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The rat model is a widely used animal model in research, its popularity perhaps only surpassed by the mouse model. Rats are the preferred models for the study of transplantation and certain tumor and autoimmune diseases. In particular, the understanding of cardiovascular-related diseases and chronic inflammation has depended widely on the rat, from which models for both multiple sclerosis and rheumatoid arthritis have been derived. Until now, research in the rat has been hampered by a lack of precise gene-targeting technology in this model. This limitation, however, is rapidly changing; a recent example is the availability of B-cell-deficient rat strains obtained by the newly established zinc finger nucleases-targeting technology. As described in this issue of the European Journal of Immunology, genetic targeting of the rat, for example, using zinc finger nucleases-targeting technology, is likely to rapidly drive progress in the understanding of not only B-cell biology but also in the general understanding of rat disease models.

The bottleneck for the induction of collagen-induced arthritis in mice is the recognition of immunodominant type II collagen (CII) peptide (CII259-273) bound to the MHC class II molecule A(q). We have shown previously that the posttranslationally glycosylated lysine at position 264 in this epitope is of great importance for T cell recognition and tolerance induction to CII as well as for arthritis development. The Ncf1 gene, controlling oxidative burst, has been shown to play an important role for immune tolerance to CII. To investigate the effect of oxidation on the efficiency of immune-specific vaccination with MHC class II/glycosylated-CII peptide complexes, we used Ncf1 mutated mice. We demonstrate that normal reactive oxygen species (ROS) levels contribute to the establishment of tolerance and arthritis protection, because only mice with a functional oxidative burst were completely protected from arthritis after administration of the glycosylated CII259-273 peptide in complex with MHC class II. Transfer of T cells from vaccinated mice with functional Ncf1 protein resulted in strong suppression of clinical signs of arthritis in B10.Q mice, whereas the Ncf1 mutated mice as recipients had a weaker suppressive effect, suggesting that ROS modified the secondary rather than the primary immune response. A milder but still significant effect was also observed in ROS deficient mice. During the primary vaccination response, regulatory T cells, upregulation of negative costimulatory molecules, and increased production of anti-inflammatory versus proinflammatory cytokines in both Ncf1 mutated and wild type B10.Q mice was observed, which could explain the vaccination effect independent of ROS.

Objectives: The novel small molecule 9-chloro-2,3-dimethyl-6-(N,N-dimethylaminoethylamino-2-oxoethyl)-6H-indolo[2,3-b] quinoxaline (Rabeximod) reduces severity of arthritis in rodent models of rheumatoid arthritis (RA) and multiple sclerosis (MS). This study aimed to investigate the cellular target in vivo., Methods: Collagen antibody-induced arthritis (CAIA) is induced by monoclonal collagen type II antibodies and enhanced by lipopolysaccharide. It was investigated how and when Rabeximod operates on inflammatory cells after stimulation of either Toll-like receptor (TLR)4 (lipopolysaccharide) or TLR2 (lipomannan) in mice lacking functional signalling through TLR4 due to a spontaneous deletion of the Tlr4 gene., Results: Rabeximod efficiently prevented arthritis during the time window when TLR2 or TLR4 ligands activate inflammatory macrophages. The effect operated downstream of TLR activation as Rabeximod was highly therapeutic in CAIA enhanced through TLR2 stimuli in TLR4 deficient mice. In addition, it was found that the arthritis ameliorating effect of Rabeximod was time dependent, since inhibition of tumour necrosis factor alpha production from macrophages in vitro was more pronounced if administered close to stimulation., Conclusions: Rabeximod suppresses arthritis by preventing activation of inflammatory cells, most likely macrophages, in a time dependent fashion, downstream of TLR2 and TLR4 stimulation.

The discovery of antibodies specific for citrullinated protein epitopes [anti-citrullinated protein antibodies (ACPAs)] is a hallmark for the diagnosis and prognosis of rheumatoid arthritis (RA) and will also be a useful tool for understanding the fundamental pathologic processes. There are several essential questions pertaining to ACPA that remain to be explored, such as understanding the early specificity of the underlying T-cell recognition, whether the production of ACPA is a primary or secondary process, and in the event of such antibodies being arthritogenic, whether they could possibly regulate the disease development. To answer these questions, animal models are needed, but unfortunately ACPA is not a prominent feature of any of the classical animal models of RA. However, we showed recently that ACPA can be isolated from animals susceptible to collagen-induced arthritis that are specific for citrullinated type II collagen (CII). The citrulline specificity could be visualized, and the specificity is determined primarily by a direct interaction with citrulline. We also demonstrated that these antibodies are specific for the citrullinated epitopes and are pathogenic in vivo. A new hypothesis to explain how inflammation in RA can be directed to cartilaginous joints and be self-perpetuating is suggested, which involves recognition of post-translational modifications (glycosylation and citrullination) on CII by T and B cells that can have both arthritogenic and regulatory consequences.

The calcium-dependent enzyme tissue transglutaminase (tTG) is associated with diverse biological functions, such as induction of apoptosis, modeling of the extracellular matrix, receptor-mediated endocytosis, cell growth and differentiation, cell adhesion and signal transduction. Also, it may deamidate glutamine residues to glutamic acid and catalyze cross-linking of proteins. In this study, we have investigated the impact of tTG for posttranslational modifications and cross-linking of the immunodominant T-cell epitope CII260-270 and their effects on the collagen-induced arthritis, an animal model for rheumatoid arthritis. By using mass spectrometry analysis and hybridoma assays, we have demonstrated that tTG could perform both types of modifications (deamidation and cross-link formation) on the immunodominant T-cell epitope CII259-273. Replacement of the glutamine at position 267 with glutamic acid leads to a decreased binding affinity to MHC II. T cells recognized both non-modfied (Q(267)) and modified (E(267)) CII259-273-peptides. We also show that administration of tTG leads to increased incidence, severity and histopathological manifestations of collagen-induced arthritis in mice. Moreover, we conclude that both processes, deamidation and cross-linking, are involved in the tTG-catalyzed reactions, and in vivo administration of tTG enhances arthritis severity and joint destruction in mice.

Reactive oxygen species (ROS) are important in the immune defense against invading pathogens, but they are also key molecules in the regulation of inflammatory reactions. Low levels of ROS production due to a polymorphism in the neutrophil cytosolic factor 1 (Ncf1) gene are associated with autoimmunity and arthritis severity in mouse models induced with adjuvant. We established an adjuvant-free arthritis model in which disease is induced by injection of the autoantigen collagen type II (CII) and depends on IL-5-producing T cells and eosinophils. In addition, the transgenic expression of mutated mouse CII allowed us to investigate an autoreactive immune response to an autologous Ag and by that natural tolerance mechanism. We show that a deficient ROS production, due to a spontaneous mutation in Ncf1, leads to increased autoantibody production and expansion of IL-33R-expressing T cells, impaired T cell tolerance toward tissue-specific CII, and severe arthritis in this unique model without disturbing adjuvant effects. These results demonstrate that the insufficient production of ROS promotes the breakdown of immune tolerance and development of autoimmune and adjuvant-free arthritis through an IL-5- and IL33R-dependent T cell activation pathway.

For a long time, reactive oxygen species (ROS) produced by the phagocyte NADPH oxidase (NOX2) complex have been considered harmful mediators of inflammation owing to their highly reactive nature. However, there are an increasing number of findings suggesting that ROS produced by the NOX2 complex are anti-inflammatory and prevent autoimmune responses, thus challenging existing dogma. ROS might not only be produced as a mechanism to eradicate invading pathogens, but rather as a means by which to fine-tune the inflammatory response, depending on when, where and at what amounts they are produced. In this review, we aim to describe the current findings highlighting ROS as regulators of autoimmune inflammation, focusing on autoimmune arthritis.

For a long time, genetic studies of complex diseases were most successfully conducted in animal models. However, the field of genetics is now rapidly evolving, and human genetics has also started to produce strong candidate genes for complex diseases. This raises the question of how to continue gene-finding attempts in animals and how to use animal models to enhance our understanding of gene function. In this review we summarize the uses and advantages of animal studies in identification of disease susceptibility genes, focusing on rheumatoid arthritis. We are convinced that animal genetics will remain a valuable tool for the identification and investigation of pathways that lead to disease, well into the future.

Objectives: Autoimmune diseases such as rheumatoid arthritis (RA) and multiple sclerosis (MS) affect a relatively large portion of the population, leading to severe disability if left untreated. Even though pharmaceutics targeting the immune system have revolutionised the therapy of these diseases, there is still a need for novel, more effective therapeutic substances. One such substance is the new chemical entity 9-chloro-2,3 dimethyl-6-(N,N-dimthylamino-2-oxoethyl)-6H-indolo [2,3-b] quionoxaline, Rabeximod, currently being investigated for efficiency in treatment of human RA. In this study we aimed to evaluate Rabeximod as a treatment for autoimmune diseases, using animal models., Methods: In the present investigation we have evaluated Rabeximod as a treatment for autoimmune diseases using mouse models of RA and MS, ie, collagen-induced arthritis, collagen antibody induced arthritis and experimental autoimmune encephalomyelitis., Results: Rabeximod efficiently prevented arthritis and encephalomyelitis in mice. In addition, this effect correlated to the timepoint when cells migrate into the joints., Conclusions: We conclude that Rabeximod reduces disease severity in animal models of autoimmunity and should be considered as a new therapeutic substance for MS and RA.

Introduction: In a cross between two mouse strains, the susceptible B10.RIII (H-2(r)) and resistant RIIIS/J (H-2(r)) strains, a locus on mouse chromosome 5 (Eae39) was previously shown to control experimental autoimmune encephalomyelitis (EAE). Recently, quantitative trait loci (QTL), linked to disease indifferent experimental arthritis models, were mapped to this region. The aim of the present study was to investigate whether genes within Eae39, in addition to EAE, control development of collagen-induced arthritis (CIA)., Methods: CIA, induced by immunisation with bovine type II collagen, was studied in Eae39 congenic and sub-interval congenic mice. Antibody titres were investigated with ELISA.Gene-typing was performed by micro-satellite mapping and statistics was calculated by standard methods., Results: Experiments of CIA in Eae39 congenic- and sub-interval congenic mice, carrying RIIIS/J genes on the B10.RIII genetic background, revealed three loci within Eae39 that control disease and anti-collagen antibody titres. Two of the loci promoted disease and the third locus was protected against CIA development. By further breeding of mice with small congenic fragments, we identified a 3.2 mega base pair (Mbp)interval that regulates disease., Conclusions: Disease-promoting and disease-protecting genes within the Eae39 locus on mouse chromosome 5 control susceptibility to CIA. A disease-protecting locus in the telomeric part of Eae39 results in lower anti-collagen antibody responses. The study shows the importance of breeding sub-congenic mouse strains to reveal genetic effects on complex diseases.

Collagen-induced arthritis (CIA) is a well studied mouse model of the human disease rheumatoid arthritis (RA). Both CIA and RA are complex diseases affected by multiple genes as well as environmental factors. Identifying the genes that determine susceptibility to arthritis would give invaluable clues to the largely unknown aetiology of RA. In this study, we dissected a known locus, Cia6, as well as a genomic region on chromosome 14 with no previously known arthritis loci, using a partial advanced intercross and a collection of congenic strains. The chromosome 14 congenic fragment, containing the T-cell receptor alpha (Tcra) locus, was included based on the hypothesis that the Cia6 locus is caused by a polymorphism in the Tcr beta (Tcrb) locus and that the two loci interact. Splitting up the congenic fragments revealed multiple loci affecting arthritis traits as well as production of collagen-specific autoantibodies. In total seven new loci were identified of which four were in the previously unlinked chromosome 14 region. Both Tcr loci were within CIA loci making them candidate susceptibility genes. The results demonstrate the importance of breaking up genetic regions in smaller fragments to identify the underlying complex set of loci.

Rheumatoid factors (RF), autoantibodies that bind the Fc region of IgG, are one of the major diagnostic marker in rheumatoid arthritis (RA) but occur with lower frequency also in other infectious and inflammatory conditions. Through positional cloning of the previously described quantitative trait locus (QTL) Rf1 in congenic and advanced intercrossed rats, we identified the Ig lambda light chain locus as a locus that regulates the production of RF in rats. The congenic rats produce RF-Ig lambda and have significant higher levels of RF-IgG and RF-IgM in serum, while the DA rat has an impaired RF production and does not produces RF-Ig lambda. Thus, we could investigate the role of RF in pristane-induced arthritis (PIA) as well as ovalbumin-induced airway inflammation. We show that there was no difference in the development and severity of PIA between congenic and parental DA rats, suggesting that RF using lambda light chains have no impact on PIA. However, the RF producing congenic rats developed a more severe airway inflammation as indicated in the significantly increased number of eosinophils in bronchoalveolar lavage fluid as well as total IgE in serum. In addition, RF congenic rats had a significantly enhanced immune response toward OVA due to increased OVA-Igk but not OVA-Igl antibodies, suggesting a possible involvement of RF in the regulation of the humoral immune response.

Previous data have indicated that IL-21 and/or IL-21R are crucial for the differentiation of naïve T cells into Th17 cells and also play a key role in the development of autoimmune disease. Given this, IL-21 and/or IL-21R are potential targets for therapy of such diseases; however, a study in this issue of the European Journal of Immunology, provides a new twist in the story as it is now shown that IL-21 and/or IL-21R play no role in Th17 development or autoimmune inflammatory disease. The reasons for these contradictory data are discussed in this Commentary.

The arthritis-susceptible DA rat is one of the most commonly used rat strains for genetic linkage analysis and is instrumental for the identification of many genetic loci. Even though DA rats were kept as inbred lines at different institutes and suppliers, it became obvious that the various breeding stocks differed genetically. To be able to compare the results from different linkage studies it is very import to verify the genetic background of the substrains used in those studies. We performed a genetic and phenotypic analysis of two DA substrains, DA/ZtmRhd and DA/OlaHsd, and found several genetic differences. One of the allelic differences between the DA/ZtmRhd and the DA/OlaHsd strain was located at rat chromosome 3, a 17-Mb large fragment, including the peak marker of a previously identified quantitative trait locus (QTL) for collagen-induced arthritis, Cia11. In addition, the substrains exhibited a significant difference in the susceptibility to pristane-induced arthritis (PIA) and disease severity of collagen-induced arthritis and PIA. However, by generating and testing a congenic line, we could demonstrate that phenotypic differences were not due to the contaminating fragment on chromosome 3. Nevertheless, we conclude that DA substrains show distinct genetic differences and caution should be taken when comparing arthritis data from different DA substrains.

Neuropathic pain is a common consequence of damage to the nervous system. We here report a genetic analysis of development of neuropathic pain-like behaviors after unilateral photochemically-induced ischemic sciatic nerve injury in a panel of inbred rat strains known to display different susceptibility to autoimmune neuroinflammation. Pain behavior was initially characterized in Dark-Agouti (DA; RT1(av1)), Piebald Virol Glaxo (PVG; RT1(c)), and in the major histocompatibility complex (MHC)-congenic strain PVG-RT1(av1). All strains developed mechanical hypersensitivity (allodynia) following nerve injury. However, the extent and duration of allodynia varied significantly among the strains, with PVG displaying more severe allodynia compared to DA rats. Interestingly, the response of PVG-RT1(avRT1) was similar to that of DA, suggesting regulation by the MHC locus. This notion was subsequently confirmed in an F2 cohort derived from crossing of the PVG and PVG-RT1(av1)strains, where allodynia was reduced in homozygous or heterozygous carriers of the RT1(av1) allele in comparison to rats homozygous for the RT1(c) allele. These results indicate that certain allelic variants of the MHC could influence susceptibility to develop and maintain neuropathic pain-like behavior following peripheral nerve injury in rats.

Autoantibodies developing in humans contribute to the pathogenesis of several diseases, and injected therapeutic antibodies can also trigger adverse side effects. An efficient and rapid elimination of these antibodies are therefore critically needed. Antibody removal by plasmapheresis and immunoadsorption are commonly used methods but have their own limitations. Bacterial enzymes that can cleave IgG molecules or remove carbohydrate moieties to ameliorate their immunogenicity or effector functions in vivo offer new avenues for drug development. Recent discoveries highlight the possibility of cleaving or modifying IgG in vivo by injection of enzymes. Such an approach opens up new therapeutic possibilities not only for the control of pathogenic antibody-mediated inflammatory diseases but also allograft rejection or the treatment of side-effects of 'biologicals' such as monoclonal antibodies.

Reduced capacity to produce ROS increases the severity of T cell-dependent arthritis in both mice and rats with polymorphisms in neutrophil cytosolic factor 1 (Ncf1) (p47phox). Since T cells cannot exert oxidative burst, we hypothesized that T cell responsiveness is downregulated by ROS produced by APCs. Macrophages have the highest burst capacity among APCs, so to study the effect of macrophage ROS on T cell activation, we developed transgenic mice expressing functional Ncf1 restricted to macrophages. Macrophage-restricted expression of functional Ncf1 restored arthritis resistance to the level of that of wild-type mice in a collagen-induced arthritis model but not in a T cell-independent anti-collagen antibody-induced arthritis model. T cell activation was downregulated and skewed toward Th2 in transgenic mice. In vitro, IL-2 production and T cell proliferation were suppressed by macrophage ROS, irrespective of T cell origin. IFN-gamma production, however, was independent of macrophage ROS but dependent on T cell origin. These effects were antigen dependent but not restricted to collagen type II. In conclusion, macrophage-derived ROS play a role in T cell selection, maturation, and differentiation, and also a suppressive role in T cell activation, and thereby mediate protection against autoimmune diseases like arthritis.

Autoimmune diseases such as rheumatoid arthritis (RA) are chronic diseases that cannot be prevented or cured If the pathologic basis of such disease would be known, it might be easier to develop new drugs interfering with critical pathway. Genetic analysis of animal models for autoimmune diseases can result in discovery of proteins and pathways that play key function in pathogenesis, which may provide rationales for new therapeutic strategies. Currently, only the MHC class II is clearly associated with human RA and animal models for RA. However, recent data from rats and mice with a polymorphism in Ncf1, a member of the NADPH oxidase complex, indicate a role for oxidative burst in protection from arthritis. Oxidative burst-activating substances can treat and prevent arthritis in rats, as efficiently as clinically applied drugs, suggesting a novel pathway to a therapeutic target in human RA. Here, the authors discuss the role of oxygen radicals in regulating the immune system and autoimmune disease. It is proposed that reactive oxygen species set the threshold for T cell activation and thereby regulate chronic autoimmune inflammatory diseases like RA. In the light of this new hypothesis, new possibilities for preventive and therapeutic treatment of chronic inflammatory diseases are discussed.

The glycosylation status of IgG has been implicated in the pathology of rheumatoid arthritis. Earlier, we reported the identification of a novel secreted endo-beta-N-acetylglucosaminidase (EndoS), secreted by Streptococcus pyogenes that specifically hydrolyzes the beta-1,4-di-N-acetylchitobiose core of the asparagine-linked glycan of human IgG. Here, we analyzed the arthritogenicity of EndoS-treated collagen type II (CII)-specific mouse mAb in vivo. Endoglycosidase treatment of the antibodies inhibited the induction of arthritis in (BALB/c x B10.Q) F1 mice and induced a milder arthritis in B10.RIII mice as compared with the severe arthritis induced by non-treated antibodies. Furthermore, EndoS treatment did not affect the binding of IgG to CII and their ability to activate complement, but it resulted in reduced IgG binding to FcgammaR and disturbed the formation of stable immune complexes. Hence, the asparagine-linked glycan on IgG plays a crucial role in the development of arthritis.

Apoptotic cells have been reported to down-regulate membrane-bound complement regulatory proteins (m-C-Reg) and to activate complement. Nonetheless, most apoptotic cells do not undergo complement-mediated lysis. Therefore, we hypothesized that fluid phase complement inhibitors would bind to apoptotic cells and compensate functionally for the loss of m-C-Reg. We observed that m-C-Reg are down-regulated rapidly upon apoptosis but that complement activation follows only after a gap of several hours. Coinciding with, but independent from, complement activation, fluid phase complement inhibitors C4b-binding protein (C4BP) and factor H (fH) bind to the cells. C4BP and fH do not entirely prevent complement activation but strongly limit C3 and C9 deposition. Late apoptotic cells, present in blood of healthy controls and systemic lupus erythematosus patients, are also positive for C4BP and fH. Upon culture, the percentage of late apoptotic cells increases, paralleled by increased C4BP binding. C4BP binds to dead cells mainly via phosphatidylserine, whereas fH binds via multiple interactions with CRP playing no major role for binding of C4BP or fH. In conclusion, during late apoptosis, cells acquire fluid phase complement inhibitors that compensate for the down-regulation of m-C-Reg and protect against excessive complement activation and lysis.

The view on reactive oxygen species (ROS) in inflammation is currently shifting from being considered damaging toward having a more complex role in regulating inflammatory reactions. We recently demonstrated a role of ROS in regulation of animal models for the autoimmune disease rheumatoid arthritis. Low levels of ROS production, due to a mutation in the Ncf1 gene coding for the Ncf1 (alias p47(phox)) subunit of the NADPH oxidase complex, was shown to be associated with increased autoimmunity and arthritis severity in both rats and mice. To further investigate the role of ROS in autoimmunity, we studied transgenic mice expressing collagen type II (CII) with a mutation (D266E) in the immunodominant epitope that mimics the rat and human CII (i.e., mutated mouse collagen or MMC). This mutation results in a stronger binding of the epitope to the MHC class II molecule and leads to more pronounced tolerance and resistance to arthritis induced with rat CII. When the Ncf1 mutation was bred into these mice, tolerance was broken, resulting in enhanced T cell autoreactivity, high titers of anti-CII Abs, and development of severe arthritis. These findings highlight the importance of a sufficient ROS production in maintenance of tolerance to self-Ags, a central mechanism in autoimmune diseases such as rheumatoid arthritis. This is important as we, for the first time, can follow the effect of ROS on molecular mechanisms where T cells are responsible for either protection or promotion of arthritis depending on the level of oxygen species produced.

Positional cloning of the underlying genes for the rare syndrome autoimmune polyendocrinopathy candidadiasis extrodermal dystrophy (APECED) opened a new venue of research on the role of central tolerance in autoimmunity. The associated autoimmune regulator gene (AIRE), was found to be expressed in medullary thymus epithelial cells (mTEC) in both man and mice, and to control promiscuous expression of sets of self antigens. The lack of AIRE in both mice and man led to the development of a quite specific, but also an inter-individual variable, set of autoimmune and infectious diseases. An article in this issue of the European Journal of Immunology demonstrates that several autoantigens controlled by AIRE are variably expressed in different human individuals. Most importantly it is shown that carriers of the type 1 diabetes (T1D) associated locus IDDM2 show lower expression of insulin in mTEC, as controlled by AIRE. The genetic variability of autoantigen expression in the thymus thus seems to determine the variable predisposition to autoimmunity.

Linkage analysis of F(2) crosses has led to identification of large numbers of quantitative trait loci (QTL) for complex diseases, but identification of the underlying genes has been more difficult. Reasons for this could be complications that arise from separation of interacting or neighboring loci. We made a partial advanced intercross (PAI) to characterize and fine-map linkage to collagen-induced arthritis in two chromosomal regions derived from the DBA/1 strain and crossed into the B10.Q strain: Cia7 on chromosome 7 and a locus on chromosome 15. Only Cia7 was detected by a previous F(2) cross. Linkage analysis of the PAI revealed a different linkage pattern than the F(2) cross, adding multiple loci and strong linkage to the previously unlinked chromosome 15 region. Subcongenic strains derived from animals in the PAI confirmed the loci and revealed additional subloci. In total, no less than seven new loci were identified. Several loci interacted and three loci were protective, thus partly balancing the effect of the disease-promoting loci. Our results indicate that F(2) crosses do not reveal the full complexity of identified QTLs, and that detection is more dependent on the genetic context of a QTL than the potential effect of the underlying gene.

Eosinophilia is a characteristic feature of many inflammatory diseases including inflammatory bowel disease and asthma. It also occurs in a subtype of rheumatoid arthritis but the role of eosinophils has been unclear and animal models have been lacking. Here, we introduce a new mouse model to study the role of eosinophilia in arthritis. Intraperitoneal injection of type II collagen alone, without any adjuvant, was sufficient to induce chronic arthritis in a mouse with transgenic T cells specific for type II collagen. The arthritis was accompanied by infiltration of eosinophils into the synovial tissue and the disease could be blocked with neutralizing anti-IL-5 antibodies. To our knowledge, this is the first description of an eosinophilic disease form of destructive arthritis.

Complex traits, including inflammatory rheumatic diseases, have important genetic features, but most of the responsible genes have not been conclusively identified. Genetic analysis of inbred animal models and comparative genetics--the comparison of genes between different species--might help to identify the crucial genes and to investigate more directly the biology involved. Genome-wide linkage analysis of particular genes can be assessed by genetic segregation studies, whereas disease pathways can be delineated by the use of congenic strains. To clone disease genes, the traits need to be transformed so that they are inherited in a more Mendelian manner: achieving this pattern requires isolation of the locus on a genetic background that allows high penetrance by minimization of the size of congenic fragments, genetic manipulations without associated artifacts, or identification of highly penetrant mutations by phenotypic selection. Although almost one hundred quantitative trait loci for arthritis have been identified, only a few genes have so far been positionally cloned. In this Review we highlight the possibilities of using animal models to identify genes associated with complex diseases like arthritis, illustrated with available findings for genes such as those encoding major histocompatibility complex class II, neutrophil cytosolic factor 1 (Ncf1/p47(phox)) and ZAP70.

Rheumatoid arthritis (RA) is a chronic inflammatory disease with a heritability of 60%. Genetic contributions to RA are made by multiple genes, but only a few gene associations have yet been confirmed. By studying animal models, reduced capacity of the NADPH-oxidase (NOX) complex, caused by a single nucleotide polymorphism (SNP) in one of its components (the NCF1 gene), has been found to increase severity of arthritis. To our knowledge, however, no studies investigating the potential role played by reduced reactive oxygen species production in human RA have yet been reported. In order to examine the role played by the NOX complex in RA, we investigated the association of 51 SNPs in five genes of the NOX complex (CYBB, CYBA, NCF4, NCF2, and RAC2) in a Swedish case-control cohort consisting of 1,842 RA cases and 1,038 control individuals. Several SNPs were found to be mildly associated in men in NCF4 (rs729749, P = 0.001), NCF2 (rs789181, P = 0.02) and RAC2 (rs1476002, P = 0.05). No associations were detected in CYBA or CYBB. By stratifying for autoantibody status, we identified a strong association for rs729749 (in NCF4) in autoantibody negative disease, with the strongest association detected in rheumatoid factor negative men (CT genotype versus CC genotype: odds ratio 0.34, 95% confidence interval 0.2 to 0.6; P = 0.0001). To our knowledge, this is the first genetic association identified between RA and the NOX complex, and it supports previous findings from animal models of the importance of reactive oxygen species production capacity to the development of arthritis.

The therapeutic effect of monoclonal antibody (H57-597 MoAb) against T-cell receptor (TCR) alphabeta has been investigated on MOG(35-55)-induced experimental autoimmune encephalomyelitis (EAE), as a model system for T-cell-mediated chronic inflammation in the central nervous system (CNS). Short-term administration of the anti-TCR alphabeta immediately after immunization protected the mice from EAE. Furthermore, anti-TCR alphabeta treatment on an established disease restored the self-tolerance which led to a complete remission of EAE and a dramatic reduction of inflammatory cells in the CNS, while treatment with control antibody (hamster IgG) was ineffective. The remission was durable and not associated with disappearance of autoreactive T cells as measured by persistence of MOG-reactive T-cell proliferation in vitro. However, MOG-reactive T cells from anti-TCR-treated animals produced significantly lower amounts of inflammatory TNF-alpha and IFN-gamma. In addition, while a transient deletion of CD4(+) and CD8(+) T cells was observed, a population of T cells expressing CD3, NK1.1 and CD69 (NKT cells) were expanding. By transfer of spleen cells from anti-TCR MoAb-treated animals, we could show that the tolerogenic capacity can be transferred to untreated recipients with EAE. The data indicate therapeutic effect of anti-TCR alphabeta MoAb (H57-597), which represents a promising approach in treatment of T-cell-mediated autoimmune diseases.

Rheumatoid arthritis (RA) is a description of classical symptoms that can be grouped together to be recognized as a common entity. However, the disease is more heterogeneous and is likely composed of many different, distinct diseases. This heterogeneity is of two types. First, the disease can be classified into several subtypes, and second, the underlying cause of each disease group may be attributable to different genetic and environmental factors, each contributing to a distinct disease phenotype. This is an important starting point when discussing animal models for RA. Thus, there is not one model for RA. There are, and must be, several different models with different symptoms and different pathogenic mechanisms, controlled by different genes.

Type XI collagen (CXI) and cartilage oligomeric matrix protein (COMP) are minor components in cartilage, shown to be arthritogenic. CXI is a heterotrimeric triple helical fibrillar collagen and intermingled in the collagen fibers with type II (CII). COMP is the major noncollagenous protein of cartilage and is a homopentamer, interacting with the collagen fibers with each of its subunits. Similar to CII, homologous rat CXI also induces a chronic arthritis in rats but with a different major histocompatibility complex (MHC) genetic control and pathogenesis. CXI induced arthritis (C(XI)IA) is characterized by a more pronounced chronic relapsing disease course. The MHC allele of importance is the RT1f haplotype and, surprisingly, some of the CII associated MHC alleles like RT1a are less permissive. Immunization with COMP induces a severe but self-limited arthritis in strains with a genetic background resistant to most other forms of arthritis or even autoimmune models, the E3 rat. The MHC association also differs between the different models (CIA, CXI, and COMPIA). An autoimmune response to COMP is triggered despite the circulation of COMP fragments in both physiologic and arthritic states. The induction of arthritis in rats with CXI or COMP provides an arthritis models with a distinct pathogenesis as compared with other induced arthritis models.

A chronic relapsing arthritis develops after a single subcutaneous injection of small amounts of pristane; the pristane induced arthritis (PIA) model in the rat. PIA is characterized by a sudden onset of disease 2 wk after induction. The main pathological features of PIA include edema accompanied by an acute phase response, infiltration into the joint of mononuclear and polymorphonuclear cells, pannus formation, and erosion of cartilage and bone. PIA is a disease that is largely T-cell dependent that can be adoptively transferred by activated CD4+ T-cells. PIA in rats is followed clinically by macroscopic scoring and is characterized by an early acute phase of severe inflammation after onset that eventually gradually disappears to be followed by less severe relapsing phases of new inflamed joints and increasing cartilage erosion and joint deformity. PIA can be diagnosed by biochemical analyzes in plasma that reflects systemic inflammation (alpha1-acid glycoprotein (AGP) and IL-6) and cartilage erosion (COMP).

Rheumatoid arthritis (RA) is a polygenic and multifactorial disease. Many complex immunological and genetic interactions are involved in the final out come of the clinical disease. To understand the various disease pathways operating during the disease course, we need many different animal models. Collagen induced arthritis (CIA) is one of the widely used animal models sharing many pathological and histological similarities with RA and antibodies play an important role in the inflammatory phase of CIA. This chapter describes, in detail, an animal model for arthritis using CII specific monoclonal antibodies, the so-called collagen antibody induced arthritis (CAIA), which shares many characteristics of CIA. CAIA model provides an opportunity to study the inflammatory phase of arthritis without involving the priming phase of the immune response. CAIA can be used for not only studying inflammatory processes in arthritis and screening drug candidates controlling joint inflammatory phase but also as a model for studying common mechanisms involved in many antibody mediated diseases.

Genetic segregation analysis between NOD and C57BL strains have been used to identify loci associated with autoimmune disease. Only two loci (Cia2 and Cia9) had earlier been found to control development of arthritis, whereas none of the previously identified diabetes loci was of significance for arthritis. We have now made a high-powered analysis of a backcross of NOD genes on to the B10.Q strain for association with collagen-induced arthritis. We could confirm relevance of both Cia2 and Cia9 as well as the interaction between them, but we did not identify any other significant arthritis loci. Immune cellular subtyping revealed that Cia2 was also associated with the number of blood macrophages. Congenic strains of the Cia2 and Cia9 loci on the B10.Q background were made and used to establish a partial advanced intercross (PAI). Testing the PAI mice for development of collagen-induced arthritis confirmed the loci and the interactions and also indicated that at least two genes contribute to the Cia9 locus. Furthermore, it clearly showed that Cia2 is dominant protective but that the protection is not complete. Because these results may indicate that the Cia2 effect on arthritis is not only due to the deficiency of the complement C5, we analyzed complement functions in the Cia2 congenics as well as the PAI mice. These data show that not only arthritis but also C5-dependent complement activity is dominantly suppressed, confirming that C5 is one of the major genes explaining the Cia2 effect.

Background: Despite recent successes with biological agents as therapy for autoimmune inflammatory diseases such as rheumatoid arthritis (RA), many patients fail to respond adequately to these treatments, making a continued search for new therapies extremely important. Recently, the prevailing hypothesis that reactive oxygen species (ROS) promote inflammation was challenged when polymorphisms in Ncf1, that decrease oxidative burst, were shown to increase disease severity in mouse and rat arthritis models. Based on these findings we developed a new therapy for arthritis using oxidative burst-inducing substances., Methods and Findings: Treatment of rats with phytol (3,7,11,15-tetramethyl-2-hexadecene-1-ol) increased oxidative burst in vivo and thereby corrected the effect of the genetic polymorphism in arthritis-prone Ncf1(DA) rats. Importantly, phytol treatment also decreased the autoimmune response and ameliorated both the acute and chronic phases of arthritis. When compared to standard therapies for RA, anti-tumour necrosis factor-alpha and methotrexate, phytol showed equally good or better therapeutic properties. Finally, phytol mediated its effect within hours of administration and involved modulation of T cell activation, as injection prevented adoptive transfer of disease with arthritogenic T cells., Conclusions: Treatment of arthritis with ROS-promoting substances such as phytol targets a newly discovered pathway leading to autoimmune inflammatory disease and introduces a novel class of therapeutics for treatment of RA and possibly other chronic inflammatory diseases.

Rats and mice with a lower capacity to produce reactive oxygen species (ROS) because of allelic polymorphisms in the Ncf1 gene (which encodes neutrophil cytosolic factor 1) are more susceptible to develop severe arthritis. These data suggest that ROS are involved in regulating the immune response. We now show that the lower capacity to produce ROS is associated with an increased number of reduced thiol groups (-SH) on T cell membrane surfaces. Artificially increasing the number of reduced thiols on T cells from animals with arthritis-protective Ncf1 alleles by glutathione treatment lowered the threshold for T cell reactivity and enhanced proliferative responses in vitro and in vivo. Importantly, T cells from immunized congenic rats with an E3-derived Ncf1 allele (DA.Ncf1E3 rats) that cannot transfer arthritis to rats with an arthritis-associated Dark Agouti (DA)-derived mutated Ncf1 allele (DA.Ncf1DA rats) became arthritogenic after increasing cell surface thiol levels. This finding was confirmed by the reverse experiment, in which oxidized T cells from DA.Ncf1DA rats induced less severe arthritis compared with controls. Therefore, we conclude that ROS production as controlled by Ncf1 is important in regulating surface redox levels of T cells and thereby suppresses autoreactivity and arthritis development.

It is widely believed that IL-4 exerts its influence by profiling the immune response during priming and expansion of immune cells, and thereby modulates the outcome of chronic inflammation. In the present investigation, collagen antibody-induced arthritis (CAIA) was used to delineate the role of IL-4 in a T cell-independent inflammatory phase. Mice predisposed to Th2 cytokines (BALB/c and STAT4-deficient mice) developed a more severe arthritis than mice biased towards Th1 cytokines (C57BL/6 and STAT6-deficient mice). Reduced incidence of CAIA was observed in IL-4-deficient mice compared to control littermates. Infiltrating cells in the paws of IL-4-sufficient mice had increased osteoclast activity and tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta secretion. Massive infiltration of granulocytes and joint and cartilage damage were present in arthritic paws. Depletion of IL-4 suppressed CAIA, which was abrogated by IFN-gamma neutralization. IL-1R- and IL-1RTNFR-deficient mice were completely resistant to CAIA. Thus, IL-4 promotes an antibody-mediated and TNF-alpha/IL-1beta-dependent inflammation in vivo.

Rheumatoid arthritis (RA) is a chronic inflammatory disease directed towards peripheral joints. As all common diseases it is associated with several genes and a multitude of environmental factors. In addition, in similarity with most other complex diseases, it is defined only on the basis of clinical signs and symptoms, it is therefore more properly classified as a syndrome rather than a distinct disease entity. This complexity of RA has led to difficulties in finding the underlying genes. In spite of large efforts it is still only the MHC class II region that reaches genome wide significance in confirmed studies. However, this has been known for decades and we are still unable to conclusively identify the underlying gene/s. We hypothesize that an MHC class II gene is involved and although we have detailed knowledge on both structure and function we do not know its possible pathogenic role in RA. In this review I will argue for the usefulness of animal models as a tool to identify genes and pathways associated with disease. The examples to be discussed are genes controlling the oxidative burst pathways and MHC class II genes.

In both collagen-induced arthritis (CIA) and rheumatoid arthritis, T cells recognize a galactosylated peptide from type II collagen (CII). In this study, we demonstrate that the CII259-273 peptide, galactosylated at lysine 264, in complex with Aq molecules prevented development of CIA in mice and ameliorated chronic relapsing disease. In contrast, nonglycosylated CII259-273/Aq complexes had no such effect. CIA dependent on other MHC class II molecules (Ar/Er) was also down-regulated, indicating a bystander vaccination effect. T cells could transfer the amelioration of CIA, showing that the protection is an active process. Thus, a complex between MHC class II molecules and a posttranslationally modified peptide offers a new possibility for treatment of chronically active autoimmune inflammation such as rheumatoid arthritis.

Pristane-induced arthritis (PIA) in rats, a model for rheumatoid arthritis (RA), is a T cell-dependent disease. However, pristane itself is a lipid and unable to form a stable complex with a MHC class II molecule. Therefore, the specificity and function of the T cells in PIA are as unclear as in rheumatoid arthritis. In this study, we show that activated CD4+ alphabetaT cells, which target peripheral joints, transfer PIA. The pristane-primed T cells are of oligo or polyclonal origin as determined by their arthritogenicity after stimulation with several mitogenic anti-TCRVbeta and anti-TCRValpha mAbs. Arthritogenic cells secreted IFN-gamma and TNF-alpha (but not IL-4) when stimulated with Con A in vitro, and pretreatments of recipient rats with either anti-IFN-gamma or a recombinant TNF-alpha receptor before transfer ameliorated arthritis development. Most importantly, we show that these T cells are MHC class II restricted, because treatment with Abs against either DQ or DR molecules ameliorates arthritis development. The MHC class II restriction was confirmed by transferring donor T cells to irradiated recipients that were syngenic, semiallogenic, or allogenic to MHC class II molecules, in which only syngenic and semiallogenic recipients developed arthritis. These data suggest that the in vivo administration of a non-antigenic adjuvant, like pristane, activates CD4+ alphabetaT cells that are MHC class II restricted and arthritogenic.

It has so far been difficult to identify genes behind polygenic autoimmune diseases such as rheumatoid arthritis (RA), multiple sclerosis (MS), and type I diabetes (T1D). With proper animal models, some of the complexity behind these diseases can be reduced. The use of linkage analysis and positional cloning of genes in animal models for RA resulted in the identification of one of the genes regulating severity of arthritis in rats and mice, the Ncf1 gene. The Ncf1 gene encodes for the Ncf1 protein that is involved in production of free oxygen radicals through the NADPH oxidase complex, which opens up a new pathway for therapeutic treatment of inflammatory diseases. In most cases, however, a quantitative trait locus (QTL) is the sum effect of several genes within and outside the QTL, which make positional cloning difficult. Here we will discuss the possibilities and difficulties of gene identification in animal models of autoimmune disorders.

Joint cartilage is attacked in both autoimmune inflammatory and osteoarthritic processes. Type IX collagen (CIX) is a protein of importance for cartilage integrity and stability. In this study we have backcrossed a transgenic disruption of the col9a1 gene, which leads to an absence of CIX, into two different inbred mouse strains, DBA/1 and B10.Q. None of the CIX-deficient mice developed observable clinical or microscopic osteoarthritis, but DBA/1 male mice had more pronounced enthesopathic arthritis, the so-called stress-induced arthritis. Both DBA/1 and B10.Q strains are susceptible to the induction of collagen-induced arthritis, and CIX deficiency in both strains led to the development of a more severe arthritis than in the controls. Induction of arthritis with monoclonal antibodies against type II collagen (CII) led to an earlier arthritis in the paws that also involved the knee joints. The antibodies used, which were specific for the J1 and the C1I epitopes of CII, initiate their arthritogenic attack by binding to cartilage. The C1I-specific antibodies bound to cartilage better in CIX-deficient mice than in wild-type animals, demonstrating that the lack of CIX in cartilage leads to an increased accessibility of structures for antibody binding and thus making the joints more vulnerable to inflammatory attack. These findings accentuate the importance of cartilage stability; cartilage disrupted as a result of genetic disorders could be more accessible and vulnerable to an autoimmune attack by pathogenic antibodies.

Inflammation is a physiological response that may go uncontrolled and thereby develop in a chronic way. This seems to happen in many common diseases of autoimmune, degenerative, or allergic character. Rheumatoid arthritis (RA) is by definition a chronic disease with an autoimmune inflammatory attack on diarthrodial cartilaginous joints. The development of new treatment neutralizing cytokines involved in the inflammatory attack has given relief and gives the promise of more effective treatment of already established disease. It is now time to set our eyes on a new vision to develop preventive and curative treatment based on knowledge of the unique and causative pathogenic mechanisms. To do this we believe it is important to identify the natural-selected polymorphisms that are associated with disease. These have proven to be extremely difficult to identify in complex diseases such as RA, but using animal models, this work is closer to reality. Animal models have recently been developed mimicking various aspects of the human disease. We will present an example in which a genetic polymorphism associated with the development of arthritis has been identified. On the basis of this finding, a new pathway involving control of immune tolerance by reactive oxidative species has been identified and a new class of antiinflammatory agents activating the induced oxidative burst protein complex is suggested.

During the development of rheumatoid arthritis (RA) autoantibodies to IgG-Fc, citrullinated proteins, collagen type II (CII), glucose 6 phosphoisomerase (G6PI) and some other self-antigens appear. Of these, a pathogenic effect of the anti-CII and anti-G6PI antibodies is well demonstrated using animal models. These new antibody mediated arthritis models have proven to be very useful for studies involved in understanding the molecular pathways of the induction of arthritis in joints. Both the complement and FcgammaR systems have been found to play essential roles. Neutrophils and macrophages are important inflammatory cells and the secretion of tumour necrosis factor-alpha and IL-1beta is pathogenic. The identification of the genetic polymorphisms predisposing to arthritis is important for understanding the complexity of arthritis. Disease mechanisms and gene regions studied using the two antibody-induced arthritis mouse models (collagen antibody-induced arthritis and serum transfer-induced arthritis) are compared and discussed for their relevance in RA pathogenesis.

A 25-year-old, with type I Diabetes Mellitus with a previous diagnosis of Protamine Allergy but not to human Insulin, started to notice anaphylactic reactions immediately after bolus with Insulin. Skin prick and intradermal test were positive to all insulins. Skin tests to other potential allergens resulted negative. Examination after bolus of Human Insulin revealed urticaria. Daily insulin requirement were around 2-2,4 U/Kg/day. Slow desensitisation with Aspart insulin, the insulin with lowest size of skin test, was performed using subcutaneous insulin pump. Six months after the end of desensitisation his daily insulin requirement decreased to 0.8 U/Kg/day and oral corticosteroids are being reduced with no symptoms.

Although monoclonal antibody (mAb)-mediated immunotherapy of cancer has been proven to be feasible for clinical use, success rates until now have been disappointing. One reason for this might be the overexpression of membrane-bound complement regulatory proteins (mCRPs) by tumour cells. As complement activation is an important effector mechanism induced by therapeutic mAbs, inhibition of complement activation by tumour cells might reduce therapeutic efficacy by decreasing direct complement-mediated lysis as well as complement-dependent cellular cytotoxicity. Modulation of the function of these mCRPs might be achieved with therapeutic bispecific (bi-)mAbs that target a tumour antigen and simultaneously block a major mCRP. Clinical results will probably increase with such bi-mAbs compared with monovalent antitumour mAbs. In this review the feasibility of this approach is discussed.

Objective: Clinical trials using interferon-beta (IFNbeta) in the treatment of rheumatoid arthritis have shown conflicting results. We undertook this study to understand the mechanisms of IFNbeta in arthritis at a physiologic level., Methods: Collagen-induced arthritis (CIA) was induced in IFNbeta-deficient and control mice. The role of IFNbeta was investigated in both the priming and effector phases of the disease. The effect of IFNbeta deficiency on synovial cells, macrophages, and fibroblasts from preimmunized mice was analyzed by flow cytometry, immunohistochemistry, and enzyme-linked immunosorbent assay. Differences in osteoclast maturation were determined in situ by histology of arthritic and naive paws and by in vitro maturation studies of naive bone marrow cells. The importance of IFNbeta-producing fibroblasts was determined by transferring fibroblasts into mice at the time of CIA immunization., Results: Mice lacking IFNbeta had a prolonged disease with a higher incidence compared with control mice. IFNbeta deficiency was found to influence the effector phase, but not the priming phase, of arthritis. Compared with control mice, IFNbeta-deficient mice had greater infiltration of CD11b+ cells and greater production of tumor necrosis factor alpha in vivo, and their macrophages and fibroblasts were both more activated in vitro. Moreover, IFNbeta-deficient mice generated a greater number of osteoclasts in vitro, and mice immunized to induce arthritis, but not naive mice, had a greater number of osteoclasts in vivo compared with control mice. Importantly, IFNbeta-competent fibroblasts were able to ameliorate arthritis in IFNbeta-deficient recipients., Conclusion: Our data indicate that IFNbeta is involved in regulating the activation state of osteoclasts and stromal cells, including macrophages and fibroblasts, but that it has little effect on T cells.

One of the major quantitative trait loci (QTLs) associated with arthritis in crosses between B10.RIII and RIIIS/J mice is the Cia5 on chromosome 3. Early in the congenic mapping process it was clear that the locus was complex, consisting of several subloci with small effects. Therefore, we developed two novel strategies to dissect a QTL: the partial advanced inter-cross (PAI) strategy, with which we recently found the Cia5 region to consist of three loci, Cia5, Cia21 and Cia22, and now we introduce the QTL-chip strategy, where we have combined congenic mapping with a QTL-restricted expression profiling using a novel microarray design. The expression of QTL genes was compared between parental and congenic mice in lymph node, spleen and paw samples in five biological replicates and in dye-swapped experiments at three time points during the induction phase of arthritis. The QTL chip approach revealed 4 genes located in Cia21, differently expressed in lymph nodes, and 14 genes in Cia22, located within two clusters. One cluster contains six genes, differently expressed in spleen, and the second cluster contains eight genes, differently expressed in paws. We conclude the QTL-chip strategy to be valuable in the selection of candidate genes to be prioritized for further investigation., (Genes and Immunity (2005) 6, 575-583. doi:10.1038/sj.gene.6364242; published online 14 July 2005.)

An antibody response to defined epitopes located on the triple helical portion of type II collagen (CII) is associated with the development of collagen-induced arthritis (CIA) and rheumatoid arthritis (RA). Monoclonal antibodies to epitopes associated with arthritis, but not antibodies specific for epitopes not associated with arthritis, induce arthritis in mice, the so-called collagen antibody induced arthritis (CAIA) model. We have selected monoclonal IgG antibodies specific for four well-defined major epitopes on triple helical CII, the C1, J1, D3 and U1 epitopes. These antibodies bind the epitopes specifically as determined using recombinant or synthetic triple helical epitopes. They are encoded from somatically mutated V genes. They all bind cartilage in vivo in normal mice. All of the antibodies induce mild arthritis after injection intravenously and if injected as a cocktail they induce severe clinical arthritis. Intravenous injection of a total of 4 mg antibodies (0.5 mg antibodies per clone) induced arthritis in several different mouse strains without any secondary immune stimulus and intraperitoneal injection of LPS 7 days later dramatically raised the severity. Thus, this method is recommended as a new protocol for the induction of CAIA.

Collagen-induced arthritis is a mouse model of rheumatoid arthritis (RA) and is commonly induced after immunization with type II collagen (CII) of a non-mouse origin. T cell recognition of heterologous CII epitopes has been shown to be critical in development of arthritis, as mice with cartilage-restricted transgenic expression of the heterologous T cell epitope (MMC mice) are partially tolerized to CII. However, the mechanism responsible for tolerance and arthritis resistance in these mice is unclear. The present study investigated the regulatory mechanisms in naturally occurring self-tolerance in MMC mice. We found that expression of heterologous rat CII sequence in the cartilage of mice positively selects autoreactive CD4(+) T cells with suppressive capacity. Although CD4(+)CD25(+) cells did not play a prominent role in this suppression, CD152-expressing T cells played a crucial role in this tolerance. MMC CD4(+) T cells were able to suppress proliferation of wild-type cells in vitro where this suppression required cell-to-cell contact. The suppressive capability of MMC cells was also demonstrated in vivo, as transfer of such cells into wild-type arthritis susceptible mice delayed arthritis onset. This study also determined that both tolerance and disease resistance were CD152-dependent as demonstrated by Ab treatment experiments. These findings could have relevance for RA because the transgenic mice used express the same CII epitope in cartilage as humans and because autoreactive T cells, specific for this epitope, are present in transgenic mice as well as in patients with RA.

Development of autoimmune disease is the result of activation of the immune system that subsequently leads to tissue destruction. Although the clinical outcome significantly differs between autoimmune diseases, some pathogenic pathways could be shared. During the recent years, intense efforts to find the genetic factors behind development of the complex and polygenic autoimmune diseases have been undertaken. The difficulties in addressing what genetic factors predispose for autoimmunity in humans underline the importance of animal models in the understanding of the general mechanisms behind the initiation of disease. Interestingly, it has been observed in studies of experimental models of autoimmune diseases, that many of the genetic linkages to disease development are located in the same genetic regions and potentially could be controlled by the same gene. Furthermore, comparison of the mouse/rat genetic regions with regions of association to human inflammatory diseases, also demonstrates some homologous loci between species. Some mouse strains can develop disease in more than one model for autoimmunity. This not only argues for some general mechanisms, but it also supports mechanisms related to the specific tissues attacked in the various autoimmune diseases. Here, we will discuss some aspects of shared autoimmunity in mouse models from a genetic point of view.

Identification of genes controlling complex diseases has proven to be difficult; however, animal models may pave the way to determine how low penetrant genes interact to promote disease development. We have dissected the Cia5/Eae3 susceptibility locus on mouse chromosome 3 previously identified to control disease in experimental models of multiple sclerosis and rheumatoid arthritis. Congenic strains showed significant but small effects on severity of both diseases. To improve the penetrance, we have now used a new strategy that defines the genetic interactions. The QTL interacted with another locus on chromosome 15 and a partial advanced intercross breeding of the two congenic strains for eight generations accumulated enough statistical power to identify interactions with several loci on chromosome 15. Thereby, three separate loci within the original QTL could be identified; Cia5 affected the onset of arthritis by an additive interaction with Cia31 on chromosome 15, whereas the Cia21 and Cia22 affected severity during the chronic phase of the disease through an epistatic interaction with Cia32 on chromosome 15. The definition of genetic interactions was a prerequisite to dissect the Cia5 QTL and we suggest the partial advanced intercross strategy to be helpful also for dissecting other QTL controlling complex phenotypes.