Self-reactive T cells induce and perpetuate chronic relapsing arthritis.

BACKGROUND: CD4+ T cells play a central role during the early stages of rheumatoid arthritis (RA), but to which extent they are required for the perpetuation of the disease is still not fully understood. The aim of the current study was to obtain conclusive evidence that T cells drive chronic relapsing arthritis. METHODS: We used the rat pristane-induced arthritis model, which accurately portrays the chronic relapsing-remitting disease course of RA, to examine the contribution of T cells to chronic arthritis. RESULTS: Rats subjected to whole-body irradiation and injected with CD4+ T cells from lymph nodes of pristane-injected donors developed chronic arthritis that lasted for more than 4 months, whereas T cells from the spleen only induced acute disease. Thymectomy in combination with irradiation enhanced the severity of arthritis, suggesting that sustained lymphopenia promotes T cell-driven chronic inflammation in this model. The ability of T cells to induce chronic arthritis correlated with their expression of Th17-associated transcripts, and while depletion of T cells in rats with chronic PIA led to transient, albeit significant, reduction in disease, neutralization of IL-17 resulted in almost complete and sustained remission. CONCLUSION: These findings show that, once activated, self-reactive T cells can sustain inflammatory responses for extended periods of time and suggest that such responses are promoted in the presence of IL-17.

C57BL/6 mice need MHC class II Aq to develop collagen-induced arthritis dependent on autoreactive T cells.

INTRODUCTION: Collagen-induced arthritis (CIA) has traditionally been performed in MHC class II A(q)-expressing mice, whereas most genetically modified mice are on the C57BL/6 background (expressing the b haplotype of the major histocompatibility complex (MHC) class II region). However, C57BL/6 mice develop arthritis after immunisation with chicken-derived collagen type II (CII), but arthritis susceptibility has been variable, and the immune specificity has not been clarified. OBJECTIVE: To establish a CIA model on the C57BL/6 background with a more predictable and defined immune response to CII. RESULTS: Both chicken and rat CII were arthritogenic in C57BL/6 mice provided they were introduced with high doses of Mycobacterium tuberculosis adjuvant. However, contaminating pepsin was strongly immunogenic and was essential for arthritis development. H-2(b)-restricted T cell epitopes on chicken or rat CII could not be identified, but expression of A(q) on the C57BL/6 background induced T cell response to the CII260-270 epitope, and also prolonged the arthritis to be more chronic. CONCLUSIONS: The putative (auto)antigen and its arthritogenic determinants in C57BL/6 mice remains undisclosed, questioning the value of the model for addressing T cell-driven pathological pathways in arthritis. To circumvent this impediment, we recommend MHC class II congenic C57BL/6N.Q mice, expressing A(q), with which T cell determinants have been thoroughly characterised.

Class II major histocompatibility complex-associated response to type XI collagen regulates the development of chronic arthritis in rats.

OBJECTIVE: Chronic inflammation of the peripheral joints is a hallmark of rheumatoid arthritis (RA). The autoantibody response in RA has been shown to be directed mainly to ubiquitous antigens, whereas the response to cartilage proteins has been less extensively investigated. This study was undertaken to characterize the immune response in pristane-induced arthritis (PIA) in the rat to the cartilage-specific proteins type II collagen (CII) and type XI collagen (CXI) and to genetically fine-map their underlying major histocompatibility complex (MHC) associations. METHODS: The genetic control of CII and CXI immunity was mapped using intra-MHC-recombinant inbred strains immunized with the respective collagens. Reactivity with CII and CXI was tested in acute and chronic PIA and in 356 HLA-typed patients with recently diagnosed RA. RESULTS: Mapping of arthritis susceptibility within the MHC region revealed a 144-223-kb locus containing <12 genes, including paralogs for HLA-DQ and HLA-DR. Susceptibility to CII and CXI was linked to haplotypes RT1(av1) (DA) and RT1(f) (DA.1F), respectively. After injection of pristane, rats of both strains developed weak T cell and IgG responses to CII, but not to CXI. In chronic arthritis, however, collagen reactivity was stronger, specific for CXI, and restricted to rats with RT1(f) MHC. Among RA patients, 12% exhibited a specific IgG response to CXI, 6% to CII, and 6% to both collagens. CONCLUSION: These findings demonstrate a shift in cartilage recognition in early and chronic arthritis in the rat, suggesting that CXI autoreactivity contributes to the perpetuation of chronic disease. The results provide evidence of the importance of joint antigens in arthritis development.

Antibodies to citrullinated proteins: molecular interactions and arthritogenicity.

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.

Cartilage oligomeric matrix protein deficiency promotes early onset and the chronic development of collagen-induced arthritis.

INTRODUCTION: Cartilage oligomeric matrix protein (COMP) is a homopentameric protein in cartilage. The development of arthritis, like collagen-induced arthritis (CIA), involves cartilage as a target tissue. We have investigated the development of CIA in COMP-deficient mice. METHODS: COMP-deficient mice in the 129/Sv background were backcrossed for 10 generations against B10.Q mice, which are susceptible to chronic CIA. COMP-deficient and wild-type mice were tested for onset, incidence, and severity of arthritis in both the collagen and collagen antibody-induced arthritis models. Serum anti-collagen II and anti-COMP antibodies as well as serum COMP levels in arthritic and wild-type mice were measured by enzyme-linked immunosorbent assay. RESULTS: COMP-deficient mice showed a significant early onset and increase in the severity of CIA in the chronic phase, whereas collagen II-antibody titers were similar in COMP-deficient and wild-type controls. COMP antibodies were not found in wild-type mice. Finally, COMP-deficient and wild-type mice responded similarly to collagen antibody-induced arthritis, indicating no difference in how collagen II antibodies interact with COMP-deficient cartilage during the initial stages of arthritis. CONCLUSIONS: COMP deficiency enhances the early onset and development of chronic arthritis but does not affect collagen II autoimmunity. These findings accentuate the importance of COMP in cartilage stability.

Cartilage oligomeric matrix protein induction of chronic arthritis in mice.

OBJECTIVE: To develop a new mouse model for arthritis using cartilage oligomeric matrix protein (COMP) and to study the role of major histocompatibility complex (MHC) and Ncf1 genes in COMP-induced arthritis (COMPIA). METHODS: Native (pentameric) and denatured (monomeric) COMP purified from a rat chondrosarcoma was injected into mice with Freund's adjuvant to induce arthritis. C3H.NB, C3H.Q, B10.P, B10.Q, (B10.Q x DBA/1)F1, (BALB/c x B10.Q)F1, Ncf1 mutated, H-2Aq, H-2Ap, and human DR4+-transgenic mice were used. Anti-COMP antibodies and COMP levels in the immune sera were analyzed, and passive transfer of arthritis with purified immune sera was tested. RESULTS: Immunization with rat COMP induced a severe, chronic, relapsing arthritis, with a female preponderance, in the mice. The disease developed in C3H.NB mice, but not in B10.P mice, although they share the same MHC haplotype. Both H-2q and H-2p MHC haplotypes allowed the initiation of COMPIA. Using H-2Aq-transgenic and H-2Ap-transgenic mice, we demonstrated a role of both the Aq and Ep class II molecules in this model. Interestingly, the introduction of a mutation in the Ncf1 gene, which is responsible for the reduced oxidative burst phenotype, into the COMPIA-resistant B10.Q mouse strain rendered them highly susceptible to arthritis. In addition, the transfer of anti-COMP serum was found to induce arthritis in naive mice. Mice transgenic for the rheumatoid arthritis (RA)-associated DR4 molecule were found to be highly susceptible to COMPIA. CONCLUSION: Using rat COMP, we have developed a new and unique mouse model of chronic arthritis that resembles RA. This model will be useful as an appropriate and alternative model for studying the pathogenesis of RA.

Arthritis induced with minor cartilage proteins.

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.

Type IX collagen deficiency enhances the binding of cartilage-specific antibodies and arthritis severity.

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.

Immunization of rats with homologous type XI collagen leads to chronic and relapsing arthritis with different genetics and joint pathology than arthritis induced with homologous type II collagen.

The most commonly used animal model for rheumatoid arthritis (RA) is collagen-induced arthritis (CIA), induced by immunization with type II collagen (CII), a cartilage restricted protein. In this work we show that type XI collagen (CXI), which is a minor component in cartilage, induces a different form of erosive and chronic relapsing polyarthritis in rats. Using a series of inbred rat strains involving various genetic backgrounds (DA, LEW, E3), and congenic MHC regions (a, u, f, n, c, d), we found that CXI induced arthritis (C(XI)IA) is associated with the RT1f haplotype in contrast to CII induced arthritis (C(II)IA), which is associated with the RT1a and RT1u haplotypes. The C(XI)IA follows a chronic disease course affecting peripheral joints with both progression and relapses, which appear not to cease (occurring >800 days). Susceptible strains showed a sustained antibody response to CXI with time indicating that the autoimmune response was self-perpetuated. Microscopic analysis of the joints at different stages demonstrated the severe destruction of bone and cartilage by pannus tissue consisting of activated macrophages and T cells. The main difference to joints from rats with C(II)IA was larger numbers of infiltrating lymphocytes and these tended to form follicle-like aggregates. Surprisingly, males were more susceptible to C(XI)IA than females whereas the opposite has been observed in other rat arthritis models, including C(II)IA. Taken together, C(XI)IA is a chronic relapsing and erosive polyarthritis that is MHC associated, which in fact fulfills the criteria for diagnosis of RA. Thus the C(XI)IA model will be useful as a novel and relevant animal model for RA.

Predominant selection of T cells specific for the glycosylated collagen type II epitope (263-270) in humanized transgenic mice and in rheumatoid arthritis.

Rheumatoid arthritis (RA) is associated with certain MHC class II alleles and is characterized by a chronic autoimmune response in the joints. Using transgenic mice expressing human DR4 (DRB1*0401) and human CD4, but lacking endogenous MHC class II, we show that posttranslational glycosylation of type II collagen (CII) influences the level of T cell tolerance to this candidate cartilage-specific autoantigen. In such mice, the expression of human CII resulted in a tolerized murine T cell response to human CII. However, tolerance induction remained incomplete, preferentially deleting responses to the nonmodified CII 263-270 epitope, whereas T cell recognition of a glycosylated variant of this epitope was affected to a lesser degree. A similar dominance of T cell responses to CII-glycopeptides was recorded in a cohort of severely affected RA-patients (n = 14). Thus, RA T cells predominantly recognize the immunodominant CII peptide in its glycosylated form and may explain why previously it has been difficult to detect T cell responses to CII in RA patients.