Evidence for In Vivo Primed and Expanded Autoreactive T Cells as a Specific Feature of Patients with Type 1 Diabetes

Abstract

Identifying β cell autoantigen-reactive T cells that are involved in the pathogenesis of type 1 diabetes has been troublesome for many laboratories. Disease-relevant autoreactive T cells should be in vivo Ag experienced. The aim of this study was to test this hypothesis and then use this principle as a strategy for identifying diabetes-relevant autoreactive T cells. In this study, a CSFE dilution assay was used to detect glutamic acid decarboxylase 65 (GAD65)- and insulin-responsive T cells and HLA-0201*-GAD65114–122 pentamers were used to detect CD8+ GAD-responsive T cells in memory CD45RO+ and naive CD45RO− cell populations from patients with type 1 diabetes and healthy control subjects. T cell proliferative history was evaluated by flow cytometry telomere length measurement. CD4+ and CD8+ T cells specific for GAD65 and insulin were present in patients with type 1 diabetes and control subjects. Within the naive CD45RO− cells, CD4+ and CD8+ T cell responses were similar between patients and controls. Within the memory CD45RO+ cells, CD4+ T cell responses against whole GAD65 and insulin and HLA-0201*-GAD65114–122 pentamer-positive CD8+ T cells were found in patients with type 1 diabetes, but not in control subjects (p < 0.05 for all). Responding cells from the CD45RO+ T cell population had substantially shorter telomere lengths than responding cells from the CD45RO− cell population. Diabetes-specific autoreactive T cells in the circulation have uniquely undergone sustained in vivo proliferation and differentiation into memory T cells. Prior selection of these cells is possible and is a way to identify diabetes-relevant target Ags and epitopes.

Recurrence of autoreactive antigen-specific CD4+ T cells in autoimmune diabetes after pancreas transplantation

“…These maturation characteristics distinguish autoreactive cells in T1D subjects from similar, potentially autoreactive, naïve cells, which are present in normal individuals [11][12][13], and identify potential biomarkers that may correlate with clinical status. Pancreas organ transplantation is offered as a treatment for T1D, particularly in the context of simultaneous kidney transplantation, when treatment with chronic immunosuppression is used to suppress organ rejection.…”

T Cell Autoreactivity in the Transplant Milieu

“…The other is a distinct memory phenotype with characteristic cell surface markers: memory T cells express CD45RO, whereas naïve T cells are positive for CD45RA. For example, PBMC from T1D subjects contain both naïve and memory T cells specific for islet autoantigens, with the majority positive for CD45RO, whereas the reverse is true for healthy individuals, whose autoreactive T cell population is almost exclusively naive (8,9,12). A subsequent study extended this phenotypic characterization through the analysis of Kv1.3, a potassium ion channel expressed in chronically activated memory T cells (13).…”

“…One study evaluated this concept in proliferating memory and naïve GAD65-and insulin-reactive CD4 T cell populations from T1D, autoantibody-positive at-risk and healthy subjects. Cells were first separated into CD45RO + and CD45RO − populations, labeled with a telomere length marker and then stimulated with GAD65, insulin or tetanus toxoid (9). No significant differences were observed between patients and healthy subjects in the CD45RO − response to any of the antigens.…”

Induction of antigen-specific tolerance through hematopoietic stem cell-mediated gene therapy: The future for therapy of autoimmune disease?

“…In humans with T1D effector cells serve as a reliable predictor of disease progression [85,86]. They continue to expand as disease progresses and ultimately form memory populations that persist in longstanding diabetics [87,88], long after β-cell function is lost. Any 'cure' must therefore comprise an approach to terminate such pathogenic effector and memory T-cell responses either to permit tolerance induction [90,91] and may be resistant to regulation [92], conventional immunosuppression [88] and myeloablative conditioning regimens [93][94][95][96].…”