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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.

Animals↗

Requirements for autoimmune responses to mouse gastric autoantigens.

Autoimmune gastritis, in which the H+/K(+)-ATPase of parietal cells is the major antigen, is one of the most common autoimmune diseases. Here we examined if specific properties of the H+/K(+)-ATPase or parietal cells are involved in rendering them autoimmune targets. The model antigens beta-galactosidase and ovalbumin (OVA) were expressed in parietal cells of transgenic mice. On experimental induction of autoimmune gastritis by neonatal thymectomy, autoantibodies to beta-galactosidase developed in mice expressing beta-galactosidase in parietal cells, a response that was independent of either the response to the gastric H+/K(+)-ATPase or gastric inflammation. In contrast, mice that expressed OVA in parietal cells did not exhibit an antibody response to OVA after thymectomy. However, increasing the frequency of anti-OVA T lymphocytes in OVA-expressing mice resulted in autoantibodies to OVA and gastritis. These studies indicate that parietal cells can present a variety of antigens to the immune system. Factors such as the identity and expression level of the autoantigen and the frequency of autoreactive T cells play a role in determining the prevalence and outcome of the particular immune response. In addition, as not all mice of a particular genotype displayed autoimmunity, random events are involved in determining the target of autoimmune recognition.

Animals↗

The genes of systemic autoimmunity.

Autoimmune diseases include a wide spectrum of disorders, which have been divided into systemic and organ-specific disorders. Lupus, the prototypic systemic autoimmune disease, is characterized by female predominance, multiorgan pathology, and autoantibodies, primarily directed against nuclear antigens. The disease is heterogeneous, with variable organ involvement, serology, and clinical course. Susceptibility to lupus is inherited as a polygenic trait with added contributions from environmental and stochastic variance. Concerted efforts have recently been made by several laboratories to define the genetic basis of this disease in predisposed mice and humans. The identification of the Fas/FasL defects in lpr and gld lupus mice was the first example of spontaneous mutations of apoptosis-promoting genes being associated with systemic autoimmunity. This research was instrumental in clarifying the roles of these genes in tolerance and immunoregulation, and in extrapolating these results to other autoimmune diseases, as well as cancer and transplantation. To these findings have been added those from transgenic and gene knockout mouse studies that have helped to define the systemic autoimmunity-inducing or -modifying effects of specific genes in normal background and lupus-congenic mice. In addition, the findings from genome-wide searches have begun to identify predisposing loci (and ultimately genes) for the spontaneous lupus-like diseases in various mouse strains and in humans. The emerging picture is that multiple genetic contributions can independently lead to systemic autoimmunity in mice, which reinforces the view that human lupus may be similarly composed of diverse genotypes. This complexity underscores the importance of defining the predisposing alleles and mechanisms of action, an undertaking that is certainly feasible given current technologies and future advances in the definition of mammalian genomes.

Animals↗

The etiopathogenesis of autoimmunity.

Acquisition by mammals of an adaptive immune system was an evolutionary leap, but occurred at the cost of autoimmunity. The necessity for self-recognition was appreciated in 1900, but autoimmune disease did not become a clinical reality until the 1950s-still the perimeters are indistinct. Autoimmune responses recapitulate the complex events of normal immune responses but cannot shut down. Immune tolerance is established during repertoire development centrally in thymus or bone marrow by deletion of self-reactive immunocytes, and is supplemented peripherally by regulatory T cells (Tregs). A startling discovery is the autoimmune regulator AIRE gene that enables expression of organ-specific autoantigens for intrathymic deletional tolerance of T cells. The origins, activities, and markers of Tregs are under intensive investigation. Of genes implicated in autoimmune, only few are characterized; contributions of environment are similarly uncertain. Time-latency considerations implicate stochastic factors or chance in the etiopathogenesis of autoimmunity, whether they are somatic mutations or successive random gene-environment interactions. Solutions to etiopathogenesis require novel experimental models and finely designed gene-environment studies on human populations. Perhaps immunomodulatory therapies will effect cures before causes are fully understood.

Animals↗

Transforming growth factor beta (TGF-beta)-dependent inhibition of T helper cell 2 (Th2)-induced autoimmunity by self-major histocompatibility complex (MHC) class II-specific, regulatory CD4(+) T cell lines.

Autoreactive anti-MHC class II T cells are found in Brown Norway (BN) and Lewis (LEW) rats that receive either HgCl2 or gold salts. These T cells have a T helper cell 2 (Th2) phenotype in the former strain and are responsible for Th2-mediated autoimmunity. In contrast, T cells that expand in LEW rats produce IL-2 and prevent experimental autoimmune encephalomyelitis, a cell-mediated autoimmune disease. The aim of this work was to investigate, using T cell lines derived from HgCl2-injected LEW rats (LEWHg), the effect of these autoreactive T cells on the development of Th2-mediated autoimmunity. The five LEWHg T cell lines obtained protect against Th2-mediated autoimmunity induced by HgCl2 in (LEW x BN)F1 hybrids. The lines produce, in addition to IL-2, IFN-gamma and TGF-beta, and the protective effect is TGF-beta dependent since protection is abrogated by anti-TGF-beta treatment. These results identify regulatory, TGF-beta-producing, autoreactive T cells that are distinct from classical Th1 or Th2 and inhibit both Th1- and Th2-mediated autoimmune diseases.

Adoptive Transfer↗

Gene dosage--limiting role of Aire in thymic expression, clonal deletion, and organ-specific autoimmunity.

Inactivation of the autoimmune regulator (Aire) gene causes a rare recessive disorder, autoimmune polyendocrine syndrome 1 (APS1), but it is not known if Aire-dependent tolerance mechanisms are susceptible to the quantitative genetic changes thought to underlie more common autoimmune diseases. In mice with a targeted mutation, complete loss of Aire abolished expression of an insulin promoter transgene in thymic epithelium, but had no effect in pancreatic islets or the testes. Loss of one copy of Aire diminished thymic expression of the endogenous insulin gene and the transgene, resulting in a 300% increase in islet-reactive CD4 T cells escaping thymic deletion in T cell receptor transgenic mice, and dramatically increased progression to diabetes. Thymic deletion induced by antigen under control of the thyroglobulin promoter was abolished in Aire homozygotes and less efficient in heterozygotes, providing an explanation for thyroid autoimmunity in APS1. In contrast, Aire deficiency had no effect on thymic deletion to antigen controlled by a systemic H-2K promoter. The sensitivity of Aire-dependent thymic deletion to small reductions in function makes this pathway a prime candidate for more subtle autoimmune quantitative trait loci, and suggests that methods to increase Aire activity would be a potent strategy to lower the incidence of organ-specific autoimmunity.

Animals↗

Iodine and thyroid autoimmune disease in animal models.

Thyroid autoimmune diseases are complex, polygenic afflictions the penetrance of which is heavily dependent on various environmental influences. In their pathogenesis, an afferent stage (enhanced autoantigen presentation), a central stage (excessive expansion and maturation of autoreactive T and B cells), and an efferent stage (effects of autoreactive T cells and B cells on their targets) can be discerned. At each stage, a plethora of inborn, endogenous or exogenous factors is able to elicit the abnormalities characteristic of that stage, thus opening the gateway to thyroid autoimmunity. Iodine is an important exogenous modulating factor of the process. In general, iodine deficiency attenuates, while iodine excess accelerates autoimmune thyroiditis in autoimmune prone individuals. In nonautoimmune prone individuals, the effects of iodine are different. Here iodine deficiency precipitates a mild (physiological) form of thyroid autoimmune reactivity. Iodine excess stimulates thymus development. Iodine probably exerts these effects via interference in the various stages of the autoimmune process. In the afferent and efferent stage, iodine-induced alterations in thyrocyte metabolism and even necrosis most likely play a role. By contrast, in the central phase, iodine has direct effects on thymus development, the development and function of various immune cells (T cells, B cells macrophages and dendritic cells) and the antigenicity of thyroglobulin.

Animals↗

Autoimmunity is a type I interferon-deficiency syndrome corrected by ingested type I IFN via the GALT system.

Type I interferons (IFN-alpha/beta), products of the innate immune system, can modulate immune function whereas proinflammatory IFN-gamma (type II IFN), a product of the acquired immune system upregulates inflammation and enhances cell mediated immunity. We have proposed a unifying hypothesis of the origin of autoimmunity as a type I IFN immunodeficiency syndrome involving inadequate regulation of the acquired immune system product IFN-gamma by the IFN-alpha/beta innate immune system. The common theme of ingested type I IFNs in autoimmunity is inhibition of proinflammatory type II IFN systemically or at the target organ. In multiple sclerosis (MS) and insulin-dependent diabetes mellitus (IDDM) at the target organ, and in rheumatoid arthritis (RA) as a regulator of other proinflammatory cytokines, IFN-gamma is the nexus of inflammation in autoimmunity. Ingested type I IFNs counteract type II IFN, overcome the relative lack of type I IFN activity, and ameliorate autoimmunity. The administration of type I IFNs (IFN-alpha/beta) via the gut offers an exciting alternative to systemic application for overcoming the type I IFN immunodeficiency in autoimmunity. Successful use of ingested type I IFN in three separate prototypical autoimmune diseases suggests a broad antiinflammatory therapeutic profile for this technology.

Administration, Oral↗

Genetic insights into disease mechanisms of autoimmunity.

Educating the immune system to distinguish between self and non-self is critical to ensure that an immune response is mounted against foreign antigens and not against self. A breakdown in these mechanisms can lead to the onset of autoimmune disease. Clinical and molecular data suggest that shared immunogenetic mechanisms lead to the autoimmune process. The most studied genes and molecules are the human leukocyte antigen (HLA) region and the cytotoxic T-lymphocyte-associated 4 molecule (CTLA-4). Recently progress has been achieved in narrowing down the primary variants within both gene regions, but further work is needed to determine the function and extent of the aetiological variant(s) present. Recent exciting results also suggest a role for the newly discovered lymphoid-specific phosphatase (LYP) protein. As well as these general mechanisms, disease-specific mechanisms are beginning to be elucidated, for example the role of autoimmune regulatory element 1 (AIRE1) in autoimmune polyendocrinopathy-candidiasis ectodermal dystrophy (APECED). Taken together, these data suggest that both general and disease-specific mechanisms lead to the clinical outcome of autoimmune disease and that increased understanding of these mechanisms will improve our knowledge of how autoimmune disease occurs, eventually leading to the development of novel therapeutic agents.

Antigens, CD↗

Mapping of an autoimmunity susceptibility locus (AIS1) to chromosome 1p31.3-p32.2.

Generalized vitiligo is a common autoimmune disorder in which patchy loss of skin and hair pigmentation results from loss of pigment-forming melanocytes from the involved regions. Vitiligo occurs with a frequency of about 1% in most populations, and is highly associated with other autoimmune disorders, particularly Hashimoto thyroiditis. Most cases of vitiligo are sporadic, although some cases cluster in families, and the disorder is thought to be oligogenic in origin. We have studied a large family cluster in which vitiligo and Hashimoto thyroiditis occur in numerous individuals. A whole-genome scan of 24 family members, including 14 affected with autoimmune disease, showed significant linkage of an oligogenic autoimmune susceptibility locus, termed AIS1, to a 14.4 cM interval in 1p31.3-p32.2. A two-locus analysis of Hashimoto thyroiditis in family members segregating an AIS1 susceptibility allele showed suggestive linkage to markers in chromosome 6p22.3-q14.1, in a region spanning both the major histocompatibility complex and AITD1, a susceptibility locus for autoimmune thyroid disease. Our results indicate that the 1p AIS1 locus is associated with susceptibility to autoimmunity, particularly vitiligo, in this family, and that a chromosome 6 locus, most likely AITD1, may mediate the occurrence of Hashimoto's thyroiditis in AIS1-susceptible family members.

Autoimmunity↗

Murine models of autoimmune disease and Sjögren's syndrome.

Murine models of autoimmune disease exhibit heterogenous features that are now being understood in terms of their basic molecular defects. Defects in apoptosis genes or genes that contribute to B-cell activation, T-cell tolerance loss, and development of autoimmune disease, including glomerulonephritis, have been identified. The interaction of primary and secondary predisposing genes leads to a diverse spectrum of autoimmune features that is different in different strains of mice. The challenge in the future will be to correlate these primary and secondary autoimmune genes with specific environmental triggers to explain the diverse spectrum of autoimmune disease. The ability to correct the apoptosis defect and autoimmune disease in CD2-Fas transgenic MRL-lpr/lpr mice brings hope that genetic therapy will eventually be possible in humans.

Animals↗

Autoimmunity and hypothyroidism in patients with uveal melanoma.

Among patients with advanced melanoma, the development of autoimmune phenomena or of hypothyroidism during therapy has been associated with a favourable outcome. The objective of this study was to determine the prevalence of autoimmunity and of hypothyroidism in the melanoma population as a whole and to determine if these disease states confer a survival advantage for patients with metastatic disease. We report our findings in the uveal melanoma population. The study population (n = 91) consisted of all patients registered at this institution with the diagnosis of uveal melanoma during a 2 year study period. Eight (8.8%) had a systemic autoimmune disease; 12 (13.2%) were hypothyroid, including 9/46 (19.6%) females. Survival of the stage 4 patients was determined from diagnosis of the primary tumour (SvDx) and from diagnosis of metastatic disease (SvMt), and was compared to that of age/sex matched stage 4 controls. For autoimmune patients versus controls, the median SvDx was 111 months vs 37 months (P = 0.2734) and the median SvMt was 17 months vs 4 months (P = 0.0887). For the hypothyroid patients versus controls, the median SvDx was 58 months vs 49 months (P = 0.5348) and the median SvMt was 4 months vs 8 months (P = 0.2437). We conclude that there is a trend toward longer survival from the date of metastasis in uveal melanoma patients with a systemic autoimmune disorder, suggesting that systemic autoimmunity may play a role in modifying the activity of established metastases. This trend is not seen among the uveal melanoma patients with hypothyroidism. The high prevalence of hypothyroidism suggests a possible molecular interaction between the two disease processes.

Adult↗

Post-streptococcal autoimmune disorders of the central nervous system.

PURPOSE OF REVIEW: Autoimmune disease has long been intertwined with investigations of infectious causes. Antibodies that are formed against an infectious agent can, through the process of molecular mimicry, also recognize healthy cells. When this occurs, the immune system erroneously destroys the healthy cells causing autoimmune disease in addition to appropriately destroying the offending infectious agent and attenuating the infectious process. The first infectious agent shown to cause a post-infectious autoimmune disorder in the central nervous system was Streptococcus pyogenes in Sydenham's chorea. The present review summarizes the most recent published findings of central nervous system diseases that have evidence of a post-streptococcal autoimmune etiology. RECENT FINDINGS: Sydenham's chorea and other central nervous system illnesses that are hypothesized to have a post-streptococcal autoimmune etiology appear to arise from targeted dysfunction of the basal ganglia. PANDAS (pediatric autoimmune disorders associated with streptococcal infections) is the acronym applied to a subgroup of children with obsessive-compulsive disorder or tic disorders occurring in association with streptococcal infections. In addition, there are recent reports of dystonia, chorea encephalopathy, and dystonic choreoathetosis occurring as sequelae of streptococcal infection. Investigators have begun to isolate and describe antistreptococcal-antineuronal antibodies as well as possible genetic markers in patients who are susceptible to these illnesses. SUMMARY: Clinical and research findings in both immunology and neuropsychiatry have established the existence of post-streptococcal neuropsychiatric disorders and are beginning to shed light on possible pathobiologic processes.

Animals↗

Successful treatment of de novo autoimmune hepatitis and cirrhosis after pediatric liver transplantation.

Over a 15-yr period of observation, among the 205 children who underwent liver transplantations, one of them developed a particular type of late graft dysfunction with clinical and histological similarity to autoimmune hepatitis. The patient had alpha1-antitrypsin deficiency and did not previously have autoimmune hepatitis or any other autoimmune disease before transplantation. Infectious and surgical complications were excluded. After repeated episodes of unexplained fluctuations of liver function tests and liver biopsies demonstrating reactive or a biliary pattern, without any corresponding alteration of percutaneous cholangiography, a liver-biopsy sample taken 4 yr after the transplant showed active chronic hepatitis progressing to cirrhosis, portal lymphocyte aggregates, and a large number of plasma cells. At that time, autoantibodies (gastric parietal cell antibody, liver-kidney microsomal antibody, and anti-hepatic cytosol) were positive and serum IgG levels were high. Based on these findings of autoimmune disease, a diagnosis of 'de novo autoimmune hepatitis' was made. The treatment consisted of reducing the dose of cyclosporine, reintroduction of corticosteroids, and addition of mycophenolate mofetil. After 19 months of treatment, a new liver-biopsy sample showed marked reduction of portal and lobular inflammatory infiltrate, with regression of fibrosis and of the architectural disruption. At that time, serum autoantibodies became negative. The last liver-biopsy sample showed inactive cirrhosis and disappearance of interface hepatitis and of plasma cell infiltrate. Presently, 9 yr after the transplantation, the patient is doing well, with normal liver function tests and no evidence of cirrhosis. Her immunosuppressive therapy consists of tacrolimus, mycophenolate mofetil, and prednisolone. In conclusion, the present case demonstrates that de novo autoimmune hepatitis can appear in liver-transplant patients despite appropriate anti-rejection immunosuppression, and triple therapy with tacrolimus, mycophenolate mofetil, and prednisolone could sustain the graft and prevent retransplantation.

Autoimmune Diseases↗

Recent developments in autoimmune liver diseases.

Several diseases are regarded as autoimmune liver diseases. Apart from the cholestatic liver diseases, primary biliary cirrhosis, primary sclerosing cholangitis, these include autoimmune hepatitis, hepatitis as part of the autoimmune polyendocrine syndrome type 1 (APS-1) and particular overlap syndromes such as autoimmune cholangitis (also called antimitochondrial antibody negative primary biliary cirrhosis [PBC]), overlap syndrome chronic active hepatitis (CAH)/PBC and the overlap syndrome primary sclerosing hepatitis (PSC)/CAH. In addition, auto-antibodies may be observed during the course of chronic viral hepatitis, in particular chronic hepatitis C and D. Finally, a small number of drug-induced liver diseases is immune mediated. The following article will review our recent progress in the field of autoimmune hepatitis including APS-1 and autoimmunity in viral hepatitis and immune-mediated drug-induced liver disease.

Antibody Formation↗

LKM-positive autoimmune hepatitis in the western United States: a case series.

OBJECTIVE: LKM-positive, or type 2, autoimmune hepatitis is characterized by the presence of antibodies directed against liver-kidney microsomes (LKM1). Although described frequently in southern Europe and the Mediterranean, this subtype of autoimmune liver disease seems to be extremely rare in northern Europe and in the United States. We report here five cases of LKM-positive autoimmune hepatitis that were seen at our center in the period 1989-1999. METHODS: We reviewed the medical records of all patients with the diagnosis of AIH in our institution during the period 1989-1999, and found that five patients had type 2 AIH. All patients were female; four of five were young, and four of five presented with overt cirrhosis. RESULTS: One patient died, one underwent liver transplantation and two are currently awaiting liver transplantation. Response to conventional immunosuppressive therapy was poor and two patients required treatment with cyclosporine and tacrolimus respectively. Four of five patients had at least one associated autoimmune disorder, including IgE-induced IgA deficiency, idiopathic thrombocytopenic purpura (ITP), and arthritis. HLA class II DR4 was present in two patients. CONCLUSIONS: LKM-positive autoimmune hepatitis seems to be a subset of autoimmune hepatitis with distinct clinical features; although rare, it is occasionally encountered in the western United States. Prompt diagnosis and appropriate immunosuppressive treatment are recommended, as well as early referral to transplantation centers. Clinicians should be aware of this condition in the setting of young female patients with unexplained severe liver disease.

Adult↗

Post-thymectomy murine experimental autoimmune oophoritis is associated with reduced natural killer cell activity.

PROBLEM: Natural killer (NK) cells can influence the immune response by secreting potent lymphokines. It has been suggested that NK cells have a suppressive action on B cells, and that impaired NK cell activity may play a role in some types of autoimmunity. NK cell abnormalities have been reported in women with premature ovarian failure. We therefore examined NK cell activity during the development of murine experimental autoimmune oophoritis, which serves as a model for autoimmune ovarian failure in women. METHOD OF STUDY: Neonatally thymectomized and sham-operated C57B1/6 x A/J (B6A) mice were prepared and sacrificed at 4, 6, 8, and 10 weeks after surgery. Splenic NK cell activity was determined in groups of five or more mice by measuring the percent specific lysis of target YAC-1 lymphoma cells using a standard 4-hr chromium release cytotoxicity assay. The number of splenic NK cells in neonatally thymectomized and sham-operated animals was also compared using flow cytometry. In a subsequent experiment, interleukin 12 (IL-12; NK cell-stimulating factor) was administered to neonatal mice before neonatal thymectomy. RESULTS: Neonatally thymectomized mice with associated autoimmune oophoritis had a 75% reduction in the number of splenic NK cells, and 50% or greater reduction in splenic NK cell activity at 4, 6, and 8 weeks after surgery. IL-12 treatment before neonatal thymectomy maintained NK cell activity and was shown to ameliorate the associated autoimmune oophoritis. CONCLUSION: Murine post-thymectomy autoimmune oophoritis is associated with reduced NK cell number and impaired NK cell activity, and in these respects the model is similar to premature ovarian failure in women. Research to define the relationship between NK cell abnormalities and the mechanism of ovarian failure in this model might lend insight into the pathogenesis of premature ovarian failure in women.

Animals↗

T-cell receptor genes in autoimmunity.

T cells are primary participants in the pathogenesis of the MHC-dependent autoimmune diseases, and therefore, evidence for association of TCR V-gene repertoires with such disorders has been actively sought. With very few exceptions, no clear-cut evidence for correlation of particular RFLP-defined V-C-region genomic polymorphisms with autoimmune disease predisposition has thus far been demonstrated. With regard to TCR V-gene repertoires engaged in responses to autoantigens, restricted use of certain V beta and V alpha genes in response to myelin basic protein has been documented in animal models. In many spontaneous and experimentally induced animal and human autoimmune diseases, however, the picture is far from clear. Although dominance of certain TCR V genes has been noted, the clonal restrictions are not absolute; they differ from one study to another and from one patient to another. Such variations may be caused by MHC allele-dependent determinant selection mechanisms, secondary T-cell infiltrates in inflammatory sites, different patient populations and stages of disease, or the involvement of different pathogens that, nevertheless, lead to the same clinical entity. Overall, the results indicate that efforts to intervene therapeutically in autoimmune diseases by vaccination with modified T-cell clones, V region-synthetic peptides, or TCR blocking analogues may not be easily applicable. Further studies on the characterization of the specific antigens involved in autoimmune disease pathogenesis is required in order to accurately address the issue of TCR utilization in autoimmune diseases.

Animals↗