Immunogenetics of collagen-induced arthritis in rats

The potential utility of (2S,4R)-4-[18F] fluoroglutamine as a novel metabolic imaging marker for inflammation explored by rat models of arthritis and paw edema

Purpose

(2S,4R)-4-[18F]fluoroglutamine ([18F]FGln) is a promising metabolic imaging marker in cancer. Based on the fact that major inflammatory cells are heavily dependent on glutamine metabolism like cancer cells, we explored the potential utility of [18F]FGln as a metabolic imaging marker for inflammation in two rat models: carrageenan-induced paw edema (CIPE) and collagen-induced arthritis (CIA).

Procedures

The CIPE model (n = 4) was generated by injecting 200 μL of 3% carrageenan solution into the left hind paw three hours before the PET. The CIA model (n = 4) was generated by injecting 200 μg of collagen emulsion subcutaneously at the tail base 3-4 weeks before the PET. A qualitative scoring system was used to assess the severity of paw inflammation. After a CT scan, 15.7 ± 4.9 MBq of [18F]FGln was injected via the tail vein, followed by a dynamic micro-PET scan for 90 minutes under anesthesia with isoflurane. The standard uptake value of [18F]FGln was measured by placing a volume of interest in each paw. The non-injected right hind paws of the CIPE model rats served as controls for both models. The paws with CIA were pathologically examined after PET.

Results

In CIPE models, uptake in the injected paw was higher compared to the non-injected paw by 52-83%. In CIA models, uptake in the paws with severe inflammation was higher than the averaged controls by 54-173%, while that with mild and no inflammation was slightly higher (33%) and lower (-7%), respectively. Combined overall, the [18F]FGln uptake in CIA showed a significant positive correlation with inflammation severity (r = 0.88, P = 0.009). The pathological findings confirmed profound inflammation in CIA.

Conclusions

[18F]FGln uptake was increased in both acute and chronic inflammation, and the uptake level was significantly correlated with the severity, suggesting its potential utility as a novel metabolic imaging marker for inflammation.

C-Terminal Region of Caveolin-3 Contains a Stretch of Amino Acid Residues Capable of Diminishing Symptoms of Experimental Autoimmune Encephalomyelitis but Not Rheumatoid Arthritis Modeled in Rats

A short synthetic peptide from the C-terminal part of the caveolin-3 structure was tested for experimental autoimmune encephalomyelitis (EAE) treatment in rats. The structure-function similarity established between the novel synthetic peptide of pCav3 and the well-known immunomodulator immunocortin determined pCav3's ability to reduce EAE symptoms in Dark Agouti (DA) rats injected with pCav3 (500 µg/kg). pCav3 was found to interfere with the proliferation of lymphocytes extracted from the LNs of DA rats primed with homogenate injection, with IC50 = 0.42 μM (2.35 mcg/mL). pCav3 affected EAE in a very similar manner as immunocortin. The high degree of homology between the amino acid sequences of pCav3 and immunocortin corresponded well with the therapeutic activities of both peptides, as demonstrated on EAE. The latter peptide, possessing a homologous structure to pCav3, was also tested on EAE to explore whether there were structural restrictions between these peptides implied by the MHC-involved cell machinery. Consequently, immunocortin was further examined with a different autoimmune disease model, collagen-induced arthritis (CIA), established in Sprague-Dawley rats. CIA was established using an intentionally different genetic platform than EAE. Based on the results, it was concluded that the effectiveness of pCav3 and immunocortin peptides in EAE rat model was almost identical, but differed in the rat model of rheumatoid arthritis; thus, efficacy may be sensitive to the MHC type of animals used to establish the autoimmune disease model.

Animal models to study pathogenesis and treatments of cardiac disorders in rheumatoid arthritis: Advances and challenges for clinical translation

Although cardiac diseases such as acute myocardial infarction, heart failure and arrhythmias are the leading cause of cardiovascular complications in rheumatoid arthritis (RA), their pathogenesis is far from being understood and optimal therapeutic options to treat specifically these disorders in RA are lacking. Preclinical studies on animal models of arthritis can help to decipher the complex link between arthritis and the heart, and to identify critical pathways and novel therapeutic targets. This review presented the available data on cardiac disorders in animal models of RA, as well as the current knowledge on pathophysiology and pharmacology of these disorders. Future directions for translational studies in a cardiorheumatic perspective are proposed.

Pharmacokinetics of metformin in collagen-induced arthritis rats

Due to the elevated presence of cytokines, the expressions of metabolic enzymes and drug transporters are altered in rheumatoid arthritis (RA). Given the high incidence of diabetes in patients with RA, the aim of the present study was to investigate the metformin pharmacokinetics of a single oral dose in rats with collagen-induced arthritis (CIA). Blood and urine samples were collected at different timepoints, and analyzed by ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Tissue samples were also collected to investigate the expression of metabolic enzymes and drug transporters by quantitative reverse transcription-polymerase chain reaction (RT-qPCR) and western blot. The results indicated that the bioavailability of metformin was markedly decreased in the CIA rats. Moreover, metformin was not metabolized by enzymes of rat liver microsomes, suggesting that the decreased bioavailability of metformin was independent of the liver metabolism. In addition, the mRNA, protein expression level and activity of the renal organic cation transporter 2 (OCT2) was markedly increased, suggesting that the enhanced renal clearance of metformin in CIA rats may be due to the up-regulated activity of OCT2. In conclusion, our study suggested that the reduced bioavailability of metformin in CIA rats is possibly related to the up-regulated function of the renal protein OCT2.

Anti-Inflammatory and Antiarrhythmic Effects of Beta Blocker in a Rat Model of Rheumatoid Arthritis

Background

Patients with rheumatoid arthritis are at twice the risk of ventricular arrhythmia and sudden cardiac death as the general population. We hypothesize that β‐blocker treatment of rheumatoid arthritis is antiarrhythmic by producing synergistic anticatecholaminergic and anti‐inflammatory effects.

Methods and Results

Collagen‐induced arthritis (CIA) was induced in Lewis rats by immunization with type II collagen in Freund's incomplete adjuvant. The treatment with propranolol (4 mg/kg) started on the first day of immunization. We evaluated the ventricular vulnerability to ventricular arrhythmia using in vivo programmed stimulation and performed ex vivo optical mapping to measure the electrical remodeling of the heart. The ventricular tissue was further processed for immunohistochemical staining and protein array analysis. The assessment of ventricular vulnerability showed that the number and duration of the induced ventricular arrhythmia episodes were increased in CIA rats, which were improved with propranolol treatment. The sympathovagal index and the plasma level of catecholamines significantly increased in CIA rats, whereas the use of propranolol attenuated sympathetic hyperactivity. In the optical mapping study, electrical remodeling, characterized by prolonged action potential duration, slow conduction velocity, and steepened action‐potential duration restitution, were noted in CIA rats and reversed in the propranolol‐treatment group. The propranolol treatment was associated with decreases in paw thickness, fewer inflammatory cell infiltrations in the heart, reduced levels of cardiac inflammatory cytokines, and less cardiac fibrosis as compared with the CIA group.

Conclusions

CIA increased ventricular arrhythmia vulnerability through sympathetic hyperinnervation and proarrhythmic ventricular electrophysiological remodeling. Treatment with propranolol in CIA rats was both anti‐inflammatory and antiarrhythmic.

Phenotypic characterization of type II collagen-induced arthritis in Wistar rats

The aim of the present study was to determine a more specific, efficient and simple method for the induction of collagen-induced arthritis (CIA) in rats. Different strains of rats were injected at the base of the tail with bovine type II collagen (CII) emulsified in incomplete Freund's adjuvant (IFA). The onset and severity of arthritis were evaluated by clinical assessment. The established CIA model was analyzed using a comprehensive examination of clinical, hematological, histological and radiological parameters. The results demonstrated that Wistar rats were the most susceptible strain to CIA followed by Wistar Furth rats, with Sprague Dawley rats being the least susceptible. Following primary and booster immunization, female Wistar rats developed severe arthritis, with an incidence of >83% and low variability in clinical signs. The development of arthritis was accompanied by a significantly elevated erythrocyte sedimentation rate compared with that in the control rats. The radiographic examination revealed bone matrix resorption, considerable soft tissue swelling, periosteal new bone formation and bone erosion in the arthritic joints of the CIA rats. Histopathologically, the synovial joints of CIA rats were characterized by synovial hyperplasia, pannus formation, marked cellular infiltration, bone and cartilage erosion and narrowing of the joint space. The administration of an intradermal injection of only 200 µg bovine CII emulsified in IFA at the base of the tail therefore leads to the successful development of a CIA rat model. This well-characterized CIA rat model could be specifically used to study the pathophysiology of human rheumatoid arthritis as well as to test and develop anti-arthritic agents for humans.

Changes in microarchitectural characteristics at the tibial epiphysis induced by collagen-induced rheumatoid arthritis over time

Background

Little is known about the time course of changes in the microarchitecture of the tibial epiphysis with rheumatoid arthritis (RA), although such information would be valuable in predicting risk of fracture. Therefore, we used in vivo microcomputed tomography (μ-CT) to assess patterns of microarchitectural alterations in the tibial epiphysis using collagen-induced RA in an animal model.

Methods

Bovine type II collagen was injected intradermally into the tails of rats for induction of RA. The tibial joints were scanned by in vivo μ-CT at 0, 4, and 8 weeks following injection. Microarchitectural parameters were measured to evaluate alteration patterns of bone microarchitecture at the tibial epiphysis.

Results

The microarchitectural alterations in an RA group were significantly different from those in a control group from 0 to 4 weeks and from 4 to 8 weeks following injection (P < 0.05). The distribution of trabecular bone thickness and trabecular bone separation from 0 weeks to 8 weeks differed significantly (P < 0.05).

Conclusion

These results indicate that the patterns of microarchitectural alterations at the tibial epiphysis are strongly affected by collagen-induced progression of RA and entail a severe risk of fracture at the tibial epiphysis. This study represents a valuable first approach to tracking periodic and continuous changes in the microarchitectural characteristics of the tibial epiphysis with collagen-induced RA.

Clinical and histopathological evaluation of MDP/collagen induced arthritis rat model (MCIA) after treatment with Urtica dioica, plantago major and Hypericum perforatum L herbal mixture

This study was done to assess the effects of Urtica dioica, Plantago major and Hypericum perforatum L herbal mixture in the MCIA rat model. In addition, a new pathological and clinical arthritis lesion assessment was developed. Sprague-Dawley (SD) rats were immunized with bovine type II collagen and muramyl dipeptide (MDP). Commercial herbal extracts were administered daily to the rats after the immunization for the course of experiment (90 days). Rats were boosted with a second collagen-MDP emulsion 60 days after the first immunization. Paws were daily evaluated macroscopically for redness, swelling, distortion, or ankylosis of the joints. On the day of sacrifice, rat paws were assessed for histopathologic changes. Herbal mixture administration decreased the clinical lesion manifestation in the MCIA rat model and led to development of similar or slightly more severe histopathological lesions compared to rats that did not receive the treatment. The clinical arthritis signs appeared as early as 13 days after the first MDP/collagen injection and with peak incidence at 20 days post-immunization. Histopathologically, animals showed changes ranging from mild to very severe. Administration of the herbal mixture used in this study had a clinical therapeutic effect on the course of the clinical manifestations in the MCIA model, but the herbal treatment had no such effect on the histopathological lesion development and even led to slightly more severe lesions. Rats in the MCIA model developed prominent clinical and histopathological changes that were comparable to rheumatoid arthritis (RA) lesions in humans.

Collagen-induced arthritis

Collagen-induced arthritis (CIA) is an experimental autoimmune disease that can be elicited in susceptible strains of rodents (rat and mouse) and nonhuman primates by immunization with type II collagen (CII), the major constituent protein of articular cartilage. Because of the important similarities between CIA and rheumatoid arthritis, this experimental model of autoimmune arthritis has been the subject of extensive investigation in several laboratories. Protocols for CIA are described in this unit for both the mouse model and the rat model. In addition, protocols are included for the purification of CII from bovine articular joints and chicken sternums, for the purification of collagen a1(II) chains, and for the purification of fragments of these chains following cyanogen bromide (CNBr) digestion. The preparation of CII is a time-consuming procedure but is usually required because of the scarcity and expense of commercial sources of purified native CII. In addition, support protocols are provided for assessing the severity of inflammation following CIA and for measuring B and T cell responses to CII.

Animal models of rheumatoid arthritis and their relevance to human disease

Rodent models of rheumatoid arthritis (RA) are useful tools to study the pathogenic process of RA. Among the most widely used models of RA are the streptococcal cell wall (SCW) arthritis model and the collagen-induced arthritis (CIA). Both innate and adaptive immune mechanisms are involved in these rodent models. While no models perfectly duplicate the condition of human RA, they are easily reproducible, well defined and have proven useful for development of new therapies for arthritis, as exemplified by cytokine blockade therapies. Besides SCW and CIA models, there are numerous others including transgenic models such as K/BxN, induced models such as adjuvant-induced and pristane models, and spontaneous models in certain mouse strains, that have been used to help understand some of the underlying mechanisms. This review provides an update and analysis of RA models in mice and rats. The array of models has provided rheumatologists and immunologists a means to understand the multifactorial disease in humans, to identify new drug targets, and to test new therapies.

Immunotherapy in Collagen-Induced Arthritis: Past, Present, and Future

Type II collagen-induced arthritis has played a critical role in the development of novel approaches to the treatment of rheumatoid arthritis. The model has provided insights into autoimmune mechanisms relevant to the pathogenesis of joint disease and permitted the identification of potential targets for arthritis therapy. Notably, the model excelled in the development of cytokine inhibition for rheumatoid arthritis, with investigations demonstrating that a complex network of cytokine interactions regulate the autoimmune response to collagen. Recent studies of collagen-induced arthritis provide indications of novel approaches to disease intervention. New directions include modulation of the recognition and presentation of autoantigens, inhibition of specific T cell subsets responding to autoantigens, blocking of stimulatory cosignals at the cell surface, decoys for cytoplasmic and nuclear activation signals, interference with lymphocyte migration to the synovial joint, and reduction of the mediators of joint destruction. These approaches can be implemented through gene therapy, biological response mediators, or classic pharmacological intervention.

Neural immune pathways and their connection to inflammatory diseases

Inflammation and inflammatory responses are modulated by a bidirectional communication between the neuroendocrine and immune system. Many lines of research have established the numerous routes by which the immune system and the central nervous system (CNS) communicate. The CNS signals the immune system through hormonal pathways, including the hypothalamic-pituitary-adrenal axis and the hormones of the neuroendocrine stress response, and through neuronal pathways, including the autonomic nervous system. The hypothalamic-pituitary-gonadal axis and sex hormones also have an important immunoregulatory role. The immune system signals the CNS through immune mediators and cytokines that can cross the blood-brain barrier, or signal indirectly through the vagus nerve or second messengers. Neuroendocrine regulation of immune function is essential for survival during stress or infection and to modulate immune responses in inflammatory disease. This review discusses neuroimmune interactions and evidence for the role of such neural immune regulation of inflammation, rather than a discussion of the individual inflammatory mediators, in rheumatoid arthritis.

Localization of Quantitative Trait Loci Regulating Adjuvant-Induced Arthritis in Rats: Evidence for Genetic Factors Common to Multiple Autoimmune Diseases

Adjuvant-induced arthritis (AIA) in rats is a widely used autoimmune experimental model with many features similar to rheumatoid arthritis (RA). To identify potential genetic regulatory mechanisms in RA, we conducted genome-wide linkage analysis in F2 progeny of arthritis-susceptible Dark Agouti (DA) and relatively resistant Fischer 344 (F344) inbred rats. We compared the data with our previously reported investigation of collagen-induced arthritis (CIA), which was expanded in the follow-up study reported in this work. We found two quantitative trait loci (QTLs) in common, i.e., Aia1/Cia1 on chromosome 20, which includes the MHC, and Aia3/Cia3 on chromosome 4. We also identified a second unique QTL in AIA, Aia2, on chromosome 4. Interestingly, the QTL region on chromosome 4 (Aia3/Cia3), like the MHC, appears to be involved in several other autoimmune diseases in rats, including insulin-dependent diabetes, thyroiditis, and experimental autoimmune uveitis. Moreover, an analysis of conserved synteny among rats, mice, and humans suggested that Aia2 and Aia3/Cia3, like Aia1/Cia1, contain candidate genes for several autoimmune/inflammatory diseases in mice and humans, including diabetes, systemic lupus erythematosus, inflammatory bowel disease, asthma/atopy, multiple sclerosis, and RA. The rat models appear to provide a powerful complementary approach to identify and characterize candidate genes that may contribute to autoimmune diseases in several species.

Quantitative trait loci disposing for both experimental arthritis and encephalomyelitis in the DA rat; impact on severity of myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis and antibody isotype pattern

Quantitative trait loci (QTL) controlling inflammatory diseases with different organ specificity may hypothetically either be unique for one disease or shared among different diseases. We have investigated whether five non-MHC QTL controlling susceptibility to experimental arthritis in the DA rat also influence myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE) in an F2 intercross between inbred DA and PVG.RT1a rats. Two of the five chromosome regions affecting arthritis in the DA rat also regulate phenotypes of EAE. The DA allele at markers in Cia3 (collagen-induced arthritis QTL) on chromosome 4 is associated with more severe EAE and high levels of anti-MOG antibodies of the IgG2c subclass. Since production of antibodies of the IgG2c subclass may be stimulated by Th1 cells, and there is previous evidence that such cells promote EAE, it is possible that both of the studied phenotypes are controlled by the same gene or genes regulating Th1/Th2 cell differentiation. Furthermore, we show that Oia2 (oil-induced arthritis QTL) on chromosome 4 regulates levels of anti-MOG antibodies of the IgG1 subclass and of anti-MOG IgE, but that this gene region does not affect clinical disease severity in our study. Since production of IgE and IgG1 may be stimulated by Th2 cells, this QTL may also control Th1/Th2 bias. We conclude that Cia3 and Oia2 regulate MOG-induced EAE in rats. Furthermore, since both EAE and arthritis phenotypes co-localize to these gene regions, they may harbor genes which are key regulators of pathogenic immune responses.

Identification of rat susceptibility loci for adjuvant-oil-induced arthritis

One intradermal injection of incomplete Freund's adjuvant-oil induces a T cell-mediated inflammatory joint disease in DA rats. Susceptibility genes for oil-induced arthritis (OIA) are located both within and outside the major histocompatibility complex (MHC, Oia1). We have searched for disease-linked non-MHC loci in an F2 intercross between DA rats and MHC-identical but arthritis-resistant LEW.1AV1 rats. A genome-wide scan with microsatellite markers revealed two major chromosome regions that control disease incidence and severity: Oia2 on chromosome 4 (P = 4 x 10(-13)) and Oia3 on chromosome 10 (P = 1 x 10(-6)). All animals homozygous for DA alleles at both loci developed severe arthritis, whereas all those homozygous for LEW.1AV1 alleles were resistant. These results have general implications for situations where nonspecific activation of the immune system (e.g., incomplete Freund's adjuvant-oil) causes inflammation and disease, either alone or in conjunction with specific antigens. They may also provide clues to the etiology of inflammatory diseases in humans, including rheumatoid arthritis.

Collagen-induced arthritis in nonhuman primates: multiple epitopes of type II collagen can induce autoimmune-mediated arthritis in outbred cynomolgus monkeys

OBJECTIVE

To define which regions of the type II collagen (CII) molecule result in anticollagen antibody production and the subsequent development of autoantibodies in a collagen-induced arthritis (CIA) nonhuman primate model.

METHODS

Male and female cynomolgus monkeys (2-6 of each sex per group) were immunized with either chicken (Ch), human, or monkey (Mk) CII, or with cyanogen bromide (CB)-generated peptide fragments of ChCII emulsified in Freund's complete adjuvant. Monkeys were observed for the development of arthritis, and sera were collected and analyzed for anticollagen antibody specificity by enzyme-linked immunosorbent assay.

RESULTS

Overt arthritis developed in all groups of monkeys immunized with intact CII and with all major CB peptide fragments of ChCII except CB8. Onset and severity of arthritis correlated best with serum anti-MkCII antibody levels. The levels of IgG autoantibody to MkCII were a result of the cross-reactivity rate of anti-heterologous CII antibodies with MkCII, which was based on the genetic background of individual monkeys rather than on sex differences.

CONCLUSION

CII from several species and disparate regions of the CII molecule were able to induce autoantibody-mediated arthritis in outbred cynomolgus monkeys. The strong anti-MkCII response suggests that epitope spreading or induction of broad-based CII cross-reactivity occurred in these animals. Autoantibody levels to MkCII were higher in CIA-susceptible monkeys than in resistant monkeys, despite comparable antibody levels in response to the various immunizations of CII. These results closely parallel the type of anticollagen responses found in sera from rheumatoid arthritis patients. Perhaps this can be accounted for by similar major histocompatibility complex heterogenicity associated with an outbred population, or maybe this is a primate-specific pattern of reactivity to CII.

Collagen-induced arthritis, an animal model of autoimmunity

Collagen induced arthritis (CIA) is an autoimmune model that in many ways resembles rheumatoid arthritis (RA). Immunization of genetically susceptible strains of rodents and primates with type II collagen (CII) leads to the development of a severe polyarticular arthritis that is mediated by an autoimmune response. Like RA, synovitis and erosions of cartilage and bone are hallmarks of CIA, and susceptibility to both RA and CIA is linked to the expression of specific MHC class II molecules. Although not identical to RA, CIA clearly establishes the biological plausibility that an autoimmune reaction to a cartilage component can lead to a chronic, destructive, polyarthritis. Although it is induced in susceptible animals by immunization with heterologous CII, it is the autoreactive component of the immune response that leads to disease. A wealth of evidence indicates that synovitis is initiated by the production of pathogenic autoreactive antibodies capable of fixing and activating complement. The elucidation of the specific amino acid sequences of collagen that are recognized by the MHC molecules has enabled at least two approaches to specific immunotherapy to be considered. Firstly, small synthetic peptides representing dominant epitopes have been used as effectively as the original antigen as a tolerogen. The rather fastidious physicochemical properties of collagen that make it difficult for its routine use in therapy are thereby circumvented by the use of oligopeptides. Secondly, analysis of the specific amino acid side chains that are involved in MHC contact and TCR recognition enables analog peptides to be devised which can specifically and exquisitely inhibit the response to CII, preventing the onset of arthritis. Further investigations involving this model may contribute to the development of specific immunotherapies in the human disorder.

A genome scan localizes five non-MHC loci controlling collagen-induced arthritis in rats

Identification of specific genetic loci that contribute to susceptibility to rheumatoid arthritis (RA) in humans has been hampered by several factors, including: i) multiple interacting genetic loci contributing to susceptibility; ii) complex interactions of environmental and genetic factors; iii) genetic heterogeneity; and iv) low penetrance. We have, therefore, mapped quantitative trait loci (QTLs) that control inflammatory arthritis susceptibility and/or severity in progeny of two inbred rat strains with significantly different susceptibilities to collagen-induced arthritis (CIA), an animal model for RA. Not surprisingly, we identified a major susceptibility factor, Cia1, on chromosome 20 in the vicinity of the rat major histocompatibility complex (MHC). However, by limiting the analysis to animals with arthritis-susceptible MHC genotypes and using genome-wide QTL analytic techniques, we also found four non-MHC QTLs-Cia2, 3, 4 and 5-on chromosomes 1, 4, 7 and 10, that contributed to disease severity. In addition, a QTL on chromosome 8 was suggestive for linkage. Characterization of the genes underlying these QTLs will facilitate the identification of key biochemical pathways regulating experimental autoimmune arthritis in rats and may provide insights into RA and other human autoimmune diseases. These genes may also represent novel targets for therapy.

Protracted, relapsing and demyelinating experimental autoimmune encephalomyelitis in DA rats immunized with syngeneic spinal cord and incomplete Freund's adjuvant

Experimental autoimmune encephalomyelitis (EAE) is a model for multiple sclerosis (MS). However, MS is a chronic, relapsing and demyelinating disease, whereas EAE in rats is typically a brief and monophasic disorder showing little demyelination. We demonstrate here that DA rats develop severe, protracted and relapsing EAE (SPR-EAE) after a subcutaneous immunization at the tail base with syngeneic spinal cord and incomplete Freund's adjuvant (IFA). The neurological deficits were accompanied by demyelinating inflammatory lesions in the spinal cord, with infiltrating T lymphocytes and perivascular deposition of immunoglobulins and complement. The induction of SPR-EAE was associated with humoral autoreactivity to myelin oligodendrocyte glycoprotein (MOG) and cellular autoreactivity to the rat myelin basic protein (MBP) peptides 69-87 and 87-101. These two peptides, as well as whole rat MBP, were encephalitogenic. In conclusion, we believe that the presently described demyelinating SPR-EAE represents a useful model for MS.

Specific and long-lasting protection from collagen-induced arthritis and oil-induced arthritis in DA rats by administration of immunogens

DA rats develop transient arthritis after subcutaneous immunization with adjuvant-oil, while chronic arthritis and collagen autoreactivity ensues when collagen is added to the oil. We show here that DA rats can be protected from oil-induced arthritis (OIA) and rat collagen-induced arthritis (rCIA) by addition of antigen to these arthritogenic inocula. We have investigated this remarkable phenomenon and demonstrate that both foreign and self antigens can be protective, apparently provided they are immunogenic; hence HSP-65kDa, ovalbumin, rat myelin basic protein, rat IgG and bovine albumin are effective while rat albumin is not. This protection is long-lasting and disease-specific because rats protected from rCIA resist a later attempt to induce arthritis, but not experimental autoimmune encephalomyelitis (EAE). Protection from rCIA depends neither on the blocking of humoral autoreactivity to collagen nor on a change in the isotype profile of anti-collagen antibodies. We demonstrate that immunogens can also be protective when injected intraperitoneally only a few days before onset of arthritis. Our results indicate that protection is mediated through bystander immune reactions towards the co-immunized antigen and that the arthritogenicity of a given provocation, be it adjuvants, microbes or autoantigens, may be a complex net result of arthritogenic and contra-arthritogenic immune reactions.

Type XI and II collagen-induced arthritis in rats: characterization of inbred strains of rats for arthritis-susceptibility and immune-responsiveness to type XI and II collagen

To determine the relationship between susceptibility to bovine type XI and II (BXI and BII) collagen-induced arthritis, we immunized 14 inbred and one outbred strains of rats with BXI and BII. Susceptibility to BXI-arthritis corresponded largely with susceptibility, or resistance, to BII-arthritis. LEW, BB, WF, DA, and WKY were readily susceptible to BXI- and BII-arthritis. Likewise, BII-resistant F344 and BN rats were BXI-resistant. Some strains responded differently to BXI and BII. BUF and COP, which are moderately susceptible to BII, were BXI-resistant, whereas the BII-resistant rats, DA.1N and WF.1N, were partially susceptible to BXI. (F344 x BN) F1 hybrids responded to both collagens suggesting gene complementation. Arthritis occurred in all strains producing the highest titer antisera (LEW, WF and BB). Antibody responses to BXI and BII were generally commensurate within individual strains. DA were susceptible to arthritis but produced low levels of antibody comparable to BN rats which were arthritis-resistant. BXI and BII-susceptibility was variable in rats producing intermediate antibody responses. Antibodies to RXI were detected in all BXI-immunized rats, whereas antibodies to RV and RII were uniformly weaker. DTH to RXI and RII was strong in both groups of rats, correlating poorly with arthritis and antibody responses. These studies show that phenotypic susceptibility to BXI- and BII-arthritis are largely concordant among inbred rat strains but clear differences exist in certain strains; multiple genes are likely involved.

Exacerbation of collagen-induced arthritis in rats by rat cytomegalovirus is antigen-specific

Collagen-Induced Arthritis (CIA) is an experimentally induced and genetically controlled animal model of chronic joint inflammation. In rats, there are informative strain differences in susceptibility to CIA. DA rats (RT1avl) develop severe CIA after immunization with bovine (BII), chick (CII), or homologous rat (RII) type II collagens. In contrast, the MHC-congenic DA. 1N(BN) and WF.1N(BN) rats (RT1n) are relatively resistant to CIA and develop moderate CIA in response to immunization with CII but not BII or RII. We previously found that simultaneous infection with rat cytomegalovirus (RCMV) greatly exacerbates the severity of arthritis that develops in BII-immunized DA rats. To examine the mechanism of RCMV amplification of CIA, the effect of simultaneous infection with RCMV on arthritis and autoimmunity to type II collagen was determined in WF.1N and DA.1N rats after immunization with BII, CII and RII. RCMV increased the incidence of CIA and the level of autoimmunity to type II collagen (skin-testing and IgG antibody titer) selectively in DA.1N and WF.1N rats immunized with CII, but not in littermates immunized with BII, although the transient reversal of CD4+/CD8+ mononuclear cell ratios in peripheral blood that is associated with RCMV infection occurred equally in both BII- and CII- immunized DA.1N rats. Likewise, RCMV infection moderately increased the levels of anti-RII autoimmunity and arthritis in DA rats sub-optimally immunized with RII but had no consistent effect on either anti-RII immunity or arthritis in RII-immunized DA.1N and WF.1n rats. The data show that RCMV augments arthritis only in rats that are genetically susceptible to CIA and that are appropriately immunized with a species of type II collagen that is arthritogenic for the MHC-haplotype being tested. Two possible mechanisms are suggested by these data: RCMV-associated increases in anti-RII autoimmunity in rats with CIA may result from amino acid sequence homologies between RCMV and type II collagen; alternatively, virus-induced pro-inflammatory cytokines may activate RII-reactive lymphocytes thereby potentiating autoimmunity and arthritis.

Susceptibility to relapsing polychondritis is associated with HLA-DR4

OBJECTIVE

To determine the frequency of HLA class II antigens in Caucasian central European patients with relapsing polychondritis (RP).

METHODS

HLA class I, DR, and DQ specificities were identified in 41 patients with RP, and the frequencies were compared with those in 204 healthy, unrelated control subjects. HLA typing was performed using the standard complement-dependent microcytotoxicity assay. HLA-DR genotyping of 12 DR4-positive RP patients and 57 controls was performed by allele-specific oligonucleotide probing after amplification of genomic DNA by polymerase chain reaction.

RESULTS

A significant increase in DR4 antigen frequency was found in the patients (56.1%) as compared with that in healthy controls (25.5%) (Pcorr < 0.001). Genotyping of DR4-positive patients and controls revealed no predominance of any DR4 subtype.

CONCLUSION

There are important clinical similarities and overlaps between RP and rheumatoid arthritis (RA). In RA, the association with DR4 has been well established. Our findings show that although there is a DR4 association with RP, the situation is sufficiently distinct from that of RA to imply considerable differences in pathogenesis of the two conditions.

Association of pepsin with type II collagen (CII) breaks control of CII autoimmunity and triggers development of arthritis in rats

Lewis rats develop arthritis after immunization with heterologous but not homologous rat type II collagen (CII). We have observed that if the rat CII is prepared by pepsin digestion without subsequent extensive purification, it is arthritogenic in Lewis rats. To address whether pepsin in the CII preparations contributed to the development of arthritis and whether this was associated with the induction of an immune response to CII, Lewis rats were immunized with rat CII of various degrees of purity and with various pepsin contents. After immunization with a crude preparation of CII, containing relatively large amounts of pepsin, Lewis rats developed arthritis with an incidence of 80% together with a strong anti-CII autoantibody production. Further purification of the CII on DEAE-Sepharose, which removes pepsin, eliminated the arthritogenic properties and the capacity to activate CII-specific B cells. Likewise, lathyritic CII, prepared without pepsin, induced neither a CII-specific immune response nor arthritis. If, however, pepsin was added to non-arthritogenic batches of rat CII, arthritis appeared at an incidence of 40%. By using an ELISPOT technique to detect antigen-specific interferon-gamma-producing T cells and antibody-producing B cells, the immune response to CII and pepsin can be evaluated. Eleven days after immunization with lathyritic CII and pepsin, a B-cell response towards both CII and pepsin was seen. Pepsin-specific T cells were also seen at day 11, but CII-specific T cells did not appear until day 14 after immunization. In addition, a weak CII-specific proliferative response of the T cells could be demonstrated at day 14 but not at day 11 or 12. These data show that pepsin plays an important role in the triggering of a CII-specific immune response. We suggest a carrier-hapten mechanism where pepsin acts as a carrier and CII as a 'hapten' which will activate CII-specific B cells. Subsequently these CII-specific B cells will break the T-cell tolerance and evoke a T-cell-mediated immune response towards CII.

Vaccination and genetic experiments demonstrate that adjuvant-oil-induced arthritis and homologous type II collagen-induced arthritis in the same rat strain are different diseases

The DA rat is highly susceptible to induction of arthritis after immunization with homologous type II collagen (CII) emulsified in Freund's incomplete adjuvant (FIA), resulting in collagen-induced arthritis (CIA). The DA rat also develops arthritis after injection of FIA alone (oil-induced arthritis (OIA)). This finding allows a direct comparison of two different models for rheumatoid arthritis; one induced with a defined auto-immunogen and one with a pure adjuvant. Both CIA and OIA develop approximately 2 weeks after induction but OIA is a self-limited acute disease whereas CIA induced with homologous CII follows a chronic disease course. Immunization with CII leads to a strong autoantibody response to CII while injection of FIA leads to no or very limited anti-CII antibody response. The Lewis rat develops neither CIA nor OIA while F1 (DA x Lewis) rats develop CIA but not OIA. Olive oil or CII emulsified in olive oil does not induce arthritis in DA rats. Pretreatment with CII in olive oil vaccinates against CIA but not OIA whereas pretreatment with FIA vaccinates against OIA but not CIA. These findings demonstrate that inclusion of CII in the adjuvant leads to a disease distinct from OIA which is characterized by a CII autoimmune response and chronicity of the disease course.

Genetic control of the immune response to collagen by the major histocompatibility complex in the rat: I. Humoral responses to bovine and chick type II collagen

A number of congenic and recombinant rat strains with different RT1 haplotypes on a PVG/c background were immunised with native bovine or chick type II collagen. Only strains with the "u" haplotype were good responders to bovine type II collagen whilst all strains responded to chick type II collagen. However, the "u" haplotype was again associated with the production of the highest amounts of antibody. All the strains responded to a non-collagenous antigen, keyhole limpet haemocyanin, showing that this effect was not a general one relating to all antigens. When antibodies were produced to the immunising collagen, binding of antibodies to native rat type II collagen was also seen. This association, of high amounts of antibody with the "u" haplotype, was inherited in a dominant fashion when F1 and F2 hybrids between low responder (RT1a) and high responder (RT1u) were examined. The recombinant r1 (class I av1, class II c) and r8 (class I av1 and class II u) strains showed that "u" haplotype at class II rather than at class I was associated with the strong response to type II collagen. The absence of arthritis in the "u" haplotype rats, suggests that the "u" haplotype alone is insufficient for arthritis induction after immunisation with type II collagen. It suggests that background genes outside the RT1 complex influence arthritis production as Wistar rats with the RT1u haplotype (but different minor genes outside RT1 complex) give an arthritis incidence of 50% under identical immunisation protocols.

Homologous collagen-induced arthritis in rats and mice are associated with structurally different major histocompatibility complex DQ-like molecules

Collagen-induced arthritis (CIA) in rats, induced with homologous type II collagen (CII), is a genetically more restricted disease and has better resemblance to rheumatoid arthritis by its chronic disease course, than CIA induced with heterologous CII. The DA strain is highly susceptible to CIA induced with homologous CII, while the Lewis strain is resistant. (DAxLew)F1 is susceptible and backcrossing to Lewis reveals a close, but not complete, association of both arthritis and CII responsiveness to the RT1a haplotype. Analyses of congenic strains on DA and Lewis backgrounds suggest that expression of a major histocompatibility complex class II Ba molecule, encoded from the RT1Ba locus, is associated with arthritis susceptibility and CII responsiveness. The second exons coding for the first domains of the alpha and beta chains of both the RT1a and RT1l haplotypes were sequenced and the deduced amino acid sequences compared with the corresponding molecule associated with susceptibility to CIA in the mouse (H-2 Aq). The sequences of the respective alleles revealed no obvious structural homology explaining the extensive similarities in the development of chronic autoimmune arthritis. Instead, this finding implies that different trimolecular constituents (i.e. class II, T cell receptor, and CII peptides) may yield an antigen presentation event that is able to trigger a similar autoaggressiveness in the two rodent species.

Self-tolerance and autoimmunity

Studies of self-tolerance and autoimmunity have moved rapidly into new arenas. These include the definition of at least two mechanisms for tolerance induction in both T and B cells, the creation of new disease-susceptible strains such as the HLA-B27 transgenic rats, the creation of new disease-resistant strains such as I-E or I-Ak NOD transgenic mice, and the precise definition of both antigen and antigen receptor for pathogenic lymphocytes in some models. More effective therapies for autoimmune disease should result from the knowledge gained.