Genetics of susceptibility to chronic experimental encephalomyelitis and arthritis

Cystatin C influences the autoimmune but not inflammatory response to cartilage type II collagen leading to chronic arthritis development

Introduction

Collagen-induced arthritis (CIA) is a mouse model for rheumatoid arthritis (RA) and is induced after immunization with type II collagen (CII). CIA, like RA, is an autoimmune disease leading to destruction of cartilage and joints, and both the priming and inflammatory phases have been suggested to be dependent on proteases. In particular, the cysteine proteases have been proposed to be detrimental to the arthritic process and even immunomodulatory. A natural inhibitor of cysteine proteases is cystatin C.

Methods

Cystatin C-deficient, sufficient and heterozygous mice were tested for onset, incidence and severity of CIA. The effect of cystatin C-deficiency was further dissected by testing the inflammatory effector phase of CIA; that is, collagen antibody-induced arthritis model and priming phase, that is, T cell response both in vivo and in vitro. In addition, in order to determine the importance of T cells and antigen-presenting cells (APCs), these cell populations were separated and in vitro T cell responses determined in a mixed co-culture system. Finally, flow cytometry was used in order to further characterize cell populations in cystatin C-deficient mice.

Results

Here, we show that mice lacking cystatin C, develop arthritis at a higher incidence and an earlier onset than wild-type controls. Interestingly, when the inflammatory phase of CIA was examined independently from immune priming then cystatin C-deficiency did not enhance the arthritis profile. However, in line with the enhanced CIA, there was an increased T cell and B cell response as delayed-type hypersensitivity reaction and anti-CII antibody titers were elevated in the cystatin C-deficient mice after immunization. In addition, the ex vivo naïve APCs from cystatin C-deficient mice had a greater capacity to stimulate T cells. Interestingly, dendritic cells had a more activated phenotype in naïve cystatin C-deficient mice.

Conclusions

The lack of cystatin C enhances CIA and primarily affects in vivo priming of the immune system. Although the mechanism of this is still unknown, we show evidence for a more activated APC compartment, which would elevate the autoimmune response towards CII, thus resulting in an enhanced development of chronic arthritis.

Endogenous collagen peptide activation of CD1d-restricted NKT cells ameliorates tissue-specific inflammation in mice

NKT cells in the mouse recognize antigen in the context of the MHC class I-like molecule CD1d and play an important role in peripheral tolerance and protection against autoimmune and other diseases. NKT cells are usually activated by CD1d-presented lipid antigens. However, peptide recognition in the context of CD1 has also been documented, although no self-peptide ligands have been reported to date. Here, we have identified an endogenous peptide that is presented by CD1d to activate mouse NKT cells. This peptide, the immunodominant epitope from mouse collagen type II (mCII707-721), was not associated with either MHC class I or II. Activation of CD1d-restricted mCII707-721-specific NKT cells was induced via TCR signaling and classical costimulation. In addition, mCII707-721-specific NKT cells induced T cell death through Fas/FasL, in an IL-17A-independent fashion. Moreover, mCII707-721-specific NKT cells suppressed a range of in vivo inflammatory conditions, including delayed-type hypersensitivity, antigen-induced airway inflammation, collagen-induced arthritis, and EAE, which were all ameliorated by mCII707-721 vaccination. The findings presented here offer new insight into the intrinsic roles of NKT cells in health and disease. Given the results, endogenous collagen peptide activators of NKT cells may offer promise as novel therapeutics in tissue-specific autoimmune and inflammatory diseases.

The novel small molecule drug Rabeximod is effective in reducing disease severity of mouse models of autoimmune disorders

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.

The role of collagen antibodies in mediating arthritis

This review examines evidence that rheumatoid arthritis (RA) depends on autoimmunity to articular collagen, and mechanisms whereby autoantibodies to type II collagen contribute to disease development. Three major autoantigenic reactants have been identified in RA; the corresponding autoantibodies are rheumatoid factor (RF), antibodies to citrullinated peptide antigens (ACPA), citrullinated peptides (anti-CCP), and anti-type II collagen (anti-CII). Both RF and ACPA are well-validated and predictive markers of severe erosive RA, but cannot be linked to pathogenesis. By contrast, in various animal species immunized with CII there occurs an erosive inflammatory arthritis resembling that seen in human RA, together with antibodies to CII with an epitope specificity similar to that in RA. We discuss the well-known role of immune complexes in the induction of inflammation within the joint, and present recent data showing, additionally, that antibodies to CII cause direct damage to cartilage in vitro. The close resemblances between human RA and collagen-induced arthritis in animals suggest that autoimmunity, and particularly autoantibodies to CII, are important for both the initiation and perpetuation of RA in a dual manner: as contributors to the inflammation associated with immune complex deposition, and as agents with direct degradative effects on cartilage integrity and its repair.

Preclinical models of arthritic disease in non-human primates

The costs for the development of new drugs have increased dramatically over the past 30 years. One of the main reasons for this increase is the low success rate of new drugs being approved for patient use, which is, in part, a consequence of the common use of rodent models for preclinical validation of efficacy. Especially in the development of biologicals, which are now successfully used in the treatment of rheumatoid arthritis, the selection of the right animal model is pivotal. Non-human primates could help to bridge the evolutionary gap between rodent models and human patients.

Endogenous TLR ligands and autoimmunity

Based on an evolutionary conserved repertoire Toll-like-receptors (TLRs) donate specificity to innate immune cells. Therefore, TLRs are considered as paradigmatic for "self" versus "non-self" discrimination. This view, however, needs to be modified since TLR's also appear to recognise "endogeneous", that is host-derived ligands, examples being host-derived DNA and -RNA. Here I discuss physiological and pathophysiological consequences of endogeneous ligand-recognition by TLRs. I conclude that endogeneous ligand recognition by TLRs drives sterile inflammation sustained by innate immune cells in certain autoimmune disorders.

Effects of the major histocompatibility complex loci and T-cell receptor beta-chain repertoire on Theiler's virus-induced demyelinating disease

We have investigated the potential effects of H-2 and T-cell receptor (TCR) V beta family genes on induction of T-cell immunity and susceptibility to virally induced demyelinating disease by using BALB.S (H-2K(s)A(s)D(s)) and BALB.S 3 R (H-2K(s)A(s)D(d)/L(d)) mice. These parameters were compared with those of highly susceptible SJL/J (H-2K(s)A(s)D(s)) mice that contain only one-half of TCR V beta family genes compared with the above-mentioned strains. Our results demonstrate that BALB.S but not BALB.S 3 R mice are susceptible similar to SJL/J mice. Although the level of CD4(+) T-cell infiltration to the CNS was elevated in susceptible mice, virus-specific immune responses restricted with H-2(s) were similar in these mice. No preferential use of V beta families associated with differences in the major histocompatibility complex (MHC) components was apparent. However, the pattern and sequence of CDR 3 distribution shows T-cell clonal accumulation in the CNS associated with the H-2 components. Further anti-CD8 antibody treatment of resistant BALB.S 3 R mice abrogated resistance to demyelinating disease, indicating that CD8(+) T cells restricted with H-2D(d)/L(d) are most likely to exert resistance in BALB.S 3 R mice. These studies indicated that TCR V beta and MHC class II genes are the secondary to a particular MHC class I gene expression in susceptibility to virally induced demyelinating disease.

Fine mapping of the multiple sclerosis susceptibility locus on 5p14-p12

Linkage analyses have identified four major MS susceptibility loci in Finns. Here we have fine mapped the region on chromosome 5p in 28 Finnish MS families. Marker D5S416 provided the highest pairwise LOD score, and multipoint and haplotype analyses restrict the critical region to about 5.3 Mb on 5p15 between markers D5S1987 and D5S416. Ascertaining for HLA type and geographical origin indicated that families with and without the HLA DR15 risk haplotype, as well as families within and outside an internal high-risk region, contributed to the linkage to 5p, implying the general significance for this locus in Finnish MS families.

Modeling human arthritic diseases in nonhuman primates

Models of rheumatoid arthritis (RA) in laboratory animals are important tools for research into pathogenic mechanisms and the development of effective, safe therapies. Rodent models (rats and mice) have provided important information about the pathogenic mechanisms. However, the evolutionary distance between rodents and humans hampers the translation of scientific principles into effective therapies. The impact of the genetic distance between the species is especially seen with treatments based on biological molecules, which are usually species-specific. The outbred nature and the closer anatomical, genetic, microbiological, physiological, and immunological similarity of nonhuman primates to humans may help to bridge the wide gap between inbred rodent strain models and the heterogeneous RA patient population. Here we review clinical, immunological and pathological aspects of the rhesus monkey model of collagen-induced arthritis, which has emerged as a reproducible model of human RA in nonhuman primates.

Identification of epistasis through a partial advanced intercross reveals three arthritis loci within the Cia5 QTL in mice

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.

Genetically Dominant Spinal Cord Repair in a Murine Model of Chronic Progressive Multiple Sclerosis

For reasons that are not well understood, central nervous system repair in multiple sclerosis is often minimal. We present evidence, in a murine model of chronic progressive multiple sclerosis, that genetic factors can substantially influence remyelination, axonal integrity, and neurologic function. Four inbred mouse strains, SJL, B10.D1-H2(q), FVB, and SWR, developed extensive inflammatory demyelination by 3 months after infection with Theiler's murine encephalomyelitis virus. Demyelination continued lifelong in SJL and B10.D1-H2(q) mice, accompanied by axonal injury, minimal remyelination, and progressive motor dysfunction. In contrast, FVB and SWR mice showed less axonal injury, progressive remyelination, and stabilization of motor function. Genetic dominance of the reparative traits was demonstrated by crossing remyelinating strains (FVB and SWR) with nonremyelinating strains (SJL and B10.D1-H2(q)). All F1 mice developed a phenotype identical to FVB and SWR, showing extensive remyelination, partial preservation of axons, and preserved motor function. Analyses of viral RNA and antigen, immune cell infiltration, and antiviral antibody titers did not predict the phenotypic differences between strains. These results highlight the significant extent to which hereditary factors can control disease course and demonstrate that the switch from a pathogenic to a reparative phenotype can occur even after prolonged inflammatory demyelination.

Dissection of the genetic complexity of arthritis using animal models

The exploding progress in genomic technology and knowledge now opens the possibility to actually identify the molecular mechanisms in disease. However, inflammatory diseases such as rheumatoid arthritis (RA) and multiple sclerosis (MS), are complex and polygenic and remain a challenge. One possible shortcut could be the use of inbred animals as models for RA and MS for the genetic analysis. These models have been extensively characterized and show a similar degree of complexity as the corresponding human diseases. Using these models linkage analysis followed by isolation of the loci in congenic strains have been shown to be highly efficient and have provided fundamental new knowledge on the genetic control of these diseases. The genetically controlled congenic strains are also useful as scientific tools. They can be used for the identification of the disease-associated genes and, thereby, the essential disease pathways that have been selected by nature. We know that this is possible since we have succeeded in identifying the genes within two of the congenic regions; the MHC class II gene Aq controlling immune response and the Ncf1 gene controlling oxidative burst. Both of these genes are associated with T cell activation and arthritis severity.

Genetic heterogeneity of autoimmune disorders in the nonobese diabetic mouse

The nonobese diabetic mouse is highly susceptible not only to diabetes but to several autoimmune diseases, and one might suspect that these are controlled by a shared set of genes. However, based on various gene-segregation experiments, it seems that only a few loci are shared and that each disorder is influenced also by a unique set of genes.

New loci regulating rat myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis

Myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis (EAE) is an inflammatory disease in rats that closely mimics many clinical and histopathological aspects of multiple sclerosis. Non-MHC quantitative trait loci regulating myelin oligodendrocyte glycoprotein-induced EAE have previously been identified in the EAE-permissive strain, DA, on rat chromosomes 4, 10, 15, and 18. To find any additional gene loci in another well-known EAE-permissive strain and thereby to assess any genetic heterogeneity in the regulation of the disease, we have performed a genome-wide linkage analysis in a reciprocal (LEW.1AV1 x PVG.1AV1) male/female F(2) population (n = 185). We examined reciprocal crosses, but no parent-of-origin effect was detected. The parental rat strains share the RT1(av1) MHC haplotype; thus, non-MHC genes control differences in EAE susceptibility. We identified Eae16 on chromosome 8 and Eae17 on chromosome 13, significantly linked to EAE phenotypes. Two loci, on chromosomes 1 and 17, respectively showed suggestive linkage to clinical and histopathological EAE phenotypes. Eae16 and Eae17 differ from those found in previously studied strain combinations, thus demonstrating genetic heterogeneity of EAE. Furthermore, we detected a locus-specific parent-of-origin effect with suggestive linkage in Eae17. Further genetic and functional dissection of these loci may disclose critical disease-regulating molecular mechanisms.

Disruption of the C5a receptor gene fails to protect against experimental allergic encephalomyelitis

Activation of the complement system generates the anaphylatoxic peptide C5a, which elicits a broad range of inflammatory activities. The biological activities of C5a are mediated through its binding to the widely expressed C5a receptor (C5aR), a G-protein-coupled seven transmembrane domain receptor. In experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis, the C5aR is expressed on monocytes/macrophages, reactive astrocytes and T cells infiltrating the central nervous system (CNS). To investigate the role of the C5aR in this T cell-driven autoimmune model, we induced EAE in C5aR-deficient mice (C5aR(-/-)) and wild-type mice using a myelin oligodendrocyte glycoprotein (MOG) peptide as the immunogen. We found that C5aR(-/-) mice were fully susceptible to MOG-induced EAE with no difference in disease onset or severity in C5aR(-/-) mice compared to control mice. Cellular infiltrates (macrophages and T cells) were similar in the spinal cords of both animal groups and splenic T cells from C5aR(-/-) mice and control mice responded identically to MOG in T cell proliferation assays. Ribonuclease protection assays demonstrated no significant differences in pro-inflammatory gene expression between receptor-deficient and sufficient mice. These results indicate that the C5aR is not an essential mediator in the induction and progression of EAE.

Autoantibody patterns in diabetes-prone NOD mice and in standard C57BL/6 mice

Autoantibodies are commonly found in healthy individuals and strains of mice that are not prone to autoimmunity. The present study was undertaken to identify self antigens recognized by serum autoantibodies from unimmunized mice of two strains: NOD mice prone to spontaneously develop autoimmune diabetes and C57BL/6 mice known to be relatively resistant to autoimmune disease. IgM and IgG autoantibodies detected in the sera of NOD and C57BL/6 mice manifested different patterns of reactivity. The IgM autoantibodies from C57BL/6 serum reacted with more self antigens and showed higher OD values than the IgM autoantibodies from NOD mice. In contrast, the IgG autoantibodies from NOD serum reacted with more antigens and displayed higher OD readings than did IgG autoantibodies from C57BL/6 mice. Among the antigens recognized by the autoantibodies, particularly of the IgG class, were self antigens known to induce experimental autoimmune diseases in NOD and C57BL/6 mice. In addition, IgG autoantibodies from NOD mice reacted with self antigens reported to mark the spontaneous autoimmune diabetes that characterizes this strain of mice. These results suggest that naturally occurring IgG autoantibodies reflect susceptibility to induction of specific autoimmune diseases. In addition, the results suggest that IgM autoantibodies may by associated with mechanisms that might prevent autoimmune disease.

IL-10-deficient B10.Q mice develop more severe collagen-induced arthritis, but are protected from arthritis induced with anti-type II collagen antibodies

IL-10 is a pleiotropic cytokine with stimulatory and inhibitory properties, and is thought to have a protective role in rheumatoid arthritis and collagen-induced arthritis (CIA). In this study, we investigated how IL-10 deficiency affects CIA and anti-collagen type II (CII) Ab-transferred arthritis in C57BL/10.Q (B10.Q) mice. The B10.Q.IL-10(-/-) mice had an 8-cM 129/Ola fragment around the IL-10 gene. The mice were treated with antibiotics, appeared healthy, and had no colitis. T cells from IL-10(-/-) mice expressed similar levels of IFN-gamma, IL-2, and IL-4 after mitogen stimulation; however, macrophages showed a reduced TNF-alpha production compared with IL-10(+/-) littermates. IL-10(-/-) mice had an increased incidence, and a more severe CIA disease than the IL-10(+/-) littermates. To study the role of IL-10 in T cell tolerance, IL-10(-/-) were crossed into mice carrying the immunodominant epitope, CII(256-270), in cartilage (MMC) or in skin (TSC). Both IL-10(-/-) and IL-10(+/-) MMC and TSC mice were completely tolerized against CIA, indicating that lack of IL-10 in this context did not break tolerance. To investigate whether IL-10 was important in the effector phase of CIA, arthritis was induced with anti-CII Abs. Surprisingly, IL-10(-/-) were less susceptible to Ab-transferred arthritis, as only 30% showed signs of disease compared with 90% of the littermates. Therefore, IL-10 seemed to have a protective role in CIA, but seemed to exacerbate the arthritogenicity of anti-CII Abs. These data emphasize the importance of studying IL-10 in a defined genetic context in vivo, to understand its role in a complex disease like arthritis.

The genetics of complex autoimmune diseases: non-MHC susceptibility genes

Susceptibility to complex autoimmune diseases (AIDs) is a multigenic phenotype affected by a variety of genetic and environmental or stochastic factors. After over a decade of linkage analyses, the identification of non-major histocompatibility complex (non-MHC) susceptibility alleles has proved to be difficult, predominantly because of extensive genetic heterogeneity and possible epistatic interactions among the multiple genes required for disease development. Despite these difficulties, progress has been made in elucidating the genetic mechanisms that influence the inheritance of susceptibility, and the pace of gene discovery is accelerating. An intriguing new finding has been the colocalization of several AID susceptibility genes in both rodent models and human linkage studies. This may indicate that several susceptibility alleles affect multiple AIDs, or alternatively that genomic organization has resulted in the clustering of many immune system genes. The completion of the human genome sequence, coupled with the imminent completion of the mouse genome, should yield key information that will dramatically enhance the rate of gene discovery in complex conditions such as AID susceptibility.

Murine lupus genetics: lessons learned

Recent reverse genetic studies in murine lupus have taught us the following lessons: (1) Lupus is extremely polygenic; (2) A single locus may be associated with many different phenotypes; (3) What appears to be a single locus may turn out to be a cluster of loci; (4) Different loci facilitate different immunologic steps leading to lupus; (5) Epistatic interactions between loci may engender novel autoimmune phenotypes; (6) Whereas some loci may be pathogenic, others may confer disease resistance; (7) Whereas the expression of some loci is sex-dependent, the expression of others clearly is not; (8) Two or more loci may have an impact on the same phenotype; (9) Lupus susceptibility loci appear to co-cluster with other autoimmunity susceptibility loci; (10) Lupus genes are likely to be polymorphic alleles with subtle impacts, rather than outright mutations with extreme functions. In contrast, forward genetic studies have revealed that molecules that impact apoptosis, the clearance of apoptotic cells, B-cell or T-cell function, and end-organ pathology can all potentially contribute to lupus. Collectively, the loci and genes identified by these two different approaches factorize into a few distinct pathways leading to lupus. Delineating the molecular mediators of these distinct checkpoints is the challenge that lies ahead.

The T cell regulator gene SH2D2A contributes to the genetic susceptibility of multiple sclerosis

The T cell specific adapter protein (TSAd) encoded by the SH2D2A gene is involved in the control of T cell activation. The gene is located in the 1q21 region, which has been implicated in susceptibility to experimental allergic encephalomyelitis in the mouse. We therefore evaluated whether a polymorphic GA repeat (GA(13)-GA(33)) within the promoter region of the SH2D2A gene shows association to multiple sclerosis (MS). The frequency of the short alleles GA(13-16) was increased among 313 Norwegian MS patients compared to 277 healthy controls (0.332 vs 0.249, OR 1.5, Pc = 0.03). Transmission disequilibrium analysis in 146 Scandinavian families with at least two affected sibs showed increased transmission of GA(16) to MS patients. No linkage or association of MS to four genetic markers flanking the SH2D2A gene was observed. After activation of naive CD4(+) T cells, T cells homozygous for MS associated short alleles displayed lower level of TSAd ex vivo than T cells carrying at least one long allele, which were not associated to MS. Since the SH2D2A protein modulates T cell activation, this may be a mechanism for how short SH2D2A alleles confer susceptibility to develop MS.

Genetic control of collagen-induced arthritis in a cross with NOD and C57BL/10 mice is dependent on gene regions encoding complement factor 5 and FcgammaRIIb and is not associated with loci controlling diabetes

The nonobese diabetic (NOD) mouse spontaneously develops autoimmune-mediated diseases such as diabetes and Sjögren's syndrome. To investigate whether NOD genes also promote autoimmune-mediated arthritis we established a NOD strain with an MHC class II fragment containing the A(q) class II gene predisposing for collagen induced arthritis (NOD.Q). However, this mouse was resistant to arthritis in contrast to other A(q) expressing strains such as B10.Q and DBA/1. To determine the major resistance factor/s, a genetic analysis was performed. (NOD.Q x B10.Q)F1 mice were resistant, whereas 27% of the (NOD.Q x B10.Q)F2 mice developed severe arthritis. Genetic mapping of 353 F2 mice revealed two loci associated with arthritis. One locus was found on chromosome 2 (LOD score 9.8), at the location of the complement factor 5 (C5) gene. The susceptibility allele was from B10.Q, which contains a productive C5 encoding gene in contrast to NOD.Q. The other significant locus was found on chromosome 1 (LOD score 5.6) close to the Fc-gamma receptor IIb gene, where NOD carried the susceptible allele. An interaction between the two loci was observed, indicating that they operate on the same or on interacting pathways. The genetic control of arthritis is unique in comparison to diabetes, since none of these loci have been identified in analysis of diabetes susceptibility.

Complex genetic control in a rat model for rheumatoid arthritis

We have defined previously five quantitative trait loci controlling development of pristane-induced arthritis in a cross between E3 and DA rats. To define new loci controlling the disease we have mapped three recombinant inbred strains between DA and E3 and analysed an F2 cross between DA rats and one of these RI strains. Two novel loci affecting disease severity are identified on chromosome 1 (Pia8) and chromosome 4 (Pia7) respectively. We could also reproduce the earlier identified Pia3 locus on chromosome 6 associated with arthritis onset. In the original E3xDA F2 cross, neither of the loci Pia7, Pia8, or Pia1 showed any association with arthritis. To investigate the possibility of interacting loci preventing the phenotypic expression of other loci, the E3xDA F2 cross was re-analysed with a model for a two locus interaction, knowing the presence of these newly identified loci. We found suggestive evidence for an interaction where an effect of Pia7 and Pia1 on disease severity depends on DA homozygosity at specific loci, which themselves do not confer susceptibility. This shows that additional disease associated loci can be identified if other loci are neutralized. This will be of importance for understanding the complex genetics controlling rheumatoid arthritis.

Amelioration of collagen-induced arthritis in DBA/1J mice by recombinant TSG-6, a tumor necrosis factor/interleukin-1-inducible protein

OBJECTIVE

To examine the effect of recombinant TSG-6 on collagen-induced arthritis (CIA) in DBA/1J mice. TSG-6 is a tumor necrosis factor (TNF)/ interleukin-1 (IL-1)-inducible hyaluronan-binding protein produced by synovial cells and chondrocytes that is present in synovial fluids of patients with rheumatoid arthritis.

METHODS

To determine the effect of TSG-6 on chronic inflammatory joint disease, we induced CIA in DBA/1J mice by immunization with bovine type II collagen. Animals were treated with 12 intraperitoneal doses of 200 microg of recombinant TSG-6, beginning 3 days before the expected onset of disease symptoms. Progression of arthritis was monitored by determining the disease incidence, arthritis index, and footpad swelling. Levels of IgG1, IgG2a, and IgG2b antibodies against bovine and murine type II collagen and serum concentrations of IL-6 were determined at various time points. Histologic examination of affected joints was performed approximately 20 days after the onset of arthritis.

RESULTS

Treatment with recombinant TSG-6 protein had a potent ameliorative effect, manifested by decreases in the disease incidence, arthritis index, and footpad swelling. Histologic examination of affected joints in TSG-6-treated animals revealed little pannus formation and cartilage erosion, features which were conspicuous in control mice. Animals treated with recombinant TSG-6 developed significantly reduced levels of IgG1, IgG2a, and IgG2b antibodies against bovine and murine type II collagen.

CONCLUSION

The antiinflammatory effect of the TNF/IL-1-inducible TSG-6 protein in murine CIA suggests a role for this protein as an endogenous regulator of the inflammatory process.

Genetic and epigenetic influence on EAE phenotypes induced with different encephalitogenic peptides

Different encephalitogenic peptides can induce two distinct experimental autoimmune encephalomyelitis (EAE) phenotypes in different mouse strains. To determine whether different peptides induce distinct phenotypes in genetically identical mice, parental strain and (SJLXC3H/HeJ)F1 mice were sensitized with myelin proteolipid protein peptide p139-151 or p215-232. p139-151 was non-encephalitogenic in C3H/HeJ mice and p215-232 was non-encephalitogenic in SJL mice. p139-151 induced typical acute EAE in SJL and F1 mice with most CNS inflammatory/demyelinating lesions located in the spinal cord. p215-232 induced mild clinical disease in only two of 10 C3H/HeJ mice; in 11 of 13 F1 mice (85%) it induced a disease spectrum that included typical paralytic acute EAE with a predominance of spinal cord lesions and later-onset mild EAE with predominance of brain stem/cerebellar lesions. Thus, the EAE phenotype induced in F1 mice by one encephalitogen, e.g. p139-151, can be the same as that induced in the susceptible parent. However, other encephalitogenic peptides, e.g. p215-232, may induce a broad range of heterogeneous EAE phenotypes in syngeneic mice. These data indicate that in some encephalitogenic responses, epigenetic factors influence EAE incidence, time of onset, severity, neurological signs and CNS lesion distribution.

Rheumatoid arthritis and its animal models: the role of TNF-alpha and the possible absence of specific immune reactions

Rheumatoid arthritis is an organ-specific inflammatory disease of humans. Recent studies have focused on associations with non-MHC genes, new autoantigens and the role of innate immune responses. The success of anti-TNF-alpha in the majority (but, interestingly, not all) of patients has implications for disease mechanisms but the dangers of long-term therapy are becoming clearer. A number of new models of arthritis have been defined and emphasize the importance of the genetic make-up of the host. Attention has also focused on why the joint is a particularly vulnerable site for inflammatory responses.

Mapping autoimmunity genes

Rat and mouse models for the major human autoimmune/inflammatory diseases are under intense genetic scrutiny. Genome-wide linkage studies reveal that each model is regulated by multiple genetic loci. Many of these loci colocalize to homologous genomic regions associated with several different autoimmune diseases of mice, rats and humans. Candidate genes are being identified. Polymorphic alleles associated with these chromosomal segments may represent predisposing genetic elements common to a number of human diseases with very different clinical presentations.

Transgenic mouse models of rheumatoid arthritis

A combined analysis of data available in the literature has demonstrated that the strongest association in rheumatoid arthritis (RA) is with DR genes rather than DQ or DP genes. Functional and structural data of RA-associated DR molecules suggest that selective binding of peptides is the molecular basis for this association. The establishment of functional transgenic mice expressing RA-associated HLA class II molecules has proven to be useful in the delineation of the role of these molecules in immune responses possibly related to RA and in the development of humanized models for this disease. Such humanized mice develop arthritis upon immunization with type II collagen (CII), which shows similarities with RA. Interestingly, the immunodominant T-cell determinant in CII is derived from positions 261-273, which overlap with a previously identified CII T-cell epitope restricted by the mouse Aq molecule, which is associated with collagen-induced arthritis. Studies in collagen transgenic mice have shown that recognition of this peptide may lead either to T-cell tolerance or to an arthritogenic response. It is therefore proposed that the T-cell recognition of the CII peptide bound by DR molecules is one of the molecular interactions of critical importance in the development of RA and accordingly also an important target for prevention and treatment of this disease.