T cell responses to human type II collagen in patients with rheumatoid arthritis and healthy controls

TARM1 contributes to development of arthritis by activating dendritic cells through recognition of collagens

TARM1 is a member of the leukocyte immunoglobulin-like receptor family and stimulates macrophages and neutrophils in vitro by associating with FcRγ. However, the function of this molecule in the regulation of the immune system is unclear. Here, we show that Tarm1 expression is elevated in the joints of rheumatoid arthritis mouse models, and the development of collagen-induced arthritis (CIA) is suppressed in Tarm1-/- mice. T cell priming against type 2 collagen is suppressed in Tarm1-/- mice and antigen-presenting ability of GM-CSF-induced dendritic cells (GM-DCs) from Tarm1-/- mouse bone marrow cells is impaired. We show that type 2 collagen is a functional ligand for TARM1 on GM-DCs and promotes DC maturation. Furthermore, soluble TARM1-Fc and TARM1-Flag inhibit DC maturation and administration of TARM1-Fc blocks the progression of CIA in mice. These results indicate that TARM1 is an important stimulating factor of dendritic cell maturation and could be a good target for the treatment of autoimmune diseases.

Toll-Like Receptor 4-Myeloid Differentiation Primary Response Gene 88 Pathway Is Involved in the Shikonin Treatment of CIA by Regulating Treg/Th17 Expression

OBJECTIVE

To investigate the effect of shikonin on (CIA) collagen-induced arthritis and its influence and mechanism on the balance between Th17 cells and Treg cells.

METHODS

Three doses of shikonin were administered orally to mice before the onset of CIA, and celecoxib was used as positive control drug. The arthritis response was monitored visually by macroscopic scoring and hindpaw swelling. Histology of knee was used to assess the occurrence of cartilage destruction and bone erosion. Serum collagen type II (C II) antibody levels associated with CIA were assessed with ELISAs. RT-PCR and quantitative PCR were employed to determine the mRNA expression of cytokines and TLRs in the surface of DCs in the patella with adjacent synovium and spleen in CIA. The expression of cytokines and transcription factors in the peripheral immune organs was tested by Western blotting.

RESULTS

Shikonin treatment suppressed the macroscopic score and incidence of arthritis. Swelling of hind paws, cartilage destruction, and serum anti-C II concentration were delayed with shikonin when compared to controls. Shikonin treatment suppressed the arthritis in a dose-dependent manner. Moreover, the expression of Th17 cytokines (IL-17A) was greatly inhibited both in the synovium and spleen in treated groups compared with those in control groups. The mRNA and protein levels of IL-10 and TGF-β, however, were upregulated after shikonin treatment. The expression of Foxp3 in the synovium and spleen was upregulated, and the expression of ROR-γt in the synovium and spleen was downregulated after shikonin treatment through RT-PCR, quantitative PCR, and Western blotting. The DCs in the spleen of shikonin-treated mice had lower expression of TLR4 and MyD88, and the expression of TLR2 and TLR9 in the spleen was not different between the two groups.

CONCLUSION

Shikonin has anti-inflammatory effects on CIA. Shikonin treatment can inhibit Th17 cytokines expression and induce Treg responses through inhibiting the activation of TLR4/MyD88 pathway.

Chronic lymphocytic leukemia cells bind and present the erythrocyte protein band 3: possible role as initiators of autoimmune hemolytic anemia

The mechanisms underlying the frequent association between chronic lymphocytic leukemia (CLL) and autoimmune hemolytic anemia are currently unclear. The erythrocyte protein band 3 (B3) is one of the most frequently targeted Ags in autoimmune hemolytic anemia. In this study, we show that CLL cells specifically recognize B3 through a still unidentified receptor. B3 interaction with CLL cells involves the recognition of its N-terminal domain and leads to its internalization. Interestingly, when binding of erythrocyte-derived vesicles as found physiologically in blood was assessed, we observed that CLL cells could only interact with inside-out vesicles, being this interaction strongly dependent on the recognition of the N-terminal portion of B3. We then examined T cell responses to B3 using circulating CLL cells as APCs. Resting B3-pulsed CLL cells were unable to induce T cell proliferation. However, when deficient costimulation was overcome by CD40 engagement, B3-pulsed CLL cells were capable of activating CD4(+) T cells in a HLA-DR-dependent fashion. Therefore, our work shows that CLL cells can specifically bind, capture, and present B3 to T cells when in an activated state, an ability that could allow the neoplastic clone to trigger the autoaggressive process against erythrocytes.

Autoantibodies in rheumatoid arthritis: a review

Emerging insights into the importance of B cells in the pathogenesis of rheumatoid arthritis (RA) as highlighted by the efficacy of B cell depletion is one factor that has contributed to the upsurge of interest in the potential role of autoantibodies both as disease markers and with respect to a pathogenic role. Since the initial description of rheumatoid factor (RF), a large number of both disease-specific and non-specific autoantibodies have been described in patients with RA including antibodies to type II collagen (CII), immunoglobulin binding protein (BiP) and antibodies directed at citrullinated peptides (anti-CCP) and other citrullinated proteins such as vimentin (anti-Sa) . Despite some overlap the serological profile of RA does appear to be distinct from other diseases such as SLE . Although the precise mechanisms responsible for the formation of these antibodies have not been well defined their presence must reflect the interaction between T and B cells believed to be relevant to the pathogenesis of RA. The specificity of the association of such factors as anti-CCP and anti-BiP with RA may reflect unique pathogenic events leading to the processing and presentation of the "cryptic self" . Ease of measurement and stability make autoantibodies attractive diagnostic and prognostic markers particularly in early disease when it may be difficult to distinguish self-limiting synovitis from persistent disease . The purpose of this article is to provide an overview of the current state of knowledge of the spectrum of autoantibodies thus far characterised in individuals with rheumatoid arthritis, and discuss their diagnostic, prognostic and pathogenetic relevance.

Oral administration of type-II collagen peptide 250-270 suppresses specific cellular and humoral immune response in collagen-induced arthritis

Oral antigen is an attractive approach for the treatment of autoimmune and inflammatory diseases. Establishment of immune markers and methods in evaluating the effects of antigen-specific cellular and humoral immune responses will help the application of oral tolerance in the treatment of human diseases. The present article observed the effects of chicken collagen II (CII), the recombinant polymerized human collagen II 250-270 (rhCII 250-270) peptide and synthesized human CII 250-270 (syCII 250-270) peptide on the induction of antigen-specific autoimmune response in rheumatoid arthritis (RA) peripheral blood mononuclear cells (PBMC) and on the specific cellular and humoral immune response in collagen-induced arthritis (CIA) and mice fed with CII (250-270) prior to immunization with CII. In the study, proliferation, activation and intracellular cytokine production of antigen-specific T lymphocytes were simultaneously analyzed by bromodeoxyuridine (BrdU) incorporation and flow cytometry at the single-cell level. The antigen-specific antibody and antibody-forming cells were detected by ELISA and ELISPOT, respectively. CII (250-270) was found to have stimulated the response of specific lymphocytes in PBMC from RA patients, including the increase expression of surface activation antigen marker CD69 and CD25, and DNA synthesis. Mice, fed with CII (250-270) before CII immunization, had significantly lower arthritic scores than the mice immunized with CII alone, and the body weight of the former increased during the study period. Furthermore, the specific T cell activity, proliferation and secretion of interferon (IFN)-gamma in spleen cells were actively suppressed in CII (250-270)-fed mice, and the serum anti-CII, anti-CII (250-270) antibody activities and the frequency of specific antibody-forming spleen cells were significantly lower in CII (250-270)-fed mice than in mice immunized with CII alone. These observations suggest that oral administration of CII (250-270) can suppress the cellular and humoral immune response in collagen-induced arthritis, and the simultaneous analysis of antigen-specific cellular and humoral immune responses at single-cell level will help the understanding of the oral tolerance mechanisms in CIA and the development of innovative therapeutic intervention for RA.

The Role of Autoreactive T-Cells in the Pathogenesis of Idiopathic Thrombocytopenic Purpura

Idiopathic thrombocytopenic purpura (ITP) is an autoimmune disease mediated by antiplatelet autoantibodies. The major target of these autoantibodies is a platelet membrane glycoprotein, GPIIb-IIIa, which is a receptor for fibrinogen and other ligands. We recently identified CD4+ T-cells autoreactive to GPIIb-IIIa in ITP patients. These T-cells are considered pathogenic because they help B-cells produce antibodies that bind to normal platelet surfaces. GPIIb-IIIa-reactive T-cells respond to chemically reduced and tryptic peptides of GPIIb-IIIa but not to native GPIIb-IIIa, indicating that the epitopes they recognize are "cryptic" determinants generated at a subthreshold level by the processing of native GPIIb-IIIa under normal circumstances. Although GPIIb-IIIa-reactive T-cells are also detected in healthy individuals, they are activated in vivo only in ITP patients. Activation of GPIIb-IIIa-specific T-cells and the subsequent production of pathogenic anti-GPIIb-IIIa antibodies can be induced by functional antigen-presenting cells in the spleen that present cryptic GPIIb-IIIa peptides to these T-cells. The pathogenic process of ITP can be explained as a continuous loop in which B-cells produce antiplatelet autoantibodies, splenic macrophages phagocytose antibody-coated platelets and present GPIIb-IIIa-derived cryptic peptides, and GPIIb-IIIa-reactive CD4+ T-cells exert their helper activity. Further studies examining the mechanisms that induce the processing and presentation of cryptic peptides derived from the platelet antigen at disease onset will clarify how the pathogenic autoantibody response in ITP is initiated.

The role and clinical implications of G6PI in experimental models of rheumatoid arthritis

The antigens that trigger the pathogenic immune response in rheumatoid arthritis (RA) remain unknown. Until recently it was assumed that either viral or microbial antigens, or joint-specific antigens were the target of arthritogenic T and B lymphocytes in RA. Consequently, murine models of arthritis are induced by immunization with either joint-specific antigens such as type II collagen or microbial products such as streptococcal cell wall. In the K/B×N T-cell receptor transgenic mouse model arthritis is caused by a systemic autoimmune response to the ubiquitously expressed glycolytic enzyme glucose-6-phosphate isomerase (G6PI). The autoreactive transgenic T cells recognize G6PI and provide help for the production of arthritogenic IgG antibodies against G6PI. More recently it was shown that G6PI immunization induces severe symmetrical peripheral polyarthritis in genetically unaltered DBA/I mice. In that model CD4⁺ T cells are necessary not only for the induction but also for the effector phase of arthritis. Here we review the pathomechanisms that lead from systemic autoreactivity to arthritis in these models, consider the relevance of anti-G6PI immune reactivity for RA, and discuss the insights into the pathogenesis of RA and possibly other autoimmune conditions that can be gained from these models.

Tracking of Proinflammatory Collagen-Specific T Cells in Early and Late Collagen-Induced Arthritis in Humanized Mice

Rheumatoid arthritis is a chronic inflammatory disease associated with certain HLA-DR4 subtypes. The target autoantigen(s) is unknown, but type II collagen (CII) is a candidate, with a single immunodominant DR4-restricted 261-273 T cell epitope (CII(261-273)). In the present study, we have prepared HLA-DR4:CII(261-273) tetramers and analyzed peripheral blood, lymph node, and synovial fluid cells from DR4-transgenic mice with early and late collagen-induced arthritis to draw a fuller picture of the role of CII-reactive Th cells in disease development. Their frequencies increased approximately 20-fold in blood 1-2 wk postimmunization, and even more in acutely arthritic joints. Our data strongly suggest that CII-specific Th cells are necessary, but not sufficient for collagen-induced arthritis. The CII-specific Th cells displayed an activated proinflammatory Th1 phenotype, and their expansion correlated with onset and severity of arthritis and also with anti-CII Ab levels. Surprisingly, shortly after the first clinical signs of arthritis, activated HLA-DR4:CII tetramer(+) cells became undetectable in the synovial fluid and rare in the blood, but persisted in lymph nodes. Consequently, future human studies should focus on patients with early arthritis, and on their synovial cells, to re-evaluate the occurrence and pathogenic importance of CII-specific or other Th cells in rheumatoid arthritis.

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.

Identification of type II collagen peptide 261-273-specific T cell clones in a patient with relapsing polychondritis

OBJECTIVE

To characterize and clone T cells specific for type II collagen (CII) in a patient with relapsing polychondritis (RP) and to establish whether the immunodominant epitope of CII determined in HLA transgenic mice is used in the human autoimmune response to CII.

METHODS

T cell responses to CII were examined in a patient with RP, who was heterozygous for the HLA-DR allele DRB1*0101/DRB1*0401. T cell clones were established from this patient and characterized for peptide specificity, class II restriction, cytokine production, and staining with HLA-DRB1*0401 class II tetramers.

RESULTS

A response to CII and the peptide 255-273 was present in this patient. T cells specific for the CII epitope 261-273 were cloned. Evaluation of these clones demonstrated a response to CII 261-273 in the context of both DR alleles. HLA-DR4 CII tetramer did not demonstrate staining of either CII-specific DRB1*0401-restricted T cell clones or a polyclonal population of CII-reactive T cells from this individual.

CONCLUSION

T cells directed against CII were present in this patient with RP. Also, T cell clones isolated from this individual were found to be specific for the CII peptide 261-273 and were restricted to either the DRB1*0101 or the DRB1*0401 allele. These findings establish that a T cell response directed against CII is present in this patient with RP and that the CII peptide 261-273 plays a role in the human immune response to CII.

Shift toward T helper 1 cytokines by type II collagen-reactive T cells in patients with rheumatoid arthritis

OBJECTIVE

To investigate the impact of type II collagen (CII)-reactive T cells on the Th1/Th2 cytokine balance in patients with rheumatoid arthritis (RA).

METHODS

T cell proliferative responses to bovine CII were examined in synovial fluid mononuclear cells (SFMC) and peripheral blood mononuclear cells (PBMC) by mixed lymphocyte culture. CII-reactive T cell lines were generated from the SFMC and PBMC. Interferon-gamma (IFNgamma), interleukin-12 (IL-12), and IL-4 were measured by enzyme-linked immunosorbent assay in the SF, sera, and culture supernatants of PBMC and SFMC that had been stimulated with CII.

RESULTS

The frequency of CII-reactive T cells was higher in the PBMC from RA patients than in that from osteoarthritis patients and healthy control subjects. In RA patients, CII-reactive T cells were more prevalent in SFMC than in PBMC. The mean level of IFNgamma and the ratio of IFNgamma to IL-4 were significantly higher in the culture supernatants of T cells stimulated with CII; these differences were more prominent in SFMC. Levels of IL-12 in the culture supernatants of SFMC and PBMC stimulated with CII were significantly higher than those in unstimulated supernatants. T cell responsiveness correlated well with the level of type 1 cytokines in culture supernatants from RA T cells stimulated with CII. In the CII-reactive cell lines, the increased production of IFNgamma was consistent with clonal expansion.

CONCLUSION

CII-reactive T cells are more abundant in SFMC than in PBMC and are strongly associated with a shift toward Thl cytokine in the inflamed joints of RA patients. Our results suggest that a skewing toward type 1 cytokines by CII-reactive T cells may play an important role in the chronic inflammatory process of RA.

Immunoglobulin heavy chain variable region gene replacement As a mechanism for receptor revision in rheumatoid arthritis synovial tissue B lymphocytes

Mature B cells can alter their antibody repertoires by several mechanisms, including immunoglobulin heavy chain variable region (V(H)) replacement. This process changes the antigen combining site by replacing a portion of the original V(H)/diversity/heavy chain joining region (V(H)DJ(H)) rearrangement with a corresponding portion of a new V(H) segment. This exchange can involve cryptic heptamer-like sequences embedded in the coding regions of V(H) genes. While studying the B lymphocytes that expand in the synovial tissues of patients with rheumatoid arthritis (RA), clones with V(H)DJ(H) variants that were apparently generated by V(H) replacement were identified with surprising frequency (approximately 8%). Examples of multiple independent V(H) replacement events occurring in distinct progeny clones were also identified. These secondary V(H) rearrangements were documented at both the cDNA and genomic DNA levels and involved several heptamer-like sequences at four distinct locations within V(H) (three sites in framework region 3 and one in complementarity determining region 2). The identification of blunt-ended double-stranded DNA breaks at the embedded heptamers and the demonstration of recombinase activating gene (RAG) expression suggested that these rearrangements could occur in the synovial tissues, presumably in pseudo-germinal centers, and that they could be mediated by RAG in a recognition signal sequence-specific manner. The presence of V(H) mutations in the clones that had undergone replacement indicated that these B cells were immunocompetent and could receive and respond to diversification signals. A relationship between these secondary V(H) gene rearrangements and the autoimmunity characteristic of RA should be considered.

Use of soluble peptide-DR4 tetramers to detect synovial T cells specific for cartilage antigens in patients with rheumatoid arthritis

Considerable evidence indicates that CD4(+) T cells are important in the pathogenesis of rheumatoid arthritis (RA), but the antigens recognized by these T cells in the joints of patients remain unclear. Previous studies have suggested that type II collagen (CII) and human cartilage gp39 (HCgp39) are among the most likely synovial antigens to be involved in T cell stimulation in RA. Furthermore, experiments have defined dominant peptide determinants of these antigens when presented by HLA-DR4, the most important RA-associated HLA type. We used fluorescent, soluble peptide-DR4 complexes (tetramers) to detect synovial CD4(+) T cells reactive with CII and HCgp39 in DR4(+) patients. The CII-DR4 complex bound in a specific manner to CII peptide-reactive T cell hybridomas, but did not stain a detectable fraction of synovial CD4(+) cells. A background percentage of positive cells (<0.2%) was not greater in DR4 (DRB1*0401) patients compared with those without this disease-associated allele. Similar results were obtained with the gp39-DR4 complex for nearly all RA patients. In a small subset of DR4(+) patients, however, the percentage of synovial CD4(+) cells binding this complex was above background and could not be attributed to nonspecific binding. These studies demonstrate the potential for peptide-MHC class II tetramers to be used to track antigen-specific T cells in human autoimmune diseases. Together, the results also suggest that the major oligoclonal CD4(+) T cell expansions present in RA joints are not specific for the dominant CII and HCgp39 determinants.

T cells that are naturally tolerant to cartilage-derived type II collagen are involved in the development of collagen-induced arthritis

The immunodominant T-cell epitope that is involved in collagen-induced arthritis (CIA) is the glycosylated type II collagen (CII) peptide 256-270. In CII transgenic mice, which express the immunodominant CII 256-270 epitope in cartilage, the CII-specific T cells are characterized by a partially tolerant state with low proliferative activity in vitro, but with maintained effector functions, such as IFN-gamma secretion and ability to provide B cell help. These mice were still susceptible to CIA. The response was mainly directed to the glycosylated form of the CII 256-270 peptide, rather than to the nonglycosylated peptide. Tolerance induction was rapid; transferred T cells encountered CII within a few days. CII immunization several weeks after thymectomy of the mice did not change their susceptibility to arthritis or the induction of partial T-cell tolerance, excluding a role for recent thymic emigrants. Thus, partially tolerant CII autoreactive T cells are maintained and are crucial for the development of CIA.

Interferon-gamma production in response to in vitro stimulation with collagen type II in rheumatoid arthritis is associated with HLA-DRB1(*)0401 and HLA-DQ8

INTRODUCTION

Despite much work over past decades, whether antigen-specific immune reactions occur in rheumatoid arthritis (RA) and to what extent such reactions are directed towards joint-specific autoantigens is still questionable. One strong indicator for antigenic involvement in RA is the fact that certain major histocompatibility complex (MHC) class II genotypes [human leucocyte antigen (HLA)-DR4 and HLA-DR1[ predispose for the development of the disease [1]. In the present report, collagen type II (CII) was studied as a putative autoantigen on the basis of both clinical and experimental data that show an increased frequency of antibodies to CII in RA patients [2-4] and that show that CII can induce experimental arthritis [5]. It is evident from the literature that RA peripheral blood mononuclear cells (PBMCs) respond poorly to antigenic stimulation [6-8], and in particular evidence for a partial tolerization to CII has been presented [9]. The strategy of the present work has accordingly been to reinvestigate T-cell reactivity to CII in RA patients, to relate it to the response to commonly used recall antigens and to analyze interferon (IFN)-gamma responses as an alternative to proliferative responses.

AIMS

To study cellular immune reactivity to CII in patients with RA and in healthy control individuals and to correlate this reactivity to HLA class II genotypes and to the presence of antibodies to CII in serum.

METHODS

Forty-five patients who met the 1987 American college of Rheumatology classification criteria for RA [10] and 25 healthy control individuals of similar age and sex were included. Twenty-six of these patients who had low levels of anti-CII in serum were randomly chosen, whereas 19 patients with high anti-CII levels were identified by enzyme-linked immunosorbent assay (ELISA)-screening of 400 RA sera. Heparinized blood was density gradient separated and PBMCs were cultured at 1 x 10(6)/ml in RPMI-10% fetal calf serum with or without antigenic stimulation: native or denatured CII (100 microgram/ml), killed influenza virus (Vaxigrip, Pasteur Merieux, Lyon, France; diluted 1:1000) or purified protein derivative (PPD; 10 microgram/ml). CII was heat-denatured in 56 degrees C for 30 min. Cell supernatants were collected after 7 days and IFN-gamma contents were analyzed using ELISA. HLA-DR and HLA-DQ genotyping was performed utilizing a polymerase chain reaction-based technique with sequence-specific oligonucleotide probe hybridization. Nonparametric statistical analyses were utilized throughout the study.

RESULTS

PBMCs from both RA patients and healthy control individuals responded with IFN-gamma production to the same degree to stimulation with native and denatured CII (Fig. 1a), giving median stimulation indexes with native CII of 4.6 for RA patients and 5.4 for health control individuals, and with denatured CII of 2.9 for RA patients and 2.6 for healthy control individuals. RA patients with elevated levels of anti-CII had a weaker IFN-gamma response to both native and denatured CII that did healthy control individuals (P-).02 and 0.04, respectively). Stimulation with the standard recall antigens PPD and killed influenza virus yielded a median stimulation index with PPD of 10.0 for RA patients and 51.3 for healthy control individuals and with influenza of 12.3 for RA patients and 25.7 for healthy, control individuals. The RA patients displayed markedly lower responsiveness to both PPD and killed influenza virus than did healthy control individuals (Fig. 1b). IFN-gamma responses to all antigens were abrogated when coincubating with antibodies blocking MHC class II. The low response to PPD and killed influenza virus in RA patients relative to that of healthy control individuals reflects a general downregulation of antigen-induced responsiveness of T cells from RA patients [6-8]. That no difference between the RA group and the control group was recorded CII-induced IFN-gamma production therefore indicates that there may be an underlying increased responsiveness to CII in RA patients, which is obscured by the general downregulation of T-cell responsiveness in these patients. In order to address this possibility, we calculated the fraction between individual values for the CII-induced IFN-gamma production and the PPD-induced and killed influenza virus-induced IFN-gamma production and the PPD-induced and killed influenza virus-induced IFN-gamma production, and compared these fractions. A highly significant difference between the RA and health control groups was apparent after stimulation with both native CII and denatured CII when expressing the response as a fraction of that with PPD (Fig. 2a). Similar data were obtained using killed influenza virus-stimulated IFN-gamma values as the denominator (Fig. 2b).When comparing the compensated IFN-gamma response to denatured CII stimulation between RA patients with different HLA genotypes, highly significant differences were evident, with HLA-DRB1*0401 patients having greater CII responsiveness than patients who lacked this genotype (Fig. 3a). HLA-DQ8 positive patients also displayed a high responsiveness to CII as compared with HLA-DQ8 negative RA patients (Fig. 3b). These associations between the relative T-cell reactivity to denatured CII and HLA class II genotypes were not seen in healthy control individuals. Similar results were achieved using influenza as denominator (P = 0.02 for HLA-DRB1*0401 and P = 0.01 for HLA-DQ8).

DISCUSSION

No reports have previously systematically taken the general T-cell hyporesponsiveness in RA into account when investigating specific T-cell responses in this disease. In order to address this issue we used the T-cell responses to PPD and killed influenza virus as reference antigens. This was made on the assumption that exposure to these antigens is similar in age-matched and sex-matched groups of RA patients and healthy control individuals. The concept of a general hyporesponsiveness in RA T cells has been documented in several previous reports, in which both nominal antigens [6,7,8] and mitogens [11,12,13] have been used. The fact that a similar functional downregulation in RA PBMCs was obtained with both PPD and killed influenza virus as reference antigens strengthens the validity of our approach. We identified an association between the IFN-gamma response to CII and HLA-DRB1*0401 and HLA-DQ8 in the RA patient group, which is of obvious interest because both these MHC class II alleles have been associated with high responsiveness to CII in transgenic mice that express these human MHC class II molecules [14,15]. There was no association between high anti-CII levels and shared epitope (HLA-DRB1*0401 or HLA-DRB1*0404).

CONCLUSION

CII, a major autoantigen candidate in RA, can elicit an IFN-gamma response in vitro that is associated with HLA-DRB1*0401 and HLA-DQ8 in RA patients. This study, with a partly new methodological approach to a classical problem in RA, has provided some additional support to the notion that CII may be a target autoantigen of importance for a substantial group of RA patients. Continued efforts to identify mechanisms behind the general hyporesponsiveness to antigens in RA, as well as the mechanisms behind the potential partial anergy to CII, may provide us with better opportunities to study the specificity and pathophysiological relevance of anti-CII reactivity in RA.

Antibodies to type II collagen and HLA disease susceptibility markers in rheumatoid arthritis

OBJECTIVE

To seek associations between antibodies to native and denatured type II collagen (NCII and DCII) and HLA in rheumatoid arthritis (RA).

METHODS

One hundred fourteen patients with clinically well-defined RA were HLA-DR and DQ typed. Those who were DR4 positive were subtyped for DRB1*0401-*0408 alleles by polymerase chain reaction using allele-specific oligonucleotide probes. Antibodies to human NCII and DCII (heat-denatured) were measured by enzyme-linked immunosorbent assay. The frequency of HLA alleles was compared in patients grouped according to the presence and absence of antibodies to NCII and DCII.

RESULTS

Twenty-seven patients (24%) were positive for antibodies to NCII. There was a significant increase in the frequency of HLA-DR7 in anti-NCII-positive patients compared with anti-NCII-negative patients (30% versus 9%; P = 0.019) and a significant decrease in HLA-DR3 (7% versus 28%; P = 0.044). Repeating the analyses after excluding the 16 patients who were DR7 positive revealed a significant increase in the frequency of HLA-DR1 in anti-NCII-positive patients compared with anti-NCII-negative patients (63% versus 27%; P = 0.045). Moreover, antibodies to NCII were associated with the third hypervariability region susceptibility sequence QRRAA that is present in DRB1*0101, *0404, *0405, and *0408 (84% versus 47%; P = 0.0085); 24 of 27 anti-NCII-positive patients were positive for either DR7, DR1, or DRB1*0404 or *0408. Thirty patients (26%) were positive for antibodies to DCII. There was a significant increase in the frequency of HLA-DR3 in anti-DCII-positive patients compared with anti-DCII-negative patients (40% versus 18%; P = 0.028).

CONCLUSION

The genetic associations between HLA-DR alleles and antibodies to CII in RA patients is in keeping with the collagen-induced arthritis model and implicates autoimmunity to CII as a major component in the multifactorial pathogenesis of RA.

Enhanced T cell proliferative response to type II collagen and synthetic peptide CII (255-274) in patients with rheumatoid arthritis

OBJECTIVE

To determine the presence of specific immune recognition of type II collagen (CII) and its immunodominant epitope CII (255-274) in patients with rheumatoid arthritis (RA).

METHODS

T cell proliferative responses to bovine CII and a synthetic peptide encompassing CII (255-274) in peripheral blood mononuclear cells (PBMC) and synovial fluid mononuclear cells (SFMC) from RA patients, and in PBMC from osteoarthritis (OA) patients and healthy controls were assayed by mixed lymphocyte culture.

RESULTS

The stimulation index (SI) and the number of positive (SI > or = 2) T cell responses to CII were higher in RA patients (n = 106) than in OA patients (n = 26) and healthy controls (n = 34). T cell responses to CII (255-274) were also enhanced in RA patients and correlated well with those to CII. In SFMC, positive responses to CII or CII (255-274) were detected in 61.9% of 42 RA patients. T cell responses to CII in SFMC were stronger and more prevalent than peripheral responses. The SI and positive responses to CII were higher in early RA than in late RA. Levels of IgG antibodies to CII in synovial fluid inversely correlated with T cell responses to CII.

CONCLUSION

T cell responses to CII or CII (255-274) were enhanced in RA, especially in early disease. Synthetic peptide CII (255-274), as well as native CII, could be recognized as immunogenic antigens by T cells, particularly in the synovial fluid. These observations suggest that CII-reactive T cells play an important role in the pathogenesis of RA. Peripheral tolerance induction using CII (255-274) might be useful in the treatment of RA.

Ability of T cells from patients with rheumatoid arthritis to respond to immunoglobulin G

The ability of T cells from rheumatoid factor (RF)-positive patients with rheumatoid arthritis (RA) to respond to immunoglobulin G (IgG) was assessed. Peripheral blood mononuclear cells (PBMC) from RA patients and normal individuals were cultured with and without human IgG or Mycobacterium tuberculosis-purified protein derivative (PPD) for 7 days and their proliferative response measured at intervals by their ability to take up tritiated thymidine. PBMC from 14/26 RA patients proliferated in response to IgG (taking a stimulation index of 3 or above as positive). The peak response varied between individuals but usually occurred on day 5, the same day, or 1 day later than the peak response to PPD. By contrast, PBMC from a significantly lower proportion (1/9) of normal individuals and patients with other arthritides (0/6) responded to IgG, although all responded to PPD. PBMC from 9/14 RA patients responded to Fab fragments of IgG but only 3/9 to the Fc fragment. Higher proliferative responses from RA PBMC were elicited by IgG aggregates than the original IgG preparation, but PMBC from 5/5 normal individuals and 5/6 patients with other arthritides failed to respond to the aggregates. The response to IgG was human leucocyte antigen (HLA)-DR restricted and mediated by CD4+ T cells. It is considered that these results advance the hypothesis that IgG-reactive T cells contribute to the initiation or perpetuation of RA.

p205 is a major target of autoreactive T cells in rheumatoid arthritis

OBJECTIVE

The p205 autoantigen and interleukin-2 (IL-2) function synergistically to stimulate T lymphocytes from patients with rheumatoid arthritis (RA), and a p205-derived amino acid sequence is identical to an immunoglobulin sequence located within a domain that is reactive with rheumatoid factors (RF). This study was conducted to analyze in detail the T cell immune response against p205 and to investigate whether immunity to p205 may play a role in T cell-mediated immunopathology in active RA.

METHODS

Cibachron blue, protein A-Sepharose, and gel filtration on Sephacryl were used successively to enrich p205 from synovial fluid (SF). T lymphocytes from RA patients were isolated from the peripheral blood (PB), lymph nodes, and SF, and p205 and peptides derived from known sequences were assessed by T cell proliferation assays in the presence of IL-2.

RESULTS

P205-specific proliferation of T cells was observed in PB as well as in SF. When p205 was isolated from RA SF, proliferation of RA T cells peaked on day 3. With p205 purified from SF from trauma patients, there was a significant shift of the maximum T cell proliferation to day 8. T cells were of CD4 or CD8 phenotype, and B cells did not proliferate to a significant degree. The T cell response to p205 was always higher for SF mononuclear cells (SFMC) compared with PBMC (P < 0.001). In 1 RA patient who underwent repeated leukapheresis, this led to a reproducible decline in p205-specific T cell proliferation to control levels. PB T cells specifically proliferating in response to p205 were detected in 20 of 32 RA patients (63%). Of 26 patients with other inflammatory rheumatic diseases, only 1 showed a minor response to p205, while normal donors did not demonstrate a significant T cell proliferation. A synthetic p205-derived peptide, with an amino acid sequence identical to an immunoglobulin sequence located in the area where RF binds, was reactive with T cells from RA patients.

CONCLUSION

P205 appears to be a major target of autoreactive T cells in RA. P205-specific T cells are primed and more abundant at the site of inflammation. As a T cell target in RA, p205 may well be an antigen involved in the initiation of RF production.

Neutrophilic myeloperoxidase-macrophage interactions perpetuate chronic inflammation associated with experimental arthritis

Rheumatoid arthritis is a systemic disease of unknown etiology. The purpose of this study was to elucidate an unrecognized interaction between neutrophilic myeloperoxidase (MPO) and macrophages (Mphi) which could perpetuate the inflammatory response associated with arthritis. A monoarticular arthritis was induced by intra-articular injection of group A streptococcus cell wall fragments (PG-APS) into the ankle joint of female Lewis rats. After swelling/erythema subsided, joints were reinjected with either recombinant MPO or enzymatically inactive MPO (iMPO). Joint measurements were made daily and arthritis was confirmed by histology. Neither iMPO nor MPO could initiate "clinical" arthritis; however, either form of the enzyme injected after PG-APS induced a dose-dependent increase in erythema and swelling. Mannans, which block the binding of MPO to Mo, ablated clinical symptoms. Also, the presence of tumor necrosis factor alpha was observed only in diseased joints using immunocytochemistry.

Autoreactive T cells to platelet GPIIb-IIIa in immune thrombocytopenic purpura. Role in production of anti-platelet autoantibody

T cell proliferative responses to platelet membrane GPIIb-IIIa were examined in 14 patients with chronic immune thrombocytopenic purpura (ITP), 7 systemic lupus erythematosus (SLE) patients with or without thrombocytopenia, and 10 healthy donors. Although peripheral blood T cells from all subjects failed to respond to the protein complex in its native state, reduced GPIIb-IIIa stimulated T cells from three ITP patients and one SLE patient with thrombocytopenia, and tryptic peptides of GPIIb-IIIa stimulated T cells from nearly all subjects. The specificity of the responses for GPIIb-IIIa was confirmed by activation of GPIIb-IIIa-primed T cells by a recombinant GPIIbalpha fragment in secondary cultures. Characterization of T cell response induced by modified GPIIb-IIIa showed that the response was restricted by HLA-DR, the responding T cells had a CD4(+) phenotype, and the proliferation was accelerated only in ITP patients, suggesting in vivo activation of these T cells. In vitro IgG anti-GPIIb-IIIa synthesis in PBMC cultures was induced by modified GPIIb-IIIa specifically in ITP patients with platelet-associated anti-GPIIb-IIIa antibody. Anti-GPIIb-IIIa antibody produced in supernatants was absorbed by incubation with normal platelets. In summary, CD4(+) and HLA-DR-restricted T cells to GPIIb-IIIa are involved in production of anti-platelet autoantibody in ITP patients and are related to the pathogenic process in chronic ITP.

Perpetuation of inflammation associated with experimental arthritis: the role of macrophage activation by neutrophilic myeloperoxidase

Rheumatoid arthritis (RA) is characterized by an abnormal cellular and cytokine infiltration of inflamed joints. This study addresses a previously unrecognized interaction between neutrophilic-myeloperoxidase (MPO) and macrophages (Mphi) which could explain the perpetuation of inflammation associated with RA. A monoarticular arthritis was induced in female Lewis rats by injection of streptococcal cell wall extracts (PG-APS). After swelling and erythema subsided, joints were re-injected with one of the following: porcine MPO or partially inactivated MPO (iMPO). Injection with either MPO or iMPO induced a 'flare' of experimental RA. Blocking the Mphi-mannose receptor by mannans, ablated exacerbation of disease. These results indicate that MPO or iMPO can play a pivotal role in the perpetuation but not initiation of this RA model.