Identification of the β cell antigen targeted by a prevalent population of pathogenic CD8⁺T cells in autoimmune diabetes

Abstract

Type 1 diabetes is an autoimmune disease in which autoreactive T cells attack and destroy the insulin-producing pancreatic ␤ cells. CD8 ؉ T cells are essential for this ␤ cell destruction, yet their specific antigenic targets are largely unknown. Here, we reveal that the autoantigen targeted by a prevalent population of pathogenic CD8 ؉ T cells in nonobese diabetic mice is islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP). Through tetramer technology, IGRP-reactive T cells are readily detected in islets and peripheral blood directly ex vivo. The human IGRP gene maps to a diabetes susceptibility locus, suggesting that IGRP also may be an antigen for pathogenic T cells in human type 1 diabetes and, thus, a new, potential target for diagnostic and therapeutic approaches.T he nonobese diabetic (NOD) mouse is a widely studied model of human type 1 diabetes, an autoimmune disease characterized by inflammation of pancreatic islets (insulitis) followed by T cell-mediated destruction of insulin (INS)-producing ␤ cells (1). Both CD4 ϩ and CD8 ϩ T cells are required for this pathogenic process (1); however, CD8 ϩ T cells appear to be responsible for the initial ␤ cell insult (1-3). Whereas the pathogenicity of B cells and autoantibodies is less clear, the autoantigens currently believed to contribute to autoimmune diabetes pathogenesis in NOD mice and humans all were originally identified based on the presence of specific autoantibodies rather than by T cell recognition (4-6). Little is known of the ␤ cell antigens targeted by the pathogenic CD8 ϩ T cells. Although one study identified an INS peptide as the antigenic target of the majority of islet-infiltrating CD8 ϩ T cells in NOD mice (7), the prevalence of these INS-reactive CD8 ϩ T cells was not confirmed in subsequent studies (8,9).A substantial proportion of ␤ cell-autoreactive CD8 ϩ T cells isolated from NOD islets express a shared T cell receptor ␣ (TCR␣) chain (V␣17-J␣42), suggesting recognition of a common ␤ cell peptide (3, 10). These T cells do not recognize the antigenic INS peptide mentioned above (11,12). The pathogenicity of this prevalent T cell population has been well established through studies of the 8.3 T cell clone (a representative T cell clone of the V␣17-J␣42-expressing T cell population) (13, 14). 8.3-Like T cells are present in the earliest islet infiltrates of NOD mice (3) and undergo avidity maturation as islet inflammation progresses to overt disease (8). At any given time, 8.3-like T cells can constitute up to 30-40% of the islet-associated CD8 ϩ T cells (9). Strikingly, quantification of 8.3-like T cells in peripheral blood predicts diabetes development in individual NOD mice (9), unlike any other single immune indicator identified to date. Although the prevalence and pathogenicity of 8.3-like T cells has been clearly established, the identity of their ligand has remained elusive. Materials and MethodsMice. NOD͞Lt mice were maintained by brother-sister mating. 8.3-TCR␣␤-transgenic NOD mice, designated 8.3-NOD, ha...

Gut barrier disruption by an enteric bacterial pathogen accelerates insulitis in NOD mice

“…8.3 NOD CD8 + T cells recognise an immuno-dominant peptide from IGRP, termed IGRP 206-214 , a protein expressed by pancreatic beta cells, and these cells are representative of a significant fraction of CD8 + T cells in pancreatic islets at the onset of inflammation [23,28,29]. Adoptive transfer of IGRP-specific (islet antigen) CD8 + T cells [26] into infected NOD mice confirmed an increase in the proliferation and activation of these cells in the pancreatic LNs (Fig.…”

N‐terminal flanking residues of a diabetes‐associated GAD65 determinant are necessary for activation of antigen‐specific T cells in diabetes‐resistant mice

“…In NOD mice, several peptides from these autoantigens have been identified as targets of T cell responses. These include GAD65 p524-543 and p246-266 [1, 2], GAD65 p206-220 and p286-300 [3], insulin B chain p9-23 [4,5], proinsulin p24-33 (proinsulin II p48-57) [6],, and insulin-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP) p206-214 [8]. Extensive analysis of TCR BV gene usage and CDR3 sequences have demonstrated that the early islet-infiltrating T cell clonal expansion is restricted to distinct BV families, e.g., BV4 [9], BV2, BV12, BV14 [10], BV13 [11], BV8.2 [12], and BV1 [13].…”

Apportioning Blame: Autoreactive CD4+ and CD8+ T Cells in Type 1 Diabetes

“…For some of these novel autoantigens, there is data suggesting their significant role in the development of T1D, such as the existence of T-cell clones capable of transferring the disease or immunotherapy using antigenic peptides derived from these autoantigens (Table 1). These include islet-specific glusose-6-phosphatase catalytic subunitrelated protein (IGRP), ZnT8 and, interestingly, the neurotropic factor S100beta and the glial fibrillary acidic protein (GFAP) (Gomez-Tourino et al 2010Lieberman et al 2003;Trudeau et al 2003;Winer et al 2003), the latter two being antigens not expressed by the beta cells themselves but by a group of nerve cells surrounding the islets called the peri-islet Schwann cells (pSC) which makes their role in T1D pathogenesis controversial.…”

“…IGRP antigen was first identified as the antigen targeted by a prevalent population of pathogenic CD8 + T cells in NOD mice (Lieberman et al 2003) and also by human T lymphocytes . Its relevance to T1D derives from the fact that in the NOD mice the number of IGRP-specific CD8 + T cells correlate with the future development of clinical disease (Trudeau et al 2003).…”