T helper 2 (Th2) T cells induce acute pancreatitis and diabetes in immune-compromised nonobese diabetic (NOD) mice

DNA vaccination encoding glutamic acid decarboxylase can enhance insulitis and diabetes in correlation with a specific Th2/3 CD4 T cell response in non-obese diabetic mice

DNA vaccination encoding beta cell autoantigens has been shown very recently to prevent type I diabetes in non-obese diabetic (NOD) mice. However, DNA vaccination encoding microbial or reporter antigens is known to induce specific long-lasting CD4 Th1 and strong cytolytic CD8 T cell responses. As this immune phenotype is associated strongly with beta cell destruction leading to diabetes, we have chosen to study the effects of plasmids encoding glutamic acid decarboxylase (GAD), a crucial beta cell autoantigen, in female NOD mice that developed a 'moderate' diabetes incidence. In the present study, 3-week-old female NOD mice were vaccinated twice in tibialis muscles with plasmid-DNA encoding 65-kDa GAD or betagalactosidase. In GAD-DNA immunized mice, diabetes cumulative incidence (P < 3.10(-3)) and insulitis (P < 7.10(-3)) increased significantly. Simultaneously, DNA immunization induced GAD-specific CD4 T cells secreting interleukin (IL)-4 (P < 0.05) and transforming growth factor (TGF)-beta (P = 0.03). These cells were detected in spleen and in pancreatic lymph nodes. Furthermore, vaccination produced high amounts of Th2 cytokine-related IgG1 (P < 3.10(-3)) and TGF-beta-related IgG2b to GAD (P = 0.015). Surprisingly, diabetes onset was correlated positively with Th2-related GAD-specific IgG1 (P < 10(-4)) and TGF-beta-related IgG2b (P < 3.10(-3)). Moreover, pancreatic lesions resembled Th2-related allergic inflammation. These results indicate, for the first time, that GAD-DNA vaccination could increase insulitis and diabetes in NOD mice. In addition, our study suggests that Th2/3 cells may have potentiated beta cell injury.

Peptides from common viral and bacterial pathogens can efficiently activate diabetogenic T-cells

Cross-reactivity between an autoantigen and unknown microbial epitopes has been proposed as a molecular mechanism involved in the development of insulin-dependent diabetes (type 1 diabetes). Type 1 diabetes is an autoimmune disease that occurs in humans and the nonobese diabetic (NOD) mouse. BDC2.5 is an islet-specific CD4+ T-cell clone derived from the NOD mouse whose natural target antigen is unknown. A biometrical analysis of screening data from BDC2.5 T-cells and a positional scanning synthetic combinatorial library (PS-SCL) was used to analyze and rank all peptides in public viral and bacterial protein databases and identify potential molecular mimic sequences with predicted reactivity. Selected sequences were synthesized and tested for stimulatory activity with BDC2.5 T-cells. Active peptides were identified, and some of them were also able to stimulate spontaneously activated T-cells derived from young, pre-diabetic NOD mice, indicating that the reactivity of the BDC2.5 T-cell is directed at numerous mouse peptides. Our results provide evidence for their possible role as T-cell ligands involved in the activation of diabetogenic T-cells.

Identification of a novel type 1 diabetes susceptibility gene, T-bet

The gene encoding interferon (IFN)-gamma, IFNG, is known as one of the candidate susceptibility genes for type 1 diabetes. In addition, cytokines, including IFN-gamma, play important roles in the pathogenesis of type 1 diabetes. Therefore, we focused on the Th1-specific T-box transcription factor gene (T-bet), which contributes to the induction of the hallmark Th1 cytokine, IFN-gamma. We first screened for polymorphisms in the T-bet gene and detected two microsatellite repeat polymorphisms located in intron 1 and the 3'- flanking region, and two single nucleotide polymorphisms, including a His33Gln substitution within the coding region. By association studies, the Gln-positive phenotype and (CA)14 allele in 3'-flanking region of T-bet were found to be associated with type 1 diabetes in the Japanese population. Furthermore, Gln33 T-bet showed a significantly higher transcriptional activity of the IFNG gene via a dual luciferase reporter assay. Our study suggests the first evidence of an association between type 1 diabetes and polymorphisms in the T-bet gene, and that variation in T-bet transcriptional activity may play a role in the development of type 1 diabetes, possibly through the effect on IFN-gamma production in Th1 cells.

Spontaneous organ-specific Th2-mediated autoimmunity in TCR transgenic mice

CD4(+) T cells that lead to autoimmune gastritis (AIG) in BALB/c mice are either Th1 or Th2 cells. To test whether the phenotype of disease is related to the particular TCR expressed by the pathogenic cell, we have generated several lines of TCR transgenic mice using receptors cloned from pathogenic Th1 or Th2 cells. We previously described spontaneous inflammatory AIG in A23 mice, caused by the transgenic expression of the TCR from a Th1 clone, TXA23. In this study we describe the generation of A51 mouse lines, transgenic for the TCR of a CD4(+) self-reactive Th2 clone, TXA51. A proportion of A51 mice spontaneously develop AIG by 10 wk of age, with a disease characterized by eosinophilic infiltration of the gastric mucosa and Th2 differentiation of transgenic T cells in the gastric lymph node. The Th2 phenotype of this autoimmune response seems to be related to a low availability of MHC class II-self peptide complexes. This in vivo model of spontaneous Th2-mediated, organ-specific autoimmunity provides a unique example in which the clonotypic TCR conveys the Th2 disease phenotype.

Recruitment of IFN-gamma-producing (Th1-like) cells into the inflamed retina in vivo is preferentially regulated by P-selectin glycoprotein ligand 1:P/E-selectin interactions

Although there is evidence that altering the Th1/Th2 balance toward Th2 cells may be important in the resolution of Th1-type autoimmune disease, adoptive transfer of Th2 cells is not effective in protecting against Th1-type disease and may cause disease. Therefore, we examined the recruitment of Th1- and Th2-like cells into the retina in the murine autoimmune disease experimental autoimmune uveoretinitis. CD4 T cells were polarized in vitro to IFN-gamma-producing Th1-like cells and non-IFN-gamma-producing Th2-like cells, labeled, and adoptively transferred. Trafficking to the retina in vivo was evaluated by scanning laser ophthalmoscopy and infiltration by confocal microscopy. There were more rolling and adherent Th1-like cells and they rolled more slowly than did Th2-like cells. Th1-like cells were preferentially recruited into the retinal parenchyma at both initiation and resolution. Surface P-selectin glycoprotein ligand 1 (PSGL-1) and LFA-1 were up-regulated on both populations but were expressed at higher levels on Th1-like cells. Up-regulation of CD44 expression was higher on Th2-like cells. P-selectin, E-selectin, and ICAM-1 are up-regulated on postcapillary venules in the retina. Pretreatment of Th1-like cells with anti-PSGL-1 inhibited rolling and infiltration of Th1-like cells but not Th2-like cells, providing direct in vivo evidence for the inability of Th2 to respond to P/E-selectin despite increased expression of PSGL-1. Anti-LFA-1 pretreatment inhibited infiltration of both Th1- and Th2-like cells, but more so Th-1. We suggest that random trafficking of activated T cells (both Th1 and Th2) across the blood-retina barrier is mediated by CD44:CD44R and LFA-1:ICAM-1, whereas preferential recruitment of Th1 cells is mediated by PSGL-1:P/E-selectin.

Achieving antigen-specific immune regulation

A study in this issue of the JCI shows that in response to autoantigens consisting of peptides from normal proteins, patients with diabetes mount a T cell response characterized by production of IFN-gamma (see the related article beginning on page 451). However, in response to these same antigens, T cells from normal control subjects produce IL-10. The antigen-specific response characterized by release of a regulatory cytokine suggests a mechanism for the control of autoimmunity that is initiated at the time of antigen presentation.

T-cell receptor transgenic mice in the study of autoimmune diseases

T cell receptor transgenic mice have been a valuable tool in the study of the immune system, from development to selection to tolerance or pathogenesis. In this manuscript we review the T cell receptor transgenic mouse lines with specificity for self antigens that have been reported before August 2003. Many such lines have been generated, which have been instrumental in our understanding of, among other aspects, the role regulatory T cells in preventing autoimmunity, the role of microbes in modifying its outcome, the influence of the genetic background, the importance of regional differences in self-antigen concentration, and the importance of differences in antigen deposition between different tissues.

Effects of deviating the Th2-response in murine mercury-induced autoimmunity towards a Th1-response

T-helper cells type 1 (Th1) and type 2 (Th2) play an important role in the pathogenesis of autoimmune diseases. In many Th1-dependent autoimmune models, treatment with recombinant interleukin-12 (rIL-12) accelerates the autoimmune response. Mercury-induced autoimmunity (HgIA) in mice is an H-2 regulated condition with antinucleolar antibodies targeting fibrillarin (ANoA), systemic immune-complex (IC) deposits and transient polyclonal B-cell activation (PBA). HgIA has many characteristics of a Th2 type of reaction, including a strong increase of IgE, but disease induction is critically dependent on the Th1 cytokine IFN-gamma. The aim of this study was to investigate if a strong deviation of the immune response in HgIA towards Th1 would aggravate HgIA. Injections of both rIL-12 and anti-IL-4 monoclonal antibody (alpha-IL-4) reduced the HgCl2-(Hg-)induced concentration of the Th2-dependent serum IgE and IgG1, but increased the Th1-dependent serum IgG2a. The IgG-ANoA developed earlier and attained a higher titre after combined treatment, and the ANoA titre of the IgG1 isotype decreased while the ANoA titre of the Th1-associated IgG2a, IgG2b and IgG3-ANoA isotypes increased. Treatment with rIL-12 alone increased the Hg-induced IgG2a and IgG3 ANoA titres, the PBA, and the IC deposits in renal and splenic vessel walls, while treatment with alpha-IL-4 + Hg inhibited renal but not splenic vessel wall IC deposits. We conclude that manipulating the cytokine status, by altering the Th1/Th2 balance, will influence autoimmune disease manifestations. This might be an important way of modulating human autoimmune diseases.

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.

Interleukin-10 Gene Promoter Region Polymorphisms in Patients with Type 1 Diabetes and Autoimmune Thyroid Disease

Type 1 diabetes is a heterogeneous autoimmune disease and is frequently associated with other organ-specific autoimmune diseases, including autoimmune thyroid disease (AITD). Type 1 diabetic patients with AITD are known to show distinct clinical and immunological features from patients without AITD. This study investigated whether interleukin-10 (IL-10) gene promoter region polymorphisms are associated with susceptibility to type 1 diabetes and AITD. The frequency of -1082G/A, -819C/T, and -592C/A polymorphisms was analyzed in 54 type 1 diabetic patients with AITD, 74 type 1 diabetic patients without AITD, 124 nondiabetic patients with AITD, and 107 healthy subjects in a case-control study. No significant differences on the allele and genotype frequencies of three polymorphisms were found not only in type 1 diabetic patients with AITD compared with normal controls, but also between nondiabetic patients with AITD and healthy controls. The distribution of IL-10 gene haplotypes was also similar between both patient groups and normal controls. These results suggest that IL-10 gene promoter region polymorphisms are not associated with genetic susceptibility to type 1 diabetes and AITD.

Induction of autoantigen-specific Th2 and Tr1 regulatory T cells and modulation of autoimmune diabetes

Autoantigen-based immunotherapy can modulate autoimmune diabetes, perhaps due to the activation of Ag-specific regulatory T cells. Studies of these regulatory T cells should help us understand their roles in diabetes and aid in designing a more effective immunotherapy. We have used class II MHC tetramers to isolate Ag-specific T cells from nonobese diabetic (NOD) mice and BALB/c mice treated with glutamic acid decarboxylase 65 peptides (p206 and p221). Based on their cytokine secretion profiles, immunization of NOD mice with the same peptide induced different T cell subsets than in BALB/c mice. Treatment of NOD mice induced not only Th2 cells but also IFN-gamma/IL-10-secreting T regulatory type 1 (Tr1) cells. Adoptive transfer experiments showed that isolated tetramer(+) T cells specific for p206 or p221 could inhibit diabetes development. These cells were able to suppress the in vitro proliferation of other NOD mouse T cells without cell-cell contact. They performed their regulatory functions probably by secreting cytokines, and Abs against these cytokines could block their suppressive effect. Interestingly, the presence of both anti-IL-10 and anti-IFN-gamma could enhance the target cell proliferation, suggesting that Tr1 cells play an important role. Further in vivo experiments showed that the tetramer(+) T cells could block diabetogenic T cell migration into lymph nodes. Therefore, treatment of NOD mice with autoantigen could induce Th2 and Tr1 regulatory cells that can suppress the function and/or block the migration of other T cells, including diabetogenic T cells, and inhibit diabetes development.

Paralytic autoimmune myositis develops in nonobese diabetic mice made Th1 cytokine-deficient by expression of an IFN-gamma receptor beta-chain transgene

Nonobese diabetic (NOD) mice and some human type 1 diabetes (T1D) patients manifest low to high levels of other autoimmune pathologies. Skewing their cytokine production from a Th1 (primarily IFN-gamma) to a Th2 (primarily IL-4 and IL-10) pattern is a widely proposed approach to dampen the pathogenicity of autoreactive diabetogenic T cells. However, it is important that altered cytokine balances not enhance any other autoimmune proclivities to dangerous levels. Murine CD4 T cells are characterized by a reciprocal relationship between the production of IFN-gamma and expression of the beta-chain component of its receptor (IFN-gamma RB). Thus, NOD mice constitutively expressing a CD2 promoter-driven IFN-gamma RB transgene in all T cells are Th1-deficient. Unexpectedly, NOD.IFN-gamma RB Tg mice were found to develop a lethal early paralytic syndrome induced by a CD8 T cell-dependent autoimmune-mediated myositis. Furthermore, pancreatic insulitis levels were not diminished in 9-wk-old NOD.IFN-gamma RB Tg females, and overt T1D developed in the few that survived to an older age. Autoimmune-mediated myositis is only occasionally detected in standard NOD mice. Hence, some manipulations diminishing Th1 responses can bring to the forefront what are normally secondary autoimmune pathologies in NOD mice, while also failing to dependably abrogate pancreatic beta cell destruction. This should raise a cautionary note when considering the use of protocols that induce alterations in cytokine balances as a means of blocking progression to overt T1D in at-risk humans.

Th1 and Th2 pancreatic inflammation differentially affects homing of islet-reactive CD4 cells in nonobese diabetic mice

The control of lymphocyte recruitment to the site of inflammation is an important component determining the pathogenicity of an autoimmune response. Progression from insulitis to diabetes in the nonobese diabetic mouse is typically associated with Th1 pancreatic inflammation, whereas Th2 inflammation can seemingly be controlled indefinitely. We show that a Th1 (IFN-gamma) pancreatic environment greatly accelerates the recruitment of adoptively transferred islet-specific CD4 T cells to the islets and also accelerates the onset of diabetes. The increased number of islet-reactive T cells in the pancreas does not result from increased proliferation or a decreased rate of apoptosis; instead, it appears to be caused by a greatly facilitated rate of entry to the pancreas. In contrast, a Th2 (IL-4) pancreatic environment does act to enhance Ag-specific proliferation and decrease the rate of apoptosis in islet-specific CD4 T cells. Nonpathogenic/regulatory cells are not preferentially expanded by the presence of IL-4. Increased recruitment to the islets was also observed in the presence of IL-4, but to a lesser extent than in the presence of IFN-gamma, and this lesser increase in the rate of recruitment did not accelerate diabetes onset within the time period examined. Therefore, the production of Th1 cytokines by initial islet-infiltrating cells may cause a greater increase than Th2 cytokines in the rate of recruitment of activated T cells. This difference in rate of recruitment may be critical in determining whether the initial infiltrate proceeds to diabetes or whether a steady state insulitis develops that can be maintained.

Activation of human T cells by FcR nonbinding anti-CD3 mAb, hOKT3gamma1(Ala-Ala)

Dimeric Fc receptor (FcR) nonbinding anti-CD3 antibodies have been developed to minimize toxicities associated with classical anti-CD3 monoclonal antibodies (e.g., OKT3). Studies with murine analogs of non-FcR-binding antibodies have shown reduced mitogenicity compared to OKT3. In a trial of an FcR nonbinding humanized anti-CD3 mAb hOKT3gamma1(Ala-Ala) for treatment of patients with type 1 diabetes, we found significant increases in IL-10 and IL-5 in the serum of 63% and 72% of patients, respectively, and TNF-alpha and IL-6 levels that were lower than those previously reported following OKT3 therapy. The activation signal delivered by hOKT3gamma1(Ala-Ala) was associated with calcium signaling and cytokine production by previously activated human cells in vitro. However, the production of IL-10, compared to IFN-gamma on a molar basis, was greater after culture with hOKT3gamma1(Ala-Ala) than with OKT3. Flow cytometric studies confirmed that OKT3 induced IFN-gamma and IL-10 production, but hOKT3gamma1(Ala-Ala) induced only detectable IL-10 production in CD45RO(+) cells. Moreover, in vivo, we found IL-10(+)CD4(+) T cells after drug treatment. These cells were heterogeneous but generally CD45RO(+), CTLA-4(-), and expressed CCR4. A subgroup of these cells expressed TGF-beta. Thus, the non-FcR binding anti-CD3 mAb, hOKT3gamma1(Ala-Ala) delivers an activation signal to T cells that is quantitatively and qualitatively different from OKT3. It leads to the generation of T cells that might inhibit the autoimmune response and may be involved in the beneficial effect on beta cell destruction in Type 1 diabetes.

Autoreactive T cells promote post-traumatic healing in the central nervous system

In general, autoimmune responses are considered harmful to the host. In the best-defined model of autoimmune disease, murine experimental allergic encephalomyelitis (EAE), for example, brain-protein-specific autoimmune responses of both major classes, type-1 and type-2, have been implicated in causing brain pathology. We induced type-1 and type-2 autoimmunity to myelin oligodendrocyte protein (MOG) in C57.BL/6 mice. Instead of using pertussis toxin (PTX) to open the blood-brain barrier (BBB), which is the classic procedure, we set an aseptic cerebral injury (ACI) to see what the consequences of pre-primed, autoreactive type-1 and type-2 memory T cells gaining access to the brain in the course of sterile tissue injury would be. Neither of these autoimmune response types induced pathology; on the contrary, both accelerated re-vascularization and post-traumatic healing. The data suggest that induction of either type-1 or type-2 autoimmune responses is not inherently noxious to the host, but can have beneficial effects on tissue repair. Autoimmune pathology may develop only if molecules of microbial origin such as pertussis toxin additionally induce the "infectious nonself/danger" reaction in the antigen-presenting cells (APC) of the target organ itself.

Cytokines: promoters and dampeners of autoimmunity

Cytokines are the co-ordinators of the immune system and, as such, are important targets for immunomodulation. Progress has been made towards the use of IL-10 for immunosuppressive therapy to prevent autoimmunity. Interest has also recently focused on the role of cytokines in controlling the activation of dendritic cells and NK cells, and the consequences of this for the development of autoaggressive responses. Genes involved in IFN-activated pathways that control the survival of lymphocytes have been strongly linked to lupus susceptibility, and IFN-mediated defenses against viral infection have been shown to determine susceptibility to a model of viral-induced diabetes.

Genetic association between interleukin-10 gene promoter region polymorphisms and type 1 diabetes age-at-onset

This study investigated whether interleukin-10 (IL-10) gene promoter region polymorphisms are associated with susceptibility to or clinical presentation of type 1 diabetes. The frequency of -1082G/A, -819C/T, and -592C/A polymorphisms was analyzed in 128 Japanese patients with type 1 diabetes and in 107 healthy control subjects in a case-controlled study. The allelic and haplotypic frequencies of the IL-10 gene promoter region polymorphisms were similar in patients with type 1 diabetes and in control subjects. However, the -819T and -592A allele were associated with adult-onset (>18 years) of the disease (p = 0.037). Furthermore, the frequency of ATA haplotype was increased in adult-onset patients than that in early-onset patients (< or =18 years; p = 0.037). Among the genotypes comprising ATA haplotype, the frequency of ATA/ATA was significantly higher in adult-onset patients than in early-onset patients (p = 0.004). These results suggest that the IL-10 gene promoter polymorphisms are associated with the age-at-onset in Japanese patients with type 1 diabetes.

Asthma: an epidemic of dysregulated immunity

The remarkable increase in asthma prevalence that has occurred over the last two decades is thought to be caused by changes in the environment due to improved hygiene and fewer childhood infections. However, the specific infections that limit T helper type 2 (T(H)2)-biased inflammation and asthma are not fully known. Infectious organisms, including commensal bacteria in the gastrointestinal tract and hepatitis A virus, may normally induce the development of regulatory T (T(R)) cells and protective immunity that limit airway inflammation and promote tolerance to respiratory allergens. In the absence of such infections, T(H)2 cells--which are developmentally related to T(R) cells--develop instead and coordinate the development of asthmatic inflammation.

Cytokine production in Linomide-treated nod mice and the potential role of a Th (1)/Th(2) shift on autoimmune and anti-inflammatory processes

Linomide prevents the development of autoimmune insulitis and insulin-deficient diabetes mellitus in female NOD mice. Linomide prevents development of autoimmune manifestations in other experimentally induced and spontaneous autoimmune diseases as well, but the mechanism of action is unknown. The present report summarizes our investigations on the effect of Linomide on different functional T cell subsets in NOD mice analyzed according to their cytokine profile. Supernatants from cultured splenocytes and peritoneal cells taken from Linomide-treated mice contained lower levels of TNFalpha, IL-1 beta, IFN gamma and IL-12 versus higher levels of IL-4, IL-6 and IL-10 in comparison with supernatants from cultures of untreated mice. Our results suggest that regulation of autoimmunity following oral Linomide administration in NOD mice induces a shift from Th(1) to Th(2) phenotype response, thereby preventing the development of diabetes by active cytokine-induced immunoregulation of T cell subsets, including downregulation of Th(1) and upregulation of Th(2).

Pertussis toxin modulates the immune response to neuroantigens injected in incomplete Freund's adjuvant: induction of Th1 cells and experimental autoimmune encephalomyelitis in the presence of high frequencies of Th2 cells

Pertussis toxin (PT) has been widely used to facilitate the induction of experimental autoimmune encephalomyelitis (EAE) in rodents. It has been suggested that this microbial product promotes EAE by opening up the blood-brain barrier and thereby facilitates the migration of pathogenic T cells to the CNS. However, PT has other biological effects that could contribute to its activity in EAE, such as enhancing the cytokine production by T cells and induction of lymphocytosis. In this work, we investigated the effects of PT on the pathogenicity, cytokine differentiation, and clonal sizes of neuroantigen-reactive T cells in EAE in mice. Our results show that PT prevented the protection from EAE conferred by injection of PLPp139-151 in IFA and induced high frequencies of peptide-specific Th1 cells and disease. Interestingly, the mice developed EAE despite the simultaneous vigorous clonal expansion of PLPp139-151-specific Th2 cells. The data indicate that the Th2 cells in this model neither were protective against EAE nor promoted the disease. Furthermore, the results suggested that the effects of the toxin on neuroantigen-reactive T cells were promoted by the PT-induced activation of APCs in lymphoid tissues and the CNS. Together, the results suggest that microbial products, such as PT, could contribute to the initiation of autoimmune disease by modulating the interaction between the innate and adaptive immune system in the response to self Ags.

The Th1/Th2 cytokine balance changes with the progress of the immunopathological lesion of Sjogren's syndrome

Expression of type-1 and type-2 cytokines at the mRNA level in labial salivary glands (LSG) of patients with Sjogren's syndrome (SS), as reported by several groups, have generated conflicting results. In the present study we have directly examined the production of IL-4, IL-13 and IFN-gamma by lymphocytes infiltrating the LSG of 44 consecutive patients referred for SS evaluation. Cytokines production was evaluated following in vitro culture of LSG in the presence of IL-2. IFN-gamma and IL-13 were detected in the majority of SN (24/44 and 26/44, respectively) while IL-4 was present in 5/44 SN. The presence of IFN-gamma was significantly higher in SS patients, as opposed to patients who did not fulfil the criteria for SS (P < 0.01). In addition, almost all cultured lymphocytes expressed mRNA for IFN-gamma (17/19 cultures) and IL-13 (18/19) while IL-4 mRNA was also expressed at high frequency (14/19 cultures). Interestingly, the IFN-gamma mRNA copies in cultured lymphocytes correlated significantly with the intensity of lymphocytic infiltration as evaluated by Chisholm's score (P < 0.01). Furthermore, RT-PCR of RNA extracted from whole LSG from 14 SS patients also demonstrated the presence of all cytokines in the majority of the cases and the prevalence of IFN-gamma in LSG with high-grade infiltration. Because IL-13 was produced by the majority of the cultured LSG, IgE production was also evaluated. Interestingly, IgE was detected in 21/44 LSG culture SN and mainly in those biopsies that had Chisholm's score less than 0.5 (P < 0.05). We conclude that lymphocytes infiltrating the LSG are capable of producing both Th1 and Th2 cytokines and that the balance between them shifts in favour of Th1 in LSG with high infiltration score and in patients with SS.

Epitope spreading in immune-mediated diseases: implications for immunotherapy

Evidence continues to accumulate supporting the hypothesis that tissue damage during an immune response can lead to the priming of self-reactive T and/or B lymphocytes, regardless of the specificity of the initial insult. This review will focus primarily on epitope spreading at the T-cell level. Understanding the cellular and molecular basis of epitope spreading in various chronic immune-mediated human diseases and their animal models is crucial to understanding the pathogenesis of these diseases and to the ultimate goal of designing antigen-specific treatments.

IL-6 secretion by human pancreatic periacinar myofibroblasts in response to inflammatory mediators

There is increasing evidence that IL-6 plays an important role in the pathophysiology of acute pancreatitis via its broad proinflammatory actions. To identify the local biosynthetic site for IL-6 in human pancreas, we investigated IL-6 secretion in human pancreatic periacinar myofibroblasts. IL-6 secretion was determined by ELISA and Northern blotting. The activation of NF-kappaB was assessed by EMSA. The activation of mitogen-activated protein kinase (MAPK) was assessed by immunoblotting. IL-6 secretion was rapidly induced by IL-17, IL-1beta, and TNF-alpha. EMSAs demonstrated that IL-17, IL-1beta, and TNF-alpha induced NF-kappaB activation within 1.5 h after stimulation, and a blockade of NF-kappaB activation by the pyrrolidine derivative of dithiocarbamate and tosyl-phe-chloromethylketone markedly reduced the IL-17-, IL-1beta-, or TNF-alpha-induced IL-6 gene expression. Furthermore, IL-17, IL-1beta, and TNF-alpha induced a rapid activation of extracellular signal-related kinase p42/44 and p38 MAPKs, and specific MAPK inhibitors (SB203580, PD98059, and U0216) significantly reduced IL-17-, IL-1beta-, or TNF-alpha-induced IL-6 secretion, indicating the role of MAPKs in the induction of IL-6. The combination of either IL-17 plus IL-1beta or IL-17 plus TNF-alpha enhanced IL-6 secretion and IL-6 mRNA expression; in particular, the effects of IL-17 plus TNF-alpha were much stronger than those induced by IL-17 plus IL-1beta. TNF-alpha-induced IL-6 mRNA degraded rapidly at any concentrations, and the combination of IL-17 and TNF-alpha markedly enhanced IL-6 mRNA stability. This indicates that the effects of IL-17 plus TNF-alpha were regulated at the post-transcriptional level. In conclusion, pancreatic periacinar myofibroblasts secreted a large amount of IL-6 in response to proinflammatory cytokines. These cells might play an important role in the pathogenesis of acute pancreatitis via IL-6 secretion.

T helper 1 and T helper 2 cells are pathogenic in an antigen-specific model of colitis

Dysregulated T cell responses to enteric bacteria have been implicated as a common mechanism underlying pathogenesis in rodent models of colitis. However, the bacterial species and T cell specificities that induce disease have been poorly defined. We have developed a model system in which target antigen, bacterial host, and corresponding T cell specificity are defined. OVA-specific T cells from DO11.RAG-2(-/-) TCR transgenic mice were transferred into RAG-2(-/-) recipients whose intestinal tracts were colonized with OVA-expressing or control Escherichia coli. Transfer of antigen-naive DO11.RAG-2(-/-) T cells into recipients colonized with OVA-E. coli resulted in enhanced intestinal recruitment and cell cycling of OVA-specific T cells; however, there was no development of disease. In contrast, transfer of polarized T helper (Th) 1 and Th2 populations resulted in severe wasting and colitis in recipients colonized with OVA-expressing but not control E. coli. The histopathologic features of disease induced by Th1 and Th2 transfers were distinct, but disease severity was comparable. Induction of disease by both Th1 and Th2 transfers was dependent on bacterially associated OVA. These results establish that a single bacterially associated antigen can drive the progression of colitis mediated by both Th1 and Th2 cells and provide a new model for understanding the immunoregulatory interactions between T cells responsive to gut floral antigens.

Understanding autoimmune diabetes: insights from mouse models

Type 1 or insulin-dependent diabetes is an autoimmune disease that causes the selective destruction of insulin-secreting beta cells in the pancreatic islets. Although this is a polygenic disease, with at least 20 genes implicated, the dominant susceptibility locus maps to the major histocompatibility complex (MHC), both in humans and in rodent models. However, in spite of progress on several fronts, the molecular pathology of autoimmune diabetes remains incompletely defined. Major areas of research include environmental trigger factors, the identification and role of beta-cell antigens in inducing and maintaining the autoimmune response, and the nature of the pathogenic and protective lymphocytes involved. In this review, we will focus on these areas to highlight recent advances in understanding the pathogenesis of autoimmune diabetes, drawing extensively on insights gained by studying the non-obese diabetic (NOD) mouse.

The enemy within: keeping self-reactive T cells at bay in the periphery

The remarkable capacity of the mammalian immune system to coordinate deadly attacks against numerous invading pathogens, yet turn a blind eye to self-tissues continues to fascinate immunologists. It has been clear for some time that immune cells capable of recognizing self-proteins exist in normal individuals without seemingly causing harm. The 'peripheral tolerance' mechanisms that keep these cells in check are the focus of intense research, not least because defects in these pathways might cause autoimmune diseases. In this review, new developments in our understanding of peripheral tolerance are discussed.

Plasmid vaccination with insulin B chain prevents autoimmune diabetes in nonobese diabetic mice

The insulin B (InsB) chain bears major type 1 diabetes-associated epitopes of significance for disease in humans and nonobese diabetic (NOD) mice. Somatic expression of InsB chain initiated early in life by plasmid inoculation resulted in substantial protection of female NOD mice against disease. This was associated with a T2 shift in spleen, expansion of IL-4-producing and, to a lesser extent, of IFN-gamma-secreting T cells in pancreatic lymph nodes, as well as intermolecular Th2 epitope spreading to glutamic acid decarboxylase determinants. A critical role of IL-4 for the Ag-specific protective effect triggered by plasmid administration was revealed in female IL-4(-/-) NOD mice that developed diabetes and higher Th1 responses. Coadministration of IL-4-expressing plasmid or extension of the vaccination schedule corrected the unfavorable response of male NOD mice to DNA vaccination with InsB chain. Thus, plasmid-mediated expression of the InsB chain early in diabetes-prone mice has the potential to prevent transition to full-blown disease depending on the presence of IL-4.

Regulatory T cells and allergic asthma

Because of the characteristic airway inflammation observed in allergic asthma, the pathogenesis of this disease may be due, in part, to a lack of anti-inflammatory and immune suppressive mechanisms. Here, we discuss the possible involvement and therapeutic use of T regulatory cells and their soluble factors in this multifactorial disease.

Lipopolysaccharide-activated B cells down-regulate Th1 immunity and prevent autoimmune diabetes in nonobese diabetic mice

B cells can serve dual roles in modulating T cell immunity through their potent capacity to present Ag and induce regulatory tolerance. Although B cells are necessary components for the initiation of spontaneous T cell autoimmunity to beta cell Ags in nonobese diabetic (NOD) mice, the role of activated B cells in the autoimmune process is poorly understood. In this study, we show that LPS-activated B cells, but not control B cells, express Fas ligand and secrete TGF-beta. Coincubation of diabetogenic T cells with activated B cells in vitro leads to the apoptosis of both T and B lymphocytes. Transfusion of activated B cells, but not control B cells, into prediabetic NOD mice inhibited spontaneous Th1 autoimmunity, but did not promote Th2 responses to beta cell autoantigens. Furthermore, this treatment induced mononuclear cell apoptosis predominantly in the spleen and temporarily impaired the activity of APCs. Cotransfer of activated B cells with diabetogenic splenic T cells prevented the adoptive transfer of type I diabetes mellitus (T1DM) to NOD/scid mice. Importantly, whereas 90% of NOD mice treated with control B cells developed T1DM within 27 wk, <20% of the NOD mice treated with activated B cells became hyperglycemic up to 1 year of age. Our data suggest that activated B cells can down-regulate pathogenic Th1 immunity through triggering the apoptosis of Th1 cells and/or inhibition of APC activity by the secretion of TGF-beta. These findings provide new insights into T-B cell interactions and may aid in the design of new therapies for human T1DM.

Experimental autoimmune myocarditis in A/J mice is an interleukin-4-dependent disease with a Th2 phenotype

Myocarditis in humans is often associated with an autoimmune process in which cardiac myosin (CM) is a major autoantigen. Experimental autoimmune myocarditis (EAM) is induced in mice by immunization with CM. We found that EAM in A/J mice exhibits a Th2-like phenotype demonstrated by the histological picture of the heart lesions (eosinophils and giant cells) and by the humoral response (association of IgG1 response with disease and up-regulation of total IgE). Blocking interleukin (IL)-4 with anti-IL-4 monoclonal antibody (mAb) reduced the severity of EAM. This reduction in severity was associated with a shift from a Th2-like to a Th1-like phenotype represented by a reduction in CM-specific IgG1; an increase in CM-specific IgG2a; an abrogation of total IgE response; a decrease in IL-4, IL-5, and IL-13; as well as a dramatic increase in interferon (IFN)-gamma production in vitro. Based on the latter finding, we hypothesized that IFN-gamma limits disease. Indeed, IFN-gamma blockade with a mAb exacerbated disease. The ameliorating effect of IL-4 blockade was abrogated by co-administration of anti-IFN-gamma mAb. Thus, EAM represents a model of an organ-specific autoimmune disease associated with a Th2 phenotype, in which IL-4 promotes the disease and IFN-gamma limits it. Suppression of IFN-gamma represents at least one of the mechanisms by which IL-4 promotes EAM.

The regulatory role of DR4 in a spontaneous diabetes DQ8 transgenic model

MHC class II molecules are critical determinants of genetic susceptibility to human type 1 diabetes. In patients, the most common haplotype contains the DRA1*0101-DRB1*0401 (DR4) and DQA1*0301-DQB1*0302 (DQ8) loci. To assess directly the relative roles of HLA-DQ8 and DR4 for diabetes development in vivo, we generated C57BL/6 transgenic mice that lack endogenous mouse MHC class II molecules but express HLA-DQ8 and/or DR4. Neither HLA-DQ nor HLA-DR transgenic mice developed insulitis or spontaneous diabetes. However, when they were crossed to transgenic mice (C57BL/6) expressing the B7.1 costimulatory molecules on pancreatic beta cells that do not normally develop diabetes, T cells from these double transgenic mice were no longer tolerant to islet autoantigens. The majority of DQ8/RIP-B7 mice developed spontaneous diabetes, whereas only 25% of DR4/RIP-B7 mice did so. Interestingly, when DQ8 and DR4 were coexpressed (DQ8DR4/RIP-B7), only 23% of these mice developed diabetes, an incidence indistinguishable from the DR4/RIP-B7 mice. T cells from both DR4/RIP-B7 and DQ8DR4/RIP-B7 mice, unlike those from DQ8/RIP-B7 mice, exhibited a Th2-like phenotype. Thus, the expression of DR4 appeared to downregulate DQ8-restricted autoreactive T cells in DQ8DR4/RIP-B7 mice. Our data suggest that although both DQ8 and DR4 can promote spontaneous diabetes in mice with a non-autoimmune-prone genetic background, the diabetogenic effect of the DQ8 allele is much greater, whereas DR4 expression downregulates the diabetogenic effect of DQ8, perhaps by enhancing Th2-like immune responses.

Redirection of T cell effector function in vivo and enhanced collagen-induced arthritis mediated by an IL-2R beta/IL-4R alpha chimeric cytokine receptor transgene

Chronic inflammatory autoimmune diseases such as diabetes, experimental autoimmune encephalomyelitis, and collagen-induced arthritis (CIA) are associated with type 1 (Th1, Tc1) T cell-dependent responses against autoantigens. Immune deviation toward type 2 (Th2, Tc2) response has been proposed as a potential means of gene therapy or immunomodulation to treat autoimmune diseases based on evidence that type 2 cytokines can prevent or alleviate these conditions. In this report we assessed the effects of elevated type 2 responses on CIA using transgenic mice expressing an IL-2R beta/IL-4R alpha chimeric cytokine receptor transgene specifically in T cells. In response to IL-2 binding, this chimeric receptor transduces IL-4-specific signals and dramatically enhances type 2 responses. In contrast to published reports of Th2-mediated protection, CIA was exacerbated in IL-2R beta/IL-4R alpha chimeric receptor transgenic mice, with increased disease incidence, severity, and earlier disease onset. The aggravated disease in transgenic mice was associated with an increase in type 2 cytokines (IL-4, IL-5, IL-10) and an increase in collagen-specific IgG1 levels. However, IFN-gamma production is not affected significantly in the induction phase of the disease. There is also an extensive eosinophilic infiltration in the arthritic joints of the transgenic animal, suggesting a direct contribution of type 2 response to joint inflammation. Taken together, our findings provide novel evidence that enhancement of a polyclonal type 2 response in immunocompetent hosts may exacerbate an autoimmune disease such as CIA, rather than serving a protective role. This finding raises significant caution with regard to the potential use of therapeutic approaches based on immune deviation toward type 2 responses.

Intestinal parasitism terminates self tolerance and enhances neonatal induction of autoimmune disease and memory

Genetic and environmental factors both influence autoimmune disease occurrence, but the identity and mechanism of action of environmental factors are poorly understood. Here we show that pinworm-infected neonatal but not adult mice, injected with an ovarian self peptide of the zona pellucida protein 3 (pZP3) in water and without adjuvant, develop Th2 responses and severe eosinophilic autoimmune ovarian disease. A strong Th2 memory response is recalled when, as adults, the mice are challenged with a regimen that elicits a strong Th1 response in naive adults. The strong Th2 autoimmune response included high levels of IL-4 and IL-5 production by pZP3-specific T cells, and an IgG1-biased autoantibody response. The Th2 response ended promptly upon pinworm eradication, and partially resurfaced upon re-infection. We conclude that the rodent pinworm is an environmental agent that modifies the neonatal response to a self peptide, resulting in termination of the tolerance state and induction of a strong Th2-associated autoimmune disease and T cell memory.

Comparison of a T cell clone and of T cells from a TCR transgenic mouse: TCR transgenic T cells specific for self-antigen are atypical

It has been widely assumed that T cells from TCR-transgenic (Tg) mice better represent the behavior of T cells from normal mice than do in vitro cultures of T cell clones. We have found that autoreactive T cells arising in the presumably more physiological environment of the BDC-2.5 TCR-Tg mouse, despite being apparently "naive" in surface phenotype, are highly activated functionally and do not resemble CD4(+) T cells from a spontaneously diabetic nonobese diabetic (NOD) mouse or the NOD-derived, diabetogenic CD4(+) T cell clone of origin, BDC-2.5. Our results suggest that autoreactive T cells cloned from the spontaneously diabetic NOD mouse more closely resemble effector T cells arising during the natural disease process.

IL-4 triggers autoimmune diabetes by increasing self-antigen presentation within the pancreatic Islets

Several findings have recently questioned the long held hypothesis that cytokines belonging to the Th2 pathway are protective in T-cell-mediated autoimmunity. Among them, there is our previous report that pancreatic expression of IL-4 activated islet antigen-specific BDC2.5 T cells and rendered them able to trigger insulin-dependent diabetes mellitus in ins-IL-4/BDC2.5 mice (Mueller et al., Immunity, 7, 1997). Here we analyze the mechanisms underlying IL-4-mediated activation of the self-reactive BDC2.5 T cells. IL-4 is mainly known as the Th2-driving cytokine. However, IL-4 is also critical for DC maturation and upregulation of antigen uptake and presentation by macrophages. In our model, we found that pancreatic expression of IL-4 activated self-reactive BDC2.5 T cells by increasing islet antigen presentation by macrophages and dendritic cells. IL-4 could have triggered self-antigen presentation within the pancreatic islets both by driving maturation of DC from a tolerizing to a priming state and by increasing self-antigen uptake by macrophages.

Th1 to Th2 cytokine shifts in nonobese diabetic mice: sometimes an outcome, rather than the cause, of diabetes resistance elicited by immunostimulation

Numerous immunostimulatory protocols inhibit the development of T cell-mediated autoimmune insulin-dependent diabetes mellitus (IDDM) in the nonobese diabetic (NOD) mouse model. Many of these protocols, including treatment with the nonspecific immunostimulatory agents CFA or bacillus Calmette-Guérin (BCG) vaccine, have been reported to mediate protection by skewing the pattern of cytokines produced by pancreatic beta-cell autoreactive T cells from a Th1 (IFN-gamma) to a Th2 (IL-4 and IL-10) profile. However, most of these studies have documented associations between such cytokine shifts and disease protection rather than a cause/effect relationship. To partially address this issue we produced NOD mice genetically deficient in IFN-gamma, IL-4, or IL-10. Elimination of any of these cytokines did not significantly alter the rate of spontaneous IDDM development. Additional experiments using these mice confirmed that CFA- or BCG-elicited diabetes protection is associated with a decreased IFN-gamma to IL-4 mRNA ratio within T cell-infiltrated pancreatic islets, but this is a secondary consequence rather than the cause of disease resistance. Unexpectedly, we also found that the ability of BCG and, to a lesser extent, CFA to inhibit IDDM development in standard NOD mice is actually dependent upon the presence of the Th1 cytokine, IFN-gamma. Collectively, our studies demonstrate that while Th1 and Th2 cytokine shifts may occur among beta-cell autoreactive T cells of NOD mice protected from overt IDDM by various immunomodulatory therapies, it cannot automatically be assumed that this is the cause of their disease resistance.

Variable effects of transgenic c-Maf on autoimmune diabetes

Autoimmune diabetes is associated with T helper 1 polarization, but protection from disease can be provided by the application of T helper 2 (Th2) cytokines. To test whether genetic manipulation of T-cells can provide protective Th2 responses, we developed transgenic mice in which T-cells express the interleukin-4-specific transcription factor c-Maf. When crossed with a transgenic model that combines a class II restricted T-cell receptor specific for influenza hemagglutinin with islet beta-cell expression of hemagglutinin, the c-Maf transgene provided significant protection from spontaneous autoimmunity but not from adoptively transferred diabetes. In a second transgenic model in which islet cells express the lymphocytic choriomeningitis virus nucleoprotein, the virus infection triggers autoimmune diabetes within a few weeks involving both CD4 and CD8 T-cells; here too transgenic c-Maf provided significant protection. Surprisingly, when the c-Maf transgene was backcrossed with the NOD model of spontaneous disease, no protection was evident. Thus, transgenic c-Maf can strongly influence autoimmune disease development in some models, but additional factors, such as background genetic differences, can influence the potency of its effect.

Islet allograft rejection can be mediated by CD4+, alloantigen experienced, direct pathway T cells of TH1 and TH2 cytokine phenotype

BACKGROUND

It is widely believed that Thl cells that secrete interferon-gamma are primarily involved in the rejection of allografts whereas Th2 cells [interleukin(IL) 4 and IL-10] are thought to be protective of this process. However, the exact role and specificity of these helper T lymphocytes in mediating allograft damage is presently unknown.

METHODS

Th0, Th1, and Th2 cell lines specific for the class II MHC molecule H2IAb were adoptively transferred into T cell deficient, syngeneic, diabetic mice before transplantation of fully allogeneic C57BL/10 (H2b) or (CBKxBALB/c)F1 (H2k/d+Kb) islet grafts. T cells were 5-(and-6-)-carboxyfluorescein diacetate succinimidyl ester- (CFSE) labeled to allow detection, immunohistochemistry was performed, and IL-4 transcripts within the rejected islet grafts were quantified by reverse transcriptase polymerase chain reaction (RT-PCR).

RESULTS

Adoptive transfer (IV) of Th0-, Th1-, and Th2 IAb-specific T cells resulted in rejection of H2b islet allografts. CFSE-labeling demonstrated that these T cells were able to home to the graft site. CD4+ T cells and CD11b+ macrophages were present within the graft after adoptive transfer of both Thl and Th2 cells. Interestingly, CD8+ T cells and B cells were absent from these rejecting grafts. Even when Th2 cells were introduced directly at the graft site, prompt rejection was still observed despite the presence of increased IL-4 mRNA expression within the islet allografts.

CONCLUSIONS

Th2 and Th0 alloreactive CD4+ T helper cells can reject islet grafts with similar efficiency to Th1 cells. These results suggest that deviation of the immune response from a Th1 to Th2 phenotype will not be sufficient to allow successful engraftment of allogeneic organs or tissues.

Relative diabetogenic properties of islet-specific Tc1 and Tc2 cells in immunocompetent hosts

CD8(+) T cells are important effectors, as well as regulators, of organ-specific autoimmunity. Compared with Tc1-type CD8(+) cells, Tc2 cells have impaired anti-viral and anti-tumor effector functions, although no data are yet available on their pathogenic role in autoimmunity. Our aim was to explore the role of autoreactive Tc1 and Tc2 cells in autoimmune diabetes. We set up an adoptive transfer model in which the recipients were transgenic mice expressing influenza virus hemagglutinin (HA) specifically in their pancreatic ss islet cells (rat insulin promoter-HA mice) and islet-specific Tc1 and Tc2 cells were generated in vitro from HA-specific CD8(+) cells of TCR transgenic mice (CL4-TCR mice). One million Tc1 cells, differentiated in vitro in the presence of IL-12, transferred diabetes in 100% of nonirradiated adult rat insulin promoter-HA recipients; the 50% diabetogenic dose was 5 x 10(5). Highly polarized Tc2 cells generated in the presence of IL-4, IL-10, and anti-IFN-gamma mAb had a relatively low, but definite, diabetogenic potential. Thus, 5 x 10(6) Tc2 cells caused diabetes in 6 of 18 recipients, while the same dose of naive CD8(+) cells did not cause diabetes. Looking for the cause of the different diabetogenic potential of Tc1 and Tc2 cells, we found that Tc2 cells are at least as cytotoxic as Tc1 cells but their accumulation in the pancreas is slower, a possible consequence of differential chemokine receptor expression. The diabetogenicity of autoreactive Tc2 cells, most likely caused by their cytotoxic activity, precludes their therapeutic use as regulators of autoimmunity.

A targeted mutation in the IL-4Ralpha gene protects mice against autoimmune diabetes

Autoimmune insulin-dependent diabetes mellitus (IDDM) occurs spontaneously in mice-bearing transgenes encoding the influenza hemagglutinin under the control of the rat insulin promoter and a T cell receptor specific for an hemagglutinin peptide associated with I-E(d). Such "double transgenic" mice expressing wild-type or targeted IL-4Ralpha genes were examined for the onset of IDDM. Eight of 11 mice homozygous for wild-type IL-4Ralpha were hyperglycemic by 8 weeks of age, whereas only 1 of 16 mice homozygous for the targeted allele were hyperglycemic at this time. Most 1L-4Ralpha-/- mice remained normoglycemic to 36 weeks of age. Although only 10% of double transgenic mice homozygous for the wild-type IL-4Ralpha allele survived to 30 weeks, 80% of mice homozygous for the targeted allele did so. Heterozygous mice displayed an intermediate frequency of diabetes. Even as late as 270 days of age, mice homozygous for the targeted allele had no insulitis or only peri-insulitis. Thus, the inability to respond to IL-4 and/or IL-13 protects mice against IDDM in this model of autoimmunity.

Limited CD4 T-cell diversity associated with colitis in T-cell receptor alpha mutant mice requires a T helper 2 environment

BACKGROUND & AIMS

T-cell receptor alpha mutant (TCRalpha(-/-)) mice spontaneously develop chronic colitis mediated by CD4(+) TCRalpha(-)beta(+) T cells. The aim of this study was to analyze the mechanisms of expansion of these cells by characterization of the TCRbeta repertoire.

METHODS

TCRbeta repertoire was analyzed by reverse-transcription polymerase chain reaction/Southern blot and DNA sequencing. Clonality of T cells was examined in the lymphoid tissues and colons of TCRalpha(-/-) mice and interleukin 4-deficient TCRalpha(-/-) mice. In addition, an in vitro culture system using syngeneic colonic epithelial cells as antigens was used.

RESULTS

The clonal expansion of a restricted subset of Vbeta8.2(+) T cells was characterized by conservation of a single negatively charged amino acid residue in the second position of the complementarity-determining region 3 (CDR3). These T cells were observed in the diseased colon and appendix (cecal patch) of TCRalpha(-/-) mice, but not germfree TCRalpha(-/-) mice. Culture of polyclonal T cells from young TCRalpha(-/-) mice with colonic epithelial cells under T helper 2 conditions resulted in the survival of Vbeta8.2(+) T cells characterized by the same CDR3 pattern. In addition, the transfer of the cultivated T cells induced mild colitis in recombination-activating gene 1 mutant mice.

CONCLUSIONS

In the TCRalpha(-/-) mice, the development of colitis is associated with the presence of a restricted diversity of Vbeta8. 2(+) T-cell subsets characterized by a specific TCR motif. The limited diversity of lamina propria T cells that are derived from naive T cells expanded by reacting with luminal bacterial antigens is likely caused by the survival of these T cells after stimulation with self-antigens in the presence of a T helper 2 environment.

IL-4 is a mediator of IL-12p70 induction by human Th2 cells: reversal of polarized Th2 phenotype by dendritic cells

IL-12 is a key inducer of Th1-associated inflammatory responses, protective against intracellular infections and cancer, but also involved in autoimmune tissue destruction. We report that human Th2 cells interacting with monocyte-derived dendritic cells (DC) effectively induce bioactive IL-12p70 and revert to Th0/Th1 phenotype. In contrast, the interaction with B cells preserves polarized Th2 phenotype. The induction of IL-12p70 in Th2 cell-DC cocultures is prevented by IL-4-neutralizing mAb, indicating that IL-4 acts as a Th2 cell-specific cofactor of IL-12p70 induction. Like IFN-gamma, IL-4 strongly enhances the production of bioactive IL-12p70 heterodimer in CD40 ligand-stimulated DC and macrophages and synergizes with IFN-gamma at low concentrations of both cytokines. However, in contrast to IFN-gamma, IL-4 inhibits the CD40 ligand-induced production of inactive IL-12p40 and the production of either form of IL-12 induced by LPS, which may explain the view of IL-4 as an IL-12 inhibitor. The presently described ability of IL-4 to act as a cofactor of Th cell-mediated IL-12p70 induction may allow Th2 cells to support cell-mediated immunity in chronic inflammatory states, including cancer, autoimmunity, and atopic dermatitis.

IL-10 deficiency does not inhibit insulitis and accelerates cyclophosphamide-induced diabetes in the nonobese diabetic mouse

IL-10 exterts profound immunostimulatory and immunoinhibitory effects. To explore the role of IL-10 in autoimmune diabetes of nonobese diabetic (NOD) mice, we generated IL-10-deficient NOD mice. In contrast to our previous results with neutralizing antibodies to IL-10, IL-10-deficient NOD mice developed insulitis and their splenocytes readily responded to islet antigen glutamic acid decarboxylase 65. IL-10-deficient NOD mice did not develop accelerated spontaneous diabetes. On the other hand, IL-10-deficient NOD mice developed accelerated disease following cyclophosphamide (CYP) injection. These findings demonstrate that IL-10 is dispensable for autoimmune diabetes. IL-10's absence fails to accelerate endogenous diabetes but potentiates CYP-induced diabetes.

Revisiting tolerance induced by autoantigen in incomplete Freund's adjuvant

Injection of autoantigens in IFA has been one of the most effective ways of preventing experimental, T cell-mediated, autoimmune disease in mice. The mechanism that underlies this protection has, however, remained controversial, with clonal deletion, induction of suppressor cells or of type 2 immunity being implicated at one time or another. Using high resolution enzyme-linked immunospot (ELISPOT) analysis, we have revisited this paradigm. As models of autoimmunity against sequestered and readily accessible autoantigens, we studied experimental allergic encephalomyelitis, induced by myelin oligodendrocyte glycoprotein, proteolipid protein, myelin basic protein, and renal tubular Ag-induced interstitial nephritis. We showed that the injection of each of these Ags in IFA was immunogenic and CD4 memory cells producing IL-2, IL-4, and IL-5, but essentially no IFN-gamma. IgG1, but not IgG2a, autoantibodies were produced. The engaged T cells were not classic Th2 cells in that IL-4 and IL-5 were produced by different cells. The IFA-induced violation of self tolerance, including the deposition of specific autoantibodies in the respective target organs, occurred in the absence of detectable pathology. Exhaustion of the pool of naive precursor cells was shown to be one mechanism of the IFA-induced tolerance. In addition, while the IFA-primed T cells acted as suppressor cells, in that they adoptively transferred disease protection, they did not interfere with the emergence of a type 1 T cell response in the adoptive host. Both active and passive tolerance mechanisms, therefore, contribute to autoantigen:IFA-induced protection from autoimmune disease.

Spontaneous chronic colitis in TCR alpha-mutant mice; an experimental model of human ulcerative colitis

Mice with targeted disruption of the T cell receptor alpha gene (TCR alpha-/-) spontaneously develop chronic colitis. Colonic inflammation begins at 6-8 weeks of age and chronic colitis is established in about 60% of mice by 16-20 weeks of age. The disease is also associated with autoantibodies (anti-tropomyosin antibodies, anti-neutrophil cytoplasmic antibodies) and an oligoclonal immune response to luminal bacterial antigens. Although T cells, but not B cells or autoantibodies, are essential for the development of colitis, B cells and/or autoantibodies may have a regulatory role in the pathogenesis of this colitis because the colitis is more severe in B cell deficient TCR alpha-/- mice. Cytokines, specifically IL-4 and IL-1, also play an important role in the development of colitis in TCR alpha-/- mice. Enteric bacteria located in the large intestine are an important factor in the pathogenesis of this colitis because germ-free TCR alpha-/- mice do not develop colitis and appendectomy at an early age delays the onset of this colitis. The colitis in TCR alpha-/- mice resembles human ulcerative colitis and provides a useful model to study the pathogenesis of human inflammatory bowel disease.

Th1 and Th2 mediate acute graft-versus-host disease, each with distinct end-organ targets

STAT4 and STAT6 are transcription factors that play crucial roles in responding to IL-12 and IL-4, respectively. STAT4 gene knockout (STAT4(-/-)) mice have markedly reduced Th1 responses and enhanced Th2 responses. STAT6(-/-) mice show the inverse phenotype. We compared the ability of bone marrow transplantation (BMT) with the inclusion of spleen cells from STAT6(-/-), STAT4(-/-), and wild-type (WT) mice to produce graft-versus-host disease (GVHD) in lethally irradiated MHC-mismatched recipients. Acute GVHD mortality was more rapid when induced by cells from STAT6(-/-) mice than when induced by STAT4(-/-) cells. However, cells from STAT4(-/-) and STAT6(-/-) donors both induced delayed GVHD mortality compared with WT controls, or compared with combined STAT4(-/-) and STAT6(-/-) cells, indicating a contribution of both Th1 cells and Th2 cells to acute GVHD. Recipients of STAT6(-/-) BMT showed evidence of acute GVHD with severe diarrhea and marked weight loss. Recipients of STAT4(-/-) BMT showed signs of GVHD with only initial transient weight loss and later development of severe skin GVHD. Histopathology showed that Th2 responses were required for the induction of both hepatic and severe skin GVHD. In contrast, both Th1 cells and Th2 cells were capable of causing intestinal pathology of GVHD. Our studies demonstrate an additive role for Th1 and Th2 cells in producing acute GVHD, and suggest a cytokine-directed approach to treating end-organ manifestations of GVHD.