Recurrence of Type 1 Diabetes After Simultaneous Pancreas-Kidney Transplantation, Despite Immunosuppression, Is Associated With Autoantibodies and Pathogenic Autoreactive CD4 T-Cells

OBJECTIVE

To investigate if recurrent autoimmunity explained hyperglycemia and C-peptide loss in three immunosuppressed simultaneous pancreas-kidney (SPK) transplant recipients.

RESEARCH DESIGN AND METHODS

We 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.

RESULTS

Autoantibodies 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.

CONCLUSIONS

We 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.Type 1 diabetes is an autoimmune disease characterized by the lymphocytic infiltration of the pancreatic islets (insulitis), β-cell destruction, and loss of insulin secretion (1). Autoreactive CD4 and CD8 T-cells and autoantibodies to islet cell autoantigens are detected in patients and pre-diabetic subjects, often preceding diabetes onset by months to years. Insulin, GAD (GAD, 65-kDa isoform), the tyrosine-like phosphatase protein IA-2, the islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP), and the recently identified cation efflux transporter ZnT8 are well characterized and commonly targeted autoantigens (2–8).Simultaneous pancreas-kidney (SPK) transplantation from deceased donors restores insulin secretion in patients and corrects end-stage renal disease (9). Immunological failures occur in a minority of transplant recipients and are usually categorized as chronic rejection. Another possible cause of immunological failure is recurrence of type 1 diabetes. This was initially reported a few weeks after transplantation in recipients of the tail of the pancreas from living-related HLA-identical twins or siblings who, because of HLA matching, received either no or reduced immunosuppression (10–13). However, diabetes recurrence was <10% in a large series of recipients of deceased donor grafts given immunosuppression sufficient to prevent rejection (14). Further studies associated islet cell autoantibodies with graft failure (15–19) but lacked biopsy data, and rejection was not excluded. Two SPK recipients had partial evidence for diabetes recurrence (20), including limited biopsy data showing selective β-cell loss and/or insulitis and limited autoantibody data (20). None of these studies assessed autoantigen-specific T-cells in the context of graft loss. Islet autoimmunity is considered rare and is not routinely monitored in SPK recipients. Thus, recurrence of type 1 diabetes in SPK recipients remains incompletely characterized.We investigated whether recurrent islet autoimmunity explained the hyperglycemia and loss of insulin secretion observed in three immunosuppressed SPK recipients in the absence of rejection. The immunological assessment included both retrospective and prospective testing for autoantibodies and prospective testing for autoantigen-specific T-cells. Monitoring was continued on extended follow-up after patients were diagnosed with recurrence of type 1 diabetes and received additional immunotherapy to antagonize the autoimmune process. We also characterized the functional features of the autoreactive T-cells detected in these patients in the context of recurring diabetes, using both in vitro and in vivo experimental assays to test the pathogenic effects of the autoreactive T-cells.