Dale R. Wegmann

Prime role for an insulin epitope in the development of type 1 diabetes in NOD mice

A fundamental question about the pathogenesis of spontaneous autoimmune diabetes is whether there are primary autoantigens. For type 1 diabetes it is clear that multiple islet molecules are the target of autoimmunity in man and animal models. It is not clear whether any of the target molecules are essential for the destruction of islet beta cells. Here we show that the proinsulin/insulin molecules have a sequence that is a primary target of the autoimmunity that causes diabetes of the non-obese diabetic (NOD) mouse. We created insulin 1 and insulin 2 gene knockouts combined with a mutated proinsulin transgene (in which residue 16 on the B chain was changed to alanine) in NOD mice. This mutation abrogated the T-cell stimulation of a series of the major insulin autoreactive NOD T-cell clones. Female mice with only the altered insulin did not develop insulin autoantibodies, insulitis or autoimmune diabetes, in contrast with mice containing at least one copy of the native insulin gene. We suggest that proinsulin is a primary autoantigen of the NOD mouse, and speculate that organ-restricted autoimmune disorders with marked major histocompatibility complex (MHC) restriction of disease are likely to have specific primary autoantigens.

T-Lymphocyte Clone Specific for Pancreatic Islet Antigen

A cloned T-lymphocyte line, BDC-2.5, was derived from a nonobese diabetic (NOD) mouse and has been found to exhibit specificity for islet cell antigen in vitro and in vivo. This clone is a CD4+ T-lymphocyte that proliferates and makes lymphokine in response to islet cell antigen- and NOD antigen-presenting cells. In an in vivo transplantation system in which islet grafts were made in the presence or absence of the BDC-2.5 T-lymphocytes, it was found that incorporation of the islet-specific T-lymphocytes into the graft site resulted in complete destruction of the transplanted tissue. Similar grafts made with pituitary tissue were not affected by the T-lymphocyte clone. These results suggest that the islet-specific T-lymphocytes mediate islet destruction in a tissue-specific manner.

Diabetogenic T-Cell Clones

The role of T-cells in the pathogenesis of IDDM has been an area of much interest, and investigators have recently acquired new tools for studies on T-cells with the advent of T-cell clones that are reactive with islet antigens. Derived from NOD mice, diabetogenic T-cell lines and clones have for the most part been CD4+ and T-helper 1 (Th1)-like in their cytokine production. Some CD8+ cytotoxic clones have also been reported, although these have generally not transferred diabetes in the absence of CD4+ T-cells. The T-cell clones that have been described can also be separated on the basis of their antigen reactivity. While many of the T-cell lines and clones described react with islets, isolated islet cells, or islet membrane preparations, others have known antigen specificities, reacting with defined islet cell proteins such as insulin, GAD, and heat shock proteins. Particularly in the case of insulin-reactive clones, diabetogenicity has also been demonstrated. In light of the many possible T-cell reactivities that may arise from the islet lesion, the question of whether there is a dominant initiating antigen is a particularly intriguing one.

Role of neutrophils in a mouse model of halothane-induced liver injury

Drug‐induced liver injury (DILI) is a major safety concern in drug development. Its prediction and prevention have been hindered by limited knowledge of the underlying mechanisms, in part the result of a lack of animal models. We developed a mouse model of halothane‐induced liver injury and characterized the mechanisms accounting for tissue damage. Female and male Balb/c, DBA/1, and C57BL/6J mice were injected intraperitoneally with halothane. Serum levels of alanine aminotransferase and histology were evaluated to determine liver injury. Balb/c mice were found to be the most susceptible strain, followed by DBA/1, with no significant hepatotoxicity observed in C57BL/6J mice. Female Balb/c and DBA/1 mice developed more severe liver damage compared with their male counterparts. Bioactivation of halothane occurred similarly in all three strains based on detection of liver proteins adducted by the reactive metabolite. Mechanistic investigations revealed that hepatic message levels of tumor necrosis factor‐α (TNF‐α), interleukin‐1β (IL‐1β); IL‐6, and IL‐8 were significantly higher in halothane‐treated Balb/c mice compared to DBA/1 and C57BL/6J mice. Moreover, a higher number of neutrophils were recruited into the liver of Balb/c mice upon halothane treatment compared with DBA/1, with no obvious neutrophil infiltration detected in C57BL/6J mice. Neutrophil depletion experiments demonstrated a crucial role for these cells in the development of halothane‐induced liver injury. The halothane‐initiated hepatotoxicity and innate immune response‐mediated escalation of tissue damage are consistent with events that occur in many cases of DILI. In conclusion, our model provides a platform for elucidating strain‐based and gender‐based susceptibility factors in DILI development. (HEPATOLOGY 2006;44:1421–1431.)

Altered immune response to insulin in newly diagnosed compared to insulin-treated diabetic patients and healthy control subjects

Summary Insulin-dependent diabetes mellitus (IDDM) is the result of a T-cell mediated autoimmune beta-cell destruction,which is accompanied by autoantibodies. We analysed the cellular and humoral immune response to insulin and insulin peptides in patients with recent-onset IDDM, IDDM patients treated with insulin, non-diabetic first degree relatives and unrelated control subjects. There were no differences in T-cell reactivity to whole insulin or insulin peptides in general between age-matched groups of IDDM patients, relatives or healthy control subjects. In contrast to investigations in NOD mice, no immunodominant or disease-specific insulin peptide could be identified. Surprisingly, a positive correlation of T-cell responses to insulin with age was noted (p < 0.005). This resulted in an inverse relation of insulin autoantibodies (IAA) and insulin reactive T-cells (p < 0.001) together with the well-described negative correlation of IAA with age. Interestingly, insulin-treated patients differed from age-matched recent-onset IDDM patients: first, simultaneous immune recognition of insulin with T-cells and IAA was only seen in patients treated for 6 months with insulin; second, insulin-treated patients rarely responded to whole insulin; third, they displayed less determinant spreading, and finally, recognition of multiple insulin peptides was not accompanied by crossreactivity to whole insulin. These distinct observations in insulin-treated IDDM patients, together with the inverse correlation between humoral and cellular responses to insulin, may result from activation or modulation of different T-cell subsets, and may be of relevance to insulin therapy trials, in which selective activation of non-destructive T-cell subsets may be a key to successful intervention. [Diabetologia (1997) 40: 564–572]

T-cell reactivity to GAD65 peptide sequences shared with coxsackie virus protein in recent-onset IDDM, post-onset IDDM patients and control subjects

Summary GAD65 is one of the major autoantigens associated with insulin-dependent diabetes mellitus (IDDM). The two peptides p17 and p18 of GAD65 that share sequence similarity with coxsackie virus (amino acid sequence identity: PEVKEK) appeared to be the major determinants of GAD65 recognized preferably by T cells from new-onset IDDM patients and their first degree relatives. In contrast, in our study unrelated control subjects frequently recognized the two GAD peptides (55 %, 16/29), similar to first degree relatives (41 %, 12/29) and IDDM patients post-onset (68 %, 15/22). However, recent-onset IDDM patients, responded less frequently (25 %, 4/16) compared with IDDM patients post-onset (p < 0.03) or unrelated control subjects (borderline significant) confirming previous observations in humans and NOD mice that T-cell reactivity to GADp17/p18 at diabetes onset is decreased. Moreover, this study demonstrated a positive correlation of T-cell proliferation to GAD p17 (amino acid 247–266) and p18 (amino acid 260–279) with simultaneous responses to both peptides in 13 % of all subjects tested (n = 97) (p < 0.001). T-cell proliferation to GAD p17 was higher than to p18 in recent-onset diabetic patients, first degree relatives and unrelated control subjects (p < 0.02, p < 0.004, p < 0.002, respectively). However, in post-onset IDDM patients, the two peptides were recognized equally well. Our results show that T-cell reactivity to GAD65 peptides homologous with coxsackie protein is very frequently observed, but not primarily associated with IDDM. The temporary decline of T-cell proliferation is not associated with the beta-cell destruction process, but with clinical manifestation. The positive correlation of reactivity to the two peptides in the viral motif implicates that PEVKEK is an immunogenic epitope. [Diabetologia (1997) 40: 332–338]

Increased NF‐κB activity in B cells and bone marrow‐derived dendritic cells from NOD mice

Type 1 diabetes results from the breakdown of peripheral tolerance. As regulators of T cell activation, antigen‐presenting cells (APC) modulate peripheral tolerance and hence contribute to theimmune dysregulation characteristic of insulin‐dependent diabetes mellitus (IDDM). We initially observed an increased importance of NOD B cell APC function in a T cell priming assay as compared to non‐autoimmune strains. Consistent with this increased APC function, we found that NF‐κB nuclear translocation is increased in unmanipulated NOD and NOD.B10Sn‐H2b B cells and that, inaddition, NOD B cells are more sensitive to NF‐κB‐activating stimuli. We obtained similar results using NOD bone marrow‐derived dendritic cell (BMDC) cultures. As costimulatory molecules havebeen shown to be NF‐κB responsive, we examined the expression of these markers on NOD APC. Both B cells and BMDC expressed elevated levels of CD80 and CD40. Finally, NOD B cells provided better allostimulation than B cells from non‐autoimmune strains. Therefore, hyperactivation of NF‐κB and increased expression of CD80 and CD40 by NOD B cells and BMDC may be a contributing factor in the selection of effector T cells observed in IDDM.

Insulin autoimmunity: prediction/precipitation/prevention type 1A diabetes

Type 1 diabetes of both the NOD mouse and man is associated with autoimmunity directed against insulin which is the only beta cell specific autoantigen identified to date. One can use autoantibodies to insulin to predict diabetes, use insulin peptides to create insulin autoantibodies, insulitis and diabetes, and use insulin or its peptides in animal models to prevent diabetes. An expanding set of resources are now available for the development and testing in man of therapies to prevent type 1 diabetes, and a number of trials utilizing insulin peptides are now underway.

HLA-DQ8-Associated T Cell Responses to the Diabetes Autoantigen Phogrin (IA-2β) in Human Prediabetes

Susceptibility to type 1A autoimmune diabetes is linked to expression of particular MHC class II molecules, notably HLA-DQ8 in man and the orthologous I-Ag7 in the nonobese diabetic mouse. In the present study, we analyzed two peptide epitopes (peptides 2 and 7) from the diabetes autoantigen phogrin (IA-2β), in the context of their presentation by the I-Ag7 and HLA-DQ8 molecules and their role as potential T cell antigenic epitopes in human diabetes. Both of these peptides are targets of diabetogenic CD4+ T cell clones in the nonobese diabetic mouse. Transgenic mice expressing HLA-DQ8 as the sole class II molecule generated a robust T cell-proliferative response when primed with peptide 2 or peptide 7 in CFA. Analysis of the IL-2 secretion from peptide 2-reactive T cell hybridomas stimulated with alanine-substituted peptides identified three residues that were crucial to the response. Among 41 islet cell Ag-positive prediabetic human subjects, 36.5% showed PBMC-proliferative responses to peptide 7, 17.1% to peptide 2, and 17.1% to both peptides; no response was seen among 20 matched healthy controls. Stratification of the data based upon HLA haplotype suggested that peptide 7 could be presented by at least one HLA-DR molecule in addition to HLA-DQ8, a finding that was supported by blocking studies with monomorphic mAbs. The results indicate that common phogrin peptides are targeted by autoreactive T cells in human and murine type 1A diabetes, and that the responses may in part be associated with the similar peptide-binding specificities of I-Ag7 and HLA-DQ8.

The immune response to islets in experimental diabetes and insulin-dependent diabetes mellitus

Over the past year, a number of important observations have been made in the nonobese diabetic mouse and in clinical insulin-dependent diabetes mellitus concerning the autoimmune response to islets. Assays have advanced to the point where individuals at risk for insulin-dependent diabetes mellitus can be readily identified prior to the onset of symptoms and a number of peptides of proteins expressed by the beta cell have been shown to protect nonobese diabetic mice from developing diabetes. The contributions of CD4+ and CD8+ T cells to beta cell destruction are beginning to be understood and this information will probably be of value in the design of intervention strategies for use in human subjects.