciated cause of graft loss. Immune monitoring during therapy showed that autoimmunity was not resolved by the immunosuppressive agents used.

Low-dose interleukin-2 (IL-2) inhibited unwanted immune responses in several clinical settings and is currently being tested in patients with type 1 diabetes (T1D). Low-dose IL-2 selectively targets regulatory T cells (Tregs), but the mechanisms underlying this selectivity are poorly understood. We show that IL-2–dependent STAT5 activation in Tregs from healthy individuals and patients with T1D occurred at an ∼10-fold lower concentration of IL-2 than that required by T memory (TM) cells or by in vitro–activated T cells. This selective Treg responsiveness is explained by their higher expression of IL-2 receptor subunit α (IL-2Rα) and γ chain and also endogenous serine/threonine phosphatase protein phosphates 1 and/or 2A activity. Genome-wide profiling identified an IL-2–dependent transcriptome in human Tregs. Quantitative assessment of selected targets indicated that most were optimally activated by a 100-fold lower concentration of IL-2 in Tregs versus CD4+ TM cells. Two such targets were selectively increased in Tregs from T1D patients undergoing low-dose IL-2 therapy. Thus, human Tregs possess an IL-2–dependent transcriptional amplification mechanism that widens their selective responses to low IL-2. Our findings support a model where low-dose IL-2 selectively activates Tregs to broadly induce their IL-2/IL-2R gene program and provide a molecular underpinning for low-dose IL-2 therapy to enhance Tregs for immune tolerance in T1D.

Aims/hypothesis MicroRNAs (miRNAs) are key regulators of gene expression and novel biomarkers for many diseases. We investigated the hypothesis that serum levels of some miRNAs would be associated with islet autoimmunity and/or progression to type 1 diabetes. Methods We measured levels of 93 miRNAs most commonly detected in serum. This retrospective cohort study included 150 autoantibody-positive and 150 autoantibody-negative family-matched siblings enrolled in the TrialNet Pathway to Prevention Study. This was a young cohort (mean age = 11 years), and most autoantibody-positive relatives were at high risk because they had multiple autoantibodies, with 39/150 (26%, progressors) developing type 1 diabetes within an average 8.7 months of follow-up. We analysed miRNA levels in relation to autoantibody status, future development of diabetes and OGTT C-peptide and glucose indices of disease progression. Results Fifteen miRNAs were differentially expressed when comparing autoantibody-positive/negative siblings (range −2.5 to 1.3-fold). but receiver operating characteristic (ROC) analysis indicated low specificity and sensitivity. Seven additional miRNAs were differentially expressed among autoantibody-positive relatives according to disease progression; ROC returned significant AUC values and identified miRNA cut-off levels associated with an increased risk of disease in both cross-sectional and survival analyses. Levels of several miRNAs showed significant correlations (r 0.22-0.55) with OGTT outcomes. miR-21-3p, miR-29a-3p and miR-424-5p had the most robust associations. Conclusions/interpretation Serum levels of selected miRNAs are associated with disease progression and confer additional risk of the development of type 1 diabetes in young autoantibody-positive relatives. Further studies, including longitudinal assessments, are warranted to further define miRNA biomarkers for prediction of disease risk and progression.

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Patients with type 1 diabetes (T1D) who are recipients of pancreas transplants are believed to rarely develop T1D recurrence in the allograft if effectively immunosuppressed. We evaluated a cohort of 223 recipients of simultaneous pancreas–kidney allografts for T1D recurrence and its risk factors. With long‐term follow‐up, recurrence was observed in approximately 7% of patients. Comparing the therapeutic regimens employed in this cohort over time, lack of induction therapy was associated with recurrence, but this occurs even with the current regimen, which includes induction; there was no influence of maintenance regimens. Longitudinal testing for T1D‐associated autoantibodies identified autoantibody positivity, number of autoantibodies, and autoantibody conversion after transplantation as critical risk factors. Autoantibodies to the zinc transporter 8 had the strongest and closest temporal association with recurrence, which was not explained by genetically encoded amino acid sequence donor–recipient mismatches for this autoantigen. Genetic risk factors included the presence of the T1D‐predisposing HLA‐DR3/DR4 genotype in the recipient and donor–recipient sharing of HLA‐DR alleles, especially HLA‐DR3. Thus, T1D recurrence is not uncommon and is developing in patients treated with current immunosuppression. The risk factors identified in this study can be assessed in the transplant clinic to identify recurrent T1D and may lead to therapeutic advances.