Dissecting the role of CD4+ T cells in autoimmune diabetes through the use of TCR transgenic mice

Enhancement of Cognitive Function by Andrographolide-Loaded Lactose β-Cyclodextrin Nanoparticles: Synthesis, Optimization, and Behavioural Assessment

This study investigates whether Andrographolide-loaded Lactose β-Cyclodextrin (ALN-βCD) nanoparticles enhance cognitive function, particularly spatial learning and memory. The successful conjugation of lactose to β-cyclodextrin was confirmed via 1H NMR spectroscopy, facilitating neuronal cell entry. The solvent evaporation method was used to create the nanoparticles, which were characterised for particle size, PDI, zeta potential, and drug release. The nanoparticles exhibited a size of 247.9 ± 3.2 nm, a PDI of 0.5 ± 0.02, and a zeta potential of 26.8 ± 2.5 mV. FTIR and TEM analyses, along with in vitro drug release and BBB permeability studies, confirmed their stability and efficacy. Behavioural tests, including the Elevated Plus Maze, Y-Maze, Object Recognition, and Locomotor Activity tests, demonstrated significant improvements in memory, motor coordination, and exploration time in the nanoparticle-treated groups. The group treated with ALN-βCD at a dose of 100 mg/kg/p.o. showed superior cognitive performance compared to the group receiving free andrographolides (AG). Biochemical assays indicated a significant reduction in acetylcholinesterase activity and lipid peroxidation, suggesting increased acetylcholine levels and reduced oxidative stress. Histopathological examination showed improved neuronal function without toxicity. The results showed significant improvements (p < 0.001) in memory and cognitive abilities in experimental animals, highlighting the potential of ALN-βCD nanoparticles as a non-invasive treatment for memory loss. These promising findings warrant further exploration through clinical trials.

Selective immunotargeting of diabetogenic CD4 T cells by genetically redirected T cells

The key role played by islet-reactive CD8 and CD4 T cells in type 1 diabetes calls for new immunotherapies that target pathogenic T cells in a selective manner. We previously demonstrated that genetically linking the signalling portion of CD3-ζ onto the C-terminus of β2 -microglobulin and an autoantigenic peptide to its N-terminus converts MHC-I complexes into functional T-cell receptor-specific receptors. CD8 T cells expressing such receptors specifically killed diabetogenic CD8 T cells, blocked T-cell-induced diabetes in immunodeficient NOD.SCID mice and suppressed disease in wild-type NOD mice. Here we describe the immunotargeting of CD4 T cells by chimeric MHC-II receptors. To this end we chose the diabetogenic NOD CD4 T-cell clone BDC2.5, which recognizes the I-A(g7) -bound 1040-31 mimotope. We assembled several constructs encoding I-A(g7) α- and β-chains, the latter carrying mim or hen egg lysozyme peptide as control, each supplemented with CD3-ζ intracellular portion, either with or without its transmembrane domain. Following mRNA co-transfection of reporter B3Z T cells and mouse CD8 and CD4 T cells, these constructs triggered robust activation upon I-A(g7) cross-linking. A BDC2.5 T-cell hybridoma activated B3Z transfectants expressing the mimotope, but not the control peptide, in both configurations. Potent two-way activation was also evident with transgenic BDC2.5 CD4 T cells, but peptide-specific activation required the CD3-ζ transmembrane domain. Chimeric MHC-II/CD3-ζ complexes therefore allow the selective immunotargeting of islet-reactive CD4 T cells, which take part in the pathogenesis of type 1 diabetes.

Effects of metalloporphyrins on reducing inflammation and autoimmunity

SIGNIFICANCE

High levels of reactive oxygen species can facilitate DNA and protein damage beyond the control of endogenous antioxidants, resulting in oxidative stress. Oxidative stress then triggers inflammation, which can lead to pathological conditions. In genetically susceptible individuals, the conglomeration of oxidative stress and inflammation can enhance autoreactive immune cell activation, causing beta-cell destruction in autoimmune type 1 diabetes. As a means of shielding pancreatic islets, manganese porphyrin (MnP) oxidoreductant treatment has been tested in a number of reported studies.

RECENT ADVANCES

MnP affects both innate and adaptive immune cell responses, blocking nuclear factor kappa-B activation, proinflammatory cytokine secretion, and T helper 1 T-cell responses. As a result, MnP treatment protects against type 1 diabetes onset in nonobese diabetic mice and stabilizes islets for cellular transplantation.

CRITICAL ISSUES

MnP displays global immunosuppressive properties, exemplified by decreased cytokine production from all T-helper cell subsets. This quality may impact infection control in the setting of autoimmunity. Nonetheless, because of their cytoprotective and immunomodulatory function, MnPs should be considered as a safer alternative to other clinical immunosuppressive agents (i.e., rapamycin) for transplantation.

FUTURE DIRECTIONS

Although MnP likely affects only redox-sensitive targets, the mechanism behind global T-cell immunosuppression and the outcome on infection clearance will have to be elucidated. Based on the increased primary engraftment seen with MnP use, protection against primary nonfunction in porcine to human xenotransplants would likely be enhanced. Further, a better understanding of MnP oxidoreductase function may allow for its use in other chronic inflammatory conditions.

Type 1 diabetes: primary antigen/peptide/register/trimolecular complex

Type 1A diabetes (autoimmune) is now immunologically predictable in man, but preventable only in animal models. What triggers the development of autoimmunity in genetically susceptible individuals remains unknown. Studies of non-obese diabetic (NOD) mice reveal that interactions between T-cell receptors of diabetogenic T cell and an MHC class II loaded with an autoantigen are key determinates of the disease. With insulin as the primary target in the NOD mouse, likely man, and possibly the RT1-U rat models, therapeutic targeting of the components of these anti-insulin trimolecular complexes we believe provide a fulcrum for development of preventive therapy. In particular for the NOD mouse model, there is extensive evidence that the dominant insulin peptide driving disease initiation is insulin B chain amino acids 9-23 (SHLVEALYLVCGERG) recognized predominantly by germ-line sequences of a specific T-cell receptor Valpha (TRAV5D-4), and small molecules or monoclonal antibodies directed at this recognition complex can prevent diabetes.

Oxidative stress and redox modulation potential in type 1 diabetes

Redox reactions are imperative to preserving cellular metabolism yet must be strictly regulated. Imbalances between reactive oxygen species (ROS) and antioxidants can initiate oxidative stress, which without proper resolve, can manifest into disease. In type 1 diabetes (T1D), T-cell-mediated autoimmune destruction of pancreatic β-cells is secondary to the primary invasion of macrophages and dendritic cells (DCs) into the islets. Macrophages/DCs, however, are activated by intercellular ROS from resident pancreatic phagocytes and intracellular ROS formed after receptor-ligand interactions via redox-dependent transcription factors such as NF-κB. Activated macrophages/DCs ferry β-cell antigens specifically to pancreatic lymph nodes, where they trigger reactive T cells through synapse formation and secretion of proinflammatory cytokines and more ROS. ROS generation, therefore, is pivotal in formulating both innate and adaptive immune responses accountable for islet cell autoimmunity. The importance of ROS/oxidative stress as well as potential for redox modulation in the context of T1D will be discussed.

Characterization of the KRN cell transfer model of rheumatoid arthritis (KRN-CTM), a chronic yet synchronized version of the K/BxN mouse

In this study, a chronic yet synchronized version of the K/BxN mouse, the KRN-cell transfer model (KRN-CTM), was developed and extensively characterized. The transfer of purified splenic KRN T cells into T cell-deficient B6.TCR.Calpha(-/-)H-2(b/g7) mice induced anti-glucose 6-phosphate isomerase antibody-dependent chronic arthritis in 100% of the mice with uniform onset of disease 7 days after T cell transfer. Cellular infiltrations were assessed by whole-ankle transcript microarray, cytokine and chemokine levels, and microscopic and immunohistochemical analyses 7 through 42 days after T cell transfer. Transcripts identified an influx of monocytes/macrophages and neutrophils into the ankles and identified temporal progression of cartilage damage and bone resorption. In both serum and ankle tissue there was a significant elevation in interleukin-6, whereas macrophage inflammatory protein-1 alpha and monocyte chemotactic protein-1 were only elevated in tissue. Microscopic and immunohistochemical analyses revealed a time course for edema, synovial hypertrophy and hyperplasia, infiltration of F4/80-positive monocytes/macrophages and myeloperoxidase-positive neutrophils, destruction of articular cartilage, pannus invasion, bone resorption, extra-articular fibroplasia, and joint ankylosis. The KRN cell transfer model replicates many features of chronic rheumatoid arthritis in humans in a synchronized manner and lends itself to manipulation of adoptively transferred T cells and characterizing specific genes and T cell subsets responsible for rheumatoid arthritis pathogenesis and progression.

Cutting edge: merocytic dendritic cells break T cell tolerance to beta cell antigens in nonobese diabetic mouse diabetes

In type 1 diabetes, the breach of central and peripheral tolerance results in autoreactive T cells that destroy insulin-producing, pancreatic beta cells. In this study, we identify a critical subpopulation of dendritic cells responsible for mediating both the cross-presentation of islet Ags to CD8(+) T cells and the direct presentation of beta cell Ags to CD4(+) T cells. These cells, termed merocytic dendritic cells (mcDCs), are more numerous in the NOD mouse and, when Ag-loaded, rescue CD8(+) T cells from peripheral anergy and deletion while stimulating islet-reactive CD4(+) T cells. When purified from the pancreatic lymph nodes of overtly diabetic NOD mice, mcDCs break peripheral T cell tolerance to beta cells in vivo and induce rapid onset type 1 diabetes in the young NOD mouse. Thus, the mcDC subset appears to represent the long-sought APC responsible for breaking peripheral tolerance to beta cell Ags in vivo.

IFN-gamma-dependent regulatory circuits in immune inflammation highlighted in diabetes

We demonstrate diverse roles of IFN-gamma in the induction and regulation of immune-mediated inflammation using a transfer model of autoimmune diabetes. The diabetogenic CD4(+)BDC2.5 (BDC) T cell clone upon transfer into NOD.scid mice induced destruction of islets of Langerhans leading to diabetes. Administration of a neutralizing Ab to IFN-gamma (H22) resulted in long-term protection (LTP) from diabetes, with inflammation but persistence of a significant, albeit decreased, number of beta cells. BDC T cells were a mixture of cells expressing high, intermediate, and low levels of the TCR. Clonotype(low) BDC T cells were required for LTP. Furthermore, islet-infiltrating leukocytes in the LTP mice contained Foxp3(+)CD4 T cells. Islet inflammation in both diabetic and LTP mice was characterized by heavy infiltration of macrophages. Gene expression profiles indicated that macrophages in diabetic mice were M1 type, while LTP mice contained M2 differentiated. The LTP was abolished if mice were treated with either Ab-depleting CD4 T cells or a neutralizing Ab to CTLA-4, in this case, only at a late stage. Neutralization of IL-10, TGF-beta, glucocorticoid-induced TNF receptor (GITR), or CD25 had no effect. Transfer of only clonotype(high)-expressing BDC T cells induced diabetes; in contrast, H22 Abs did not inhibit diabetes. While clonotype(high) T cells induced diabetes even when IFN-gamma was neutralized, paradoxically there was reduced inflammation and no diabetes if host myeloid cells lacked IFN-gamma receptor. Hence, using monoclonal CD4 T cells, IFN-gamma can have a wide diversity of roles, depending on the setting of the immune process.

Distinct local immunogenic stimuli dictate differential requirements for CD4+ and CD8+ T cell subsets in the pathogenesis of spontaneous autoimmune diabetes

The strong MHC class II association in human as well as murine Type 1 diabetes (T1D) suggests a central role for CD4+T cells in the disease pathogenesis. Nonetheless, CD8+T cells also play a role in the pathogenic process. We describe how CD4+ or CD8+T cells can contribute differentially to the pathogenesis of T1D using the HLA-DQ8 transgenic mouse models. HLA-DQ8 transgenic mice expressing the costimulatory molecule, B7.1 (RIP.B7.1), or the proinflammatory cytokine, TNF-alpha (RIP.TNF) or both (RIP.B7.RIP.TNF) under the control of rat insulin promoter (RIP) were used. Our observations indicate that in the RIP-B7 model, CD4+T cells were absolutely required for diabetes to occur. However, when CD8+ T cells were also present, the incidence of diabetes increased. On the other hand, in the RIP-TNF model, CD8+T cells were absolutely required for diabetes to occur. Interestingly, when CD4+T cells were also present, the incidence of diabetes decreased. In the RIP-B7.RIP-TNF double transgenic mouse model, either CD4+ or CD8+T cells were sufficient to precipitate diabetes in 100% of the animals. Thus, the relative roles of CD4+ or CD8+T cells in the pathogenesis of T1D are possibly determined by the local inflammatory stimuli.

Genome-wide microarray expression analysis of CD4+ T Cells from nonobese diabetic congenic mice identifies Cd55 (Daf1) and Acadl as candidate genes for type 1 diabetes

NOD.Idd3/5 congenic mice have insulin-dependent diabetes (Idd) regions on chromosomes 1 (Idd5) and 3 (Idd3) derived from the nondiabetic strains B10 and B6, respectively. NOD.Idd3/5 mice are almost completely protected from type 1 diabetes (T1D) but the genes within Idd3 and Idd5 responsible for the disease-altering phenotype have been only partially characterized. To test the hypothesis that candidate Idd genes can be identified by differential gene expression between activated CD4+ T cells from the diabetes-susceptible NOD strain and the diabetes-resistant NOD.Idd3/5 congenic strain, genome-wide microarray expression analysis was performed using an empirical Bayes method. Remarkably, 16 of the 20 most differentially expressed genes were located in the introgressed regions on chromosomes 1 and 3, validating our initial hypothesis. The two genes with the greatest differential RNA expression on chromosome 1 were those encoding decay-accelerating factor (DAF, also known as CD55) and acyl-coenzyme A dehydrogenase, long chain, which are located in the Idd5.4 and Idd5.3 regions, respectively. Neither gene has been implicated previously in the pathogenesis of T1D. In the case of DAF, differential expression of mRNA was extended to the protein level; NOD CD4+ T cells expressed higher levels of cell surface DAF compared with NOD.Idd3/5 CD4+ T cells following activation with anti-CD3 and -CD28. DAF up-regulation was IL-4 dependent and blocked under Th1 conditions. These results validate the approach of using congenic mice together with genome-wide analysis of tissue-specific gene expression to identify novel candidate genes in T1D.

The Countervailing Actions of Myeloid and Plasmacytoid Dendritic Cells Control Autoimmune Diabetes in the Nonobese Diabetic Mouse

Islet Ag-specific CD4(+) T cells receive antigenic stimulation from MHC class II-expressing APCs. Herein, we delineate the direct in vivo necessity for distinct subsets of macrophages and dendritic cells (DC) in type 1 diabetes mellitus of the NOD mouse by using diphtheria toxin-mediated cell ablation. The ablation of macrophages had no impact on islet Ag presentation or on the induction of insulitis or diabetes in either transfer or spontaneous models. However, the ablation of CD11b(+)CD11c(+) DC led to the loss of T cell activation, insulitis, and diabetes mediated by CD4(+) T cells. When the specific myeloid DC subset was "added-back" to mice lacking total DC, insulitis and diabetes were restored. Interestingly, when NOD mice were allowed to progress to the insulitis phase, the ablation of DC led to accelerated insulitis. This accelerated insulitis was mediated by the loss of plasmacytoid DC (pDC). When pDC were returned to depleted mice, the localized regulation of insulitis was restored. The loss of pDC in the pancreas itself was accompanied by the localized loss of IDO and the acceleration of insulitis. Thus, CD11c(+)CD11b(+) DC and pDC have countervailing actions in NOD diabetes, with myeloid DC providing critical antigenic stimulation to naive CD4(+) T cells and pDC providing regulatory control of CD4(+) T cell function in the target tissue.

In CD4+ T-cell-induced diabetes, macrophages are the final effector cells that mediate islet beta-cell killing: studies from an acute model

To understand better how diabetogenic CD4+ T cells induce islet beta-cell death and cause diabetes, a transfer model of acute diabetes using the diabetogenic CD4+ BDC2.5 T-cell clone was established. Transfer of activated BDC T cells into NOD.scid mice resulted in diabetes within a week, characterized by strong inflammatory reaction. Electron micrographs of pancreas depicted macrophages in close contact with beta cells that exhibited signs of apoptosis. Transfer into irradiated recipients inhibited inflammation and the development of diabetes, demonstrating an obligatory role for leukocytes. Selective depletion of neutrophils or natural killer cells had no effect on diabetes induced by BDC2.5 T cells. In contrast, in vivo depletion of phagocytic cells by injection of liposomes containing clodronate abolished diabetes, although inflammation remained present and was characterized mainly by neutrophil infiltration. Treatment with clodronate-liposomes did not affect the antigen-presenting cells within the pancreas. Last, activated macrophages isolated from infiltrated pancreas exhibited cytolytic activity toward primary islet beta cells. Taken together, these results demonstrate that activated macrophages are the key cells mediating islet beta-cell death induced by activated CD4+ T cells.

Control of Type 1 Autoimmune Diabetes by Naturally Occurring CD4+CD25+Regulatory T Lymphocytes in Neonatal NOD Mice

Nonobese diabetic (NOD) mice serve as a model of spontaneous type 1 diabetes (T1D), a T cell-mediated autoimmune disease leading to the destruction of pancreatic insulin-producing beta islet cells. A possible deficiency in regulatory T (T(reg)) cell development or function may promote the activation, expansion, and recruitment of autoreactive T cells and the onset of T1D. Naturally occurring CD4(+)CD25(+) T(reg) (nT(reg)) cells, which typically display potent inhibitory effects on T cell functions in vitro and in vivo, may be defective at controlling autoimmunity in T1D. We have examined the relative contribution of CD4(+)CD25(+) nT(reg) cells in the immune regulation of T1D in the NOD mouse model. CD4(+)CD25(+) T cells represent 5-10% of CD4(+) thymocytes or peripheral T cells from prediabetic neonatal NOD mice, are anergic to TCR signals, and potently suppress activated T cells in a contact-dependent and cytokine-independent fashion in vitro. Unlike total CD4(+) T cells, prediabetic CD25(+)-depleted CD4(+) T cells are potently diabetogenic when transferred in immunodeficient NOD mice. Co-transfer of CD4(+)CD25(+) T cells from thymocytes or peripheral lymphoid tissues of neonatal NOD mice dramatically halts disease development and beta-islet cell lymphocytic infiltration, even when T1D is induced by CD4(+) T cells from BDC2.5 transgenic or diabetic NOD mice. Finally, we show that CD4(+)CD25(+) T(reg) preferentially accumulate in inflamed pancreatic environments, where they potently inhibit the antigen-specific expansion and cytokine effector functions of diabetogenic T cells. Thus, CD4(+)CD25(+) T cell-mediated regulation is operative in the prediabetic neonatal T cell repertoire and can suppress the diabetogenic process and control the onset of T1D.

Induction of allergic inflammation by interleukin-18 in experimental animal models

Interleukin-18 (IL-18) has been regarded as a proinflammatory cytokine because of its potent interferon-gamma-inducing activity. However, mutant mice that release excess amounts of IL-18 spontaneously develop pruritic chronic dermatitis-like atopic dermatitis (AD), suggesting the importance of IL-18 for the development of AD. Intriguingly, depletion of il-18 but not stat6, an essential transcriptional factor for IL-4 signaling, rescues the mice from AD, indicating IL-18-dependent, T-helper 2 (Th2) cell-independent AD. This type of AD is classified as innate-type allergy in contrast to Th2 cell-dependent ordinary allergy. Consistent with the previous studies, mice transferred with antigen-specific Th1 cells exhibit no airway hyperresponsiveness and respiratory eosinophilic inflammation after challenge with antigen alone. However, they suffer from asthma upon challenge with antigen plus IL-18, with comparable levels of both the alterations as in those transferred with Th2 cells following challenge with antigen. The former type of asthma is categorized as Th1-associated allergy. Therefore, it is definitely necessary to evaluate whether individual allergic disorders involve either of these IL-18-mediated pathways or a Th2-mediated one.

Alpha L-integrin I domain cyclic peptide antagonist selectively inhibits T cell adhesion to pancreatic islet microvascular endothelium

Insulitis is a hallmark feature of autoimmune diabetes that ultimately results in islet beta-cell destruction. We examined integrin requirements and specific inhibition of integrin structure in T cell and monocyte adhesion to pancreatic islet endothelium. Examination of cell surface integrin expression on WEHI 7.1 T cells revealed prominent expression of beta-, beta(1)-, alpha(L)-integrins, and low expression of alpha(M)-integrins; whereas WEHI 274.1 monocytes showed significant staining for beta(2)-, beta(1)-, alpha(M)-molecules and no expression of alpha(L)-molecules. Unstimulated islet endothelium showed constitutive levels of ICAM-1 counter-ligand expression with minimal VCAM-1 expression; however, TNF-alpha stimulation increased cell surface density of both molecules. TNF-alpha increased T cell and monocyte rolling and adhesion under hydrodynamic flow conditions. Administration of a cyclic peptide competitor for the alpha(L)-integrin I domain binding sites (cyclo1,12-PenITDGEATDSGC) blocked T cell adhesion without inhibiting monocyte adhesion. Examination of T cell rolling revealed that cLAB.L treatment increased the average rolling velocity on activated endothelium and significantly decreased the fraction of T cells rolling at < or =50 microm/s, suggesting that cLAB.L treatment interferes with signal activation events required for the conversion of T cell rolling to firm adhesion. These data demonstrate for the first time that cyclic peptide antagonists against alpha(L)-integrin I domain attenuate T cell recruitment to islet endothelium.

Pathogenic T-cell clones in autoimmune diabetes: more lessons from the NOD mouse

T-cell clones that can efficiently transfer diabetes to prediabetic nonobese diabetic (NOD) mice provide a powerful approach to dissecting the autoimmune disease process and for investigating immunoregulation. Diabetogenic T-cell clones carried in culture allow for detailed analysis of T-cell effector function and in vivo activity, and thus the contribution of a single clonotype to pathogenesis can be studied. As T cells comprising most or all of the repertoire in T-cell receptor transgenic (TCR-Tg) mice, diabetogenic T-cell clones have led to new variations on the NOD mouse model of autoimmune disease. T-cell clones are being used to screen peptide libraries and proteomic arrays to identify the autoantigens that drive these clones in vivo and to extend our knowledge of the processes that give rise to these antigens. With the identification of peptide agonists and natural ligands, the development of MHC-peptide multimers has been possible. These reagents can track T cells in vivo and thus provide new approaches for disease diagnosis and therapy as well as a versatile set of tools for basic research on how T cells contribute to autoimmune disease.

Diabetes incidence is unaltered in glutamate decarboxylase 65-specific TCR retrogenic nonobese diabetic mice: generation by retroviral-mediated stem cell gene transfer

TCR transgenic mice are valuable tools for dissecting the role of autoantigen-specific T cells in the pathogenesis of type 1 diabetes but are time-consuming to generate and backcross onto congenic strains. To circumvent these limitations, we developed a new approach to rapidly generate mice expressing TCR using retroviral-mediated stem cell gene transfer and a novel picornavirus-like 2A peptide to link the TCR alpha- and beta-chains in a single retroviral vector. We refer to these as retrogenic (Rg) mice to avoid confusion with conventional transgenic mice. Our approach was validated by demonstrating that Rg nonobese diabetic (NOD)-scid mice expressing the diabetogenic TCRs, BDC2.5 and 4.1, generate clonotype-positive T cells and develop diabetes. We then expressed three TCR specific for either glutamate decarboxylase (GAD) 206-220 or GAD 524-538 or for hen egg lysozyme 11-25 as a control in NOD, NOD-scid, and B6.H2(g7) mice. Although T cells from these TCR Rg mice responded to their respective Ag in vitro, the GAD-specific T cells exhibited a naive, resting phenotype in vivo. However, T cells from Rg mice challenged with Ag in vivo became activated and developed into memory cells. Neither of the GAD-reactive TCR accelerated or protected mice from diabetes, nor did activated T cells transfer or protect against diabetes in NOD-scid recipients, suggesting that GAD may not be a primary target for diabetogenic T cells. Generation of autoantigen-specific TCR Rg mice represents a powerful approach for the analysis of a wide variety of autoantigens.

TSH receptor expression in orbital tissue and its role in the pathogenesis of Graves' ophthalmopathy

The TSH receptor (TSHr) is the autoantigen responsible for the hyperthyroidism of Graves' disease. Recent studies suggest that this receptor may also be an autoimmune target in Graves' ophthalmopathy (GO) and pretibial dermopathy (PTD). Its involvement in the pathogenesis of these conditions would help to explain the close clinical associations between hyperthyroidism, GO and PTD. TSHr has been shown to be present in normal orbital and dermal tissues and evidence supports the conviction that expression may be increased in tissues involved in GO and PTD. In the setting of Graves' disease, the expression of this antigen in connective tissues throughout the body may lead to systemic, subclinical connective tissue inflammation. Given this background, local or environmental factors such as circulating or local cytokines, gravitational dependency, anatomic constraint of the bony orbit, or trauma, may augment clinical disease involvement within the orbit and pretibial skin. Alternately, locally enhanced expression of this protein at the sites of clinical disease may not be directly involved in pathogenesis, but could be secondary to the ongoing process, and nonetheless important in disease progression.

Loss of tolerance and autoimmunity affecting multiple organs in STAT5A/5B-deficient mice

STAT5 has previously been reported to be dispensable for the maintenance of tolerance in vivo. However, in examining hemopoiesis in mice lacking both isoforms of STAT5, STAT5A, and STAT5B, we noted that a subset of these mice demonstrated dramatic alterations in several bone marrow progenitor populations concomitant with lymphocytic infiltration of the bone marrow. In addition, cellular infiltration affecting the colon, liver, and kidney was observed in these mice. Survival analysis revealed that STAT5A/5B(-/-) mice exhibited early death. The increased mortality and the pathology affecting multiple organs observed in these mice were abrogated on the recombination-activating gene 1(-/-) background. In light of the similarities between STAT5A/5B-deficient mice and mice unable to signal through the IL-2R, we hypothesized that the tolerizing role of STAT5A/5B was triggered via activation of the IL-2R. In agreement with this, we found that IL-2Rbeta chain-deficient mice exhibited similar hemopoietic abnormalities. Because IL-2 signaling is thought to contribute to tolerance through maintenance of a CD4(+)CD25(+) regulatory T cell population, we examined these cells and observed a numerical reduction in STAT5A/5B(-/-) mice along with a higher rate of apoptosis. These data provide strong evidence for a requirement for STAT5 in the maintenance of tolerance in vivo.

Current perspective on the pathogenesis of Graves' disease and ophthalmopathy

Graves' disease (GD) is a very common autoimmune disorder of the thyroid in which stimulatory antibodies bind to the thyrotropin receptor and activate glandular function, resulting in hyperthyroidism. In addition, some patients with GD develop localized manifestations including ophthalmopathy (GO) and dermopathy. Since the cloning of the receptor cDNA, significant progress has been made in understanding the structure-function relationship of the receptor, which has been discussed in a number of earlier reviews. In this paper, we have focused our discussion on studies related to the molecular mechanisms of the disease pathogenesis and the development of animal models for GD. It has become apparent that multiple factors contribute to the etiology of GD, including host genetic as well as environmental factors. Studies in experimental animals indicate that GD is a slowly progressing disease that involves activation and recruitment of thyrotropin receptor-specific T and B cells. This activation eventually results in the production of stimulatory antibodies that can cause hyperthyroidism. Similarly, significant new insights have been gained in our understanding of GO that occurs in a subset of patients with GD. As in GD, both environmental and genetic factors play important roles in the development of GO. Although a number of putative ocular autoantigens have been identified, their role in the pathogenesis of GO awaits confirmation. Extensive analyses of orbital tissues obtained from patients with GO have provided a clearer understanding of the roles of T and B cells, cytokines and chemokines, and various ocular tissues including ocular muscles and fibroblasts. Equally impressive is the progress made in understanding why connective tissues of the orbit and the skin in GO are singled out for activation and undergo extensive remodeling. Results to date indicate that fibroblasts can act as sentinel cells and initiate lymphocyte recruitment and tissue remodeling. Moreover, these fibroblasts can be readily activated by Ig in the sera of patients with GD, suggesting a central role for them in the pathogenesis. Collectively, recent studies have led to a better understanding of the pathogenesis of GD and GO and have opened up potential new avenues for developing novel treatments for GD and GO.

Beta cells are responsible for CXCR3-mediated T-cell infiltration in insulitis

T cell-mediated loss of insulin-secreting beta cells in the islets of Langerhans is the hallmark of type 1 diabetes. The molecular basis for the directed migration of autoreactive T cells leading to insulitis is presently unknown. Here we demonstrate that in response to inflammation, beta cells secrete the chemokines CXC ligand 10 and CXC ligand 9, which specifically attract T-effector cells via the CXC chemokine receptor 3. In mice deficient for this receptor, the onset of type 1 diabetes is substantially delayed. Thus, in the absence of known etiological agents, CXC receptor 3 represents a novel target for therapeutic interference early in type 1 diabetes.

Interleukin-18 regulates both Th1 and Th2 responses

Although interleukin-18 is structurally homologous to IL-1 and its receptor belongs to the IL-1R/Toll-like receptor (TLR) superfamily, its function is quite different from that of IL-1. IL-18 is produced not only by types of immune cells but also by non-immune cells. In collaboration with IL-12, IL-18 stimulates Th1-mediated immune responses, which play a critical role in the host defense against infection with intracellular microbes through the induction of IFN-gamma. However, the overproduction of IL-12 and IL-18 induces severe inflammatory disorders, suggesting that IL-18 is a potent proinflammatory cytokine that has pathophysiological roles in several inflammatory conditions. IL-18 mRNA is expressed in a wide range of cells including Kupffer cells, macrophages, T cells, B cells, dendritic cells, osteoblasts, keratinocytes, astrocytes, and microglia. Thus, the pathophysiological role of IL-18 has been extensively tested in the organs that contain these cells. Somewhat surprisingly, IL-18 alone can stimulate Th2 cytokine production as well as allergic inflammation. Therefore, the functions of IL-18 in vivo are very heterogeneous and complicated. In principle, IL-18 enhances the IL-12-driven Th1 immune responses, but it can also stimulate Th2 immune responses in the absence of IL-12.

Germ line deletion of the CD1 locus exacerbates diabetes in the NOD mouse

Quantitative and qualitative defects in CD1-restricted natural killer T cells have been reported in several autoimmune-prone strains of mice, including the nonobese diabetic (NOD) mouse. These defects are believed to be associated with the emergence of spontaneous autoimmunity. Here we demonstrate that both CD1d-null NOD and CD1d-null NOD/BDC2.5 T cell receptor transgenic mice have an accelerated onset and increased incidence of diabetes when compared with CD1d(+/-) and CD1d(+/+) littermates. The acceleration of disease did not seem to result from changes in the T helper (Th)1/Th2 balance because lymphocytes purified from lymphoid organs and pancreatic islets of wild-type and CD1d-null mice secreted equivalent amounts of IFN-gamma and IL-4 after stimulation. In contrast, the pancreata of CD1d-null mice harbored significantly higher numbers of activated memory T cells expressing the chemokine receptor CCR4. Notably, the presence of these T cells was associated with immunohistochemical evidence of increased destructive insulitis. Thus, CD1d-restricted T cells are critically important for regulation of the spontaneous disease process in NOD mice.

A key role for ICAM-1 in generating effector cells mediating inflammatory responses

We investigated how the accessory molecule interactions encountered during T cell priming influence T cell-mediated destruction of insulin-producing beta cells and lead to type 1 diabetes. T cell receptor (TCR)-transgenic CD4+ T cells were primed under controlled conditions in vitro before being adoptively transferred into transgenic recipients expressing membrane ovalbumin under the control of the rat insulin promoter (RIP-mOVA). During priming, antigen-presenting cell expression of B7-1 without intracellular adhesion molecule 1 (ICAM-1) led to the generation of effector cells that migrated to the pancreata of RIP-mOVA recipients but did not cause diabetes. In contrast, when T cells were primed with APCs expressing both B7-1 and ICAM-1, pronounced destruction of beta cells and a rapid onset of diabetes were observed. Pathogenicity was associated with T cell production of the macrophage-attracting chemokines CCL3 and CCL4. Thus, interactions of lymphocyte function-associated antigen 1 with ICAM-1 during priming induce both qualitative and quantitative alterations in T effector function and induce potentially autodestructive responses.

Intradermal skin test with diabetes specific antigens in patients with type 1 diabetes

Cell mediated immune response in vitro to a number of antigens has been reported in patients with Type 1 diabetes. The aim of the present study was to develop an in vivo intradermal (delayed type hypersensitivity) skin test using antigens known to be recognized by lymphocytes of patients with Type 1 diabetes and to compare, where possible, the in vivo response to the in vitro T cell proliferation to the same antigens. The skin test was performed in the following group of patients: 55 with recent onset Type 1 diabetes; 16 patients with Type 1 diabetes of longer duration; 10 patients with autoimmune thyroid disease and 20 patients with Latent Autoimmune Diabetes in Adults (LADA). Type 1 diabetes specific antigens for the skin test included glutamic acid decarboxilase (GAD65), insulin and beta casein, whereas diabetes non specific antigens included tetanus toxoid, diphteria, proteus, tubercolin, streptococcus, and glycerol as control. A multitest device consisting of heads delivering intradermally 10 microl of solution containing the antigens was applied to the forearms; the specific antigens were injected in one forearm whereas the non specific antigens were injected in the other forearm. Reading of the reaction, which was considered positive in the presence of a nodule of 2 mm diameter was performed 48 h after the multitest application. The in vitro T cell response to diabetes specific antigens used in the multitest was studied using conventional proliferation assays in patients with recent onset Type 1 diabetes and in age matched normal subjects. Only recent onset Type 1 diabetes patients showed an in vivo positive response to GAD65, such response being detectable in 10 patients (18%). Two patients reacted also to beta casein and insulin, all other patient groups resulted negative but 2 patients with longer duration of Type 1 diabetes. There was no apparent link between the in vivo skin test and in vitro T cell proliferation to GAD65. We conclude that in vivo cell mediated immune reaction to GAD65, insulin and beta casein can be visualized in a minority of patients with recent onset Type 1 diabetes. Further studies are required to determine specificity and whether altering the dose can improve the sensitivity of the test.

The inhibitory effects of transforming growth factor-beta-1 (TGF-beta1) in autoimmune diseases

The importance of transforming growth factor-beta-1 (TGF-beta1) in immunoregulation and tolerance has been increasingly recognized. It is now proposed that there are populations of regulatory T cells (T-reg), some designated T-helper type 3 (Th3), that exert their action primarily by secreting this cytokine. Here, we emphasize the following concepts: (1) TGF-beta1 has multiple suppressive actions on T cells, B cells, macrophages, and other cells, and increased TGF-beta1 production correlates with protection and/or recovery from autoimmune diseases; (2) TGF-beta1 and CTLA-4 are molecules that work together to terminate immune responses; (3) Th0, Th1 and Th2 clones can all secrete TGF-beta1 upon cross-linking of CTLA-4 (the functional significance of this in autoimmune diseases has not been reported, but TGF-beta1-producing regulatory T-cell clones can produce type 1 inflammatory cytokines); (4) TGF-beta1 may play a role in the passage from effector to memory T cells; (5) TGF-beta1 acts with some other inhibitory molecules to maintain a state of tolerance, which is most evident in immunologically privileged sites, but may also be important in other organs; (6) TGF-beta1 is produced by many cell types, is always present in the plasma (in its latent form) and permeates all organs, binding to matrix components and creating a reservoir of this immunosuppressive molecule; and (7) TGF-beta1 downregulates adhesion molecules and inhibits adhesion of leukocytes to endothelial cells. We propose that rather than being passive targets of autoimmunity, tissues and organs actively suppress autoreactive lymphocytes. We review the beneficial effects of administering TGF-beta1 in several autoimmune diseases, and show that it can be effectively administered by a somatic gene therapy approach, which results in depressed inflammatory cytokine production and increased endogenous regulatory cytokine production.