Abstract
Type 1 diabetes (T1D) is an autoimmune disease, in which pancreatic β cells are destroyed in genetically predisposed individuals. While the direct contribution of autoantibodies to the disease pathogenesis is controversial, it is generally recognised that the mechanism of β cell destruction is mediated by autoreactive T cells that had escaped the thymic selection. We aimed to design a method to detect circulating CD8+ T cells autoreactive against an epitope of the glutamic acid decarboxylase autoantigen, isoform 65 (GAD65) ex vivo in T1D patients by using HLA class I tetramers. Low frequencies of GAD65 peptide-specific CD8+ cytotoxic T lymphocytes were detected in peripheral blood lymphocytes (PBMC) of normal controls after GAD65 peptide-specific stimulation. Conversely, their frequencies were significantly higher than in controls in PBMC of T1D patients after GAD65 peptide stimulation. These preliminary data are encouraging in order to develop a reliable assay to be employed in large-scale screening studies.
Highlights
Type 1 diabetes (T1D) is a chronic autoimmune disease where CD4+ and CD8+ T cells recognizing islet autoantigens are likely the mediators of selective destruction of pancreatic islet beta cells [1]
Low frequencies of GAD65 peptide-specific CD8+ cytotoxic T lymphocytes were detected in peripheral blood lymphocytes (PBMC) of normal controls after GAD65 peptide-specific stimulation
Direct demonstration of the prominent role of T cells in the disease progression is provided only in animal models, the preclinical period of the disease in humans is marked by the presence of circulating islet-related autoantibodies to beta cell antigens including insulin, glutamic acid decarboxylase (GAD), isoforms GAD65 and GAD67, the insulinoma-associated antigen (IA2)/tyrosine phosphataselike molecule, IA-2 β or phogrin, and proinsulin [1]
Summary
T1D is a chronic autoimmune disease where CD4+ and CD8+ T cells recognizing islet autoantigens are likely the mediators of selective destruction of pancreatic islet beta cells [1]. Direct demonstration of the prominent role of T cells in the disease progression is provided only in animal models, the preclinical period of the disease in humans is marked by the presence of circulating islet-related autoantibodies to beta cell antigens including insulin, glutamic acid decarboxylase (GAD), isoforms GAD65 and GAD67, the insulinoma-associated antigen (IA2)/tyrosine phosphataselike molecule, IA-2 β or phogrin, and proinsulin [1]. ELISPOT assays were implemented for measuring cell-mediated immune (CMI) responses in T1D [3,4,5] and immunoblot assays [6]. Costimulatory antiCD28 antibodies were shown to enhance autoreactive T cell responses to GAD65 peptides in T1D patients [7], while, in a previous set of experiments, the expansion of the GAD65 (whole molecule) reactive T cells was costimulation dependent in healthy controls, as opposed to T1D patients [8]
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