Rheumatoid Arthritis: Nogueira L

Vincent C, Nogueira L, Clavel C, Sebbag M, Serre G. · "Epidermis Differentiation and Rheumatoid Autoimmunity"; UMR 5165 CNRS-Toulouse III University, IFR30 (CNRS-INSERM-Toulouse III University-CHU de Toulouse) Toulouse France. · Autoimmunity. · Pubmed #15804701 No free full text.

Abstract: Anti-perinuclear factor and anti-keratin antibodies have long been known to be specifically associated with rheumatoid arthritis (RA). They were first demonstrated to target various forms of (pro)filaggrin, a protein of stratified epithelia. Then, they were found to belong to a single family of autoantibodies targeting proteins that bear peptidic epitopes centered by a citrullyl residue: the anti-citrullinated protein autoantibodies (ACPA). The main targets of ACPA in the synovial tissue were demonstrated to be citrullinated forms of the a- and beta-chains of fibrin. A chronic conflict between locally produced ACPA and deposits of citrullinated fibrin is probably responsible for self-maintaining of RA synovial inflammation. Various tests for the detection of ACPA have been developed: recent ELISAs confirm their high diagnostic specificity and improve their diagnostic sensitivity. Since ACPA appear very early in the course of the disease, their detection is of major interest to identify RA among recent arthritides. Moreover, their prognostic value may lead to start early 'aggressive' treatments to prevent irreversible joint damage.

Sebbag M, Chapuy-Regaud S, Auger I, Petit-Texeira E, Clavel C, Nogueira L, Vincent C, Cornélis F, Roudier J, Serre G. · Faculté de Médecine, Purpan-IFR30, Unité Différenciation Epidermique et Auto-immunité Rhumatoïde, UMR 5165 CNRS-Toulouse III Université, (CNRS-Inserm-Université Paul Sabatier-CHU de Toulouse), Place du Docteur Baylac, 31059 Toulouse, France. · Joint Bone Spine. · Pubmed #15589429 No free full text.

Abstract: Rheumatoid arthritis (RA) is the most frequent human autoimmune disease, affecting about 1% of the adult population worldwide. A better knowledge of the autoimmune mechanisms involved is essential. We identified the epithelial targets of various autoantibodies specifically associated to RA, as variants of (pro)filaggrin. We also showed that these targets correspond to deiminated ("citrullinated") proteins, of which arginyl residues have been posttranslationally transformed into citrullyl residues by a peptidylarginine deiminase (PAD). Moreover, we and others established that citrullyl residues are indispensable elements of the epitopes recognized by these autoantibodies but only in the context of specific aminoacid sequences. We also demonstrated that these autoantibodies to citrullinated proteins (ACPA) are secreted by plasma cells of the synovial tissue and that their major targets correspond to citrullinated forms of the alpha- and beta-chains of fibrin, abundant in the tissue. These results have allowed the development of new efficient immunochemical methods for the detection of ACPA. Some of them are already commercially available. These new methods have permitted the high diagnostic value of ACPA which are present very early in the course of the disease, and also their prognostic value, to be confirmed. ACPA detection should therefore prove to be also a very valuable tool to guide the choice of therapeutic strategies, from the earliest stages of the disease. The synthesis of ACPA in the rheumatoid synovial tissue and the existence therein of a specific antigenic target constitute a strong argument for the involvement of this specific immunological conflict in the pathophysiology of RA. Indeed, it could lead to activation of effector mechanisms with pro-inflammatory effects, thus to formation in the tissue of new fibrin deposits, secondarily citrullinated. We therefore, propose a new pathophysiological model accounting for the self-maintenance and chronicity of rheumatoid inflammation. Numerous questions about the pathophysiological significance of the autoimmune response to deiminated proteins in RA remain to be answered to confirm this model.

Clavel C, Nogueira L, Laurent L, Iobagiu C, Vincent C, Sebbag M, Serre G. · Unité Mixte de Recherche 5165 CNRS-Université Toulouse III, Institut Fédératif de Recherche 30 (IFR30) Toulouse, France. · Arthritis Rheum. · Pubmed #18311806 links to  free full text

Abstract: OBJECTIVE: Macrophage-derived tumor necrosis factor alpha (TNFalpha) is a dominant mediator of synovitis in rheumatoid arthritis (RA). This study was undertaken to assess whether and how immune complexes (ICs) formed by the interaction of disease-specific autoantibodies to citrullinated proteins (ACPAs) with their main synovial target antigen, citrullinated fibrin, contribute to TNFalpha production by macrophages. METHODS: An in vitro human model was developed in which monocyte-derived macrophages were stimulated with ACPA-containing ICs that were generated by capturing ACPAs from RA sera on immobilized citrullinated fibrinogen. Cellular activation was evaluated by TNFalpha assay in culture supernatants. Selective blockade of IC interactions with the 3 classes of Fcgamma receptors (FcgammaR) was used to assess the contribution of each receptor to macrophage activation. In addition, 2 citrullinated fibrin-derived peptides bearing major ACPA epitopes were tested for their capacity to inhibit formation of macrophage-activating ACPA-containing ICs. RESULTS: ACPA-containing ICs induced a dose-dependent TNFalpha secretion by macrophages from 14 of 20 healthy donors. The macrophage response was systematically higher than that of the paired monocyte precursors. TNFalpha secretion was not reduced by blockade of FcgammaRI or FcgammaRIII, but was strongly repressed when interaction of ICs with FcgammaRII was prevented. The 2 citrullinated peptides significantly inhibited ACPA reactivity to citrullinated fibrinogen and, when tested together, almost completely abolished formation of macrophage-activating ICs, thereby diminishing the secreted TNFalpha levels. CONCLUSION: Our model demonstrates the inflammatory potential of ACPA-containing ICs via engagement of FcgammaRIIa at the surface of macrophages, strongly supporting their pathophysiologic involvement. Continuing dissection of these molecular pathways could open the way to new therapeutic approaches in patients with RA.

Guis S, Balandraud N, Bouvenot J, Auger I, Toussirot E, Wendling D, Mattei JP, Nogueira L, Mugnier B, Legeron P, Landt O, Serre G, Roudier J, Roudier C. · INSERM UMR 639 and Assistance Publique Hôpitaux de Paris, Hôpital de la Conception, Marseille, France. · Arthritis Rheum. · Pubmed #18050183 links to  free full text

Abstract: OBJECTIVE: To determine whether the -308 A/G tumor necrosis factor alpha (TNFalpha) gene polymorphism can predict the outcome of etanercept therapy in 86 patients with rheumatoid arthritis (RA), as already observed in patients treated with infliximab. METHODS: Eighty-six RA patients treated with etanercept were genotyped for -308 A/G TNFalpha gene polymorphism by polymerase chain reaction and melting curve analysis, using specific gene primers and probes. Patients were subdivided into group A (G/A genotype) and group G (G/G genotype). We compared clinical responses to etanercept between groups A and G after 6 months, using the Disease Activity Score in 28 joints (DAS28). After 12-month treatment, 48 of 86 patients were evaluated again. RESULTS: Of 86 patients, 18 (21%) belonged in group A and 68 (79%) belonged in group G. After 6-month treatment, 55.6% of patients in group A and 82.4% of patients in group G had DAS28 improvement >1.2 (P = 0.027 by chi-square). The mean +/- SD DAS28 improvement was 1.69 +/- 1.31 in group A and 2.23 +/- 1.19 in group G (P = 0.098 by t-test). After 1-year treatment 48 patients were tested again: 10 (21%) belonged in group A and 38 (79%) belonged in group G. Forty percent of patients in group A and 87% in group G had DAS28 improvement >1.2 (P = 0.005 by chi-square). The mean +/- SD DAS28 improvement was 1.334 +/- 1.37 in group A and 2.29 +/- 1.47 in group G (Mann-Whitney U test = 115, P = 0.0057). CONCLUSION: RA patients with a -308 G/G TNFalpha genotype respond to etanercept better than patients with a -308 A/G genotype.

Vander Cruyssen B, Nogueira L, Van Praet J, Deforce D, Elewaut D, Serre G, De Keyser F. · Department of Rheumatology, Ghent University Hospital, B-9000 Gent, Belgium. · Ann Rheum Dis. · Pubmed #17644546 No free full text.

Abstract: BACKGROUND: Different methods exist to demonstrate anti-citrullinated protein/peptide antibodies (ACPA). AIMS: To evaluate discrepancy between four ACPA tests. PATIENTS AND METHODS: Population 1 consisted of patients with a new diagnostic problem, including 86 patients with rheumatoid arthritis (RA) and 450 patients without RA. Population 2 consisted of 155 patients with RA who had long-standing disease. Population 3 consisted of 188 patients with psoriatic arthritis and in population 4 there were 192 patients with systemic lupus erythematosus. Populations 1 and 2 were tested with the anti-human fibrinogen antibody (AhfibA) test, anti-CCP2 from Eurodiagnostica (CCP2-euro), anti-CCP2 from Pharmacia (CCP2-phar) and anti-CCP3 test by Inova (CCP3). Samples were annotated as discrepant if positive in one and negative in at least one other test. Each discrepant sample was re-analysed in a different run. Populations 3 and 4 were analysed in the CCP2-euro and AhFibA test. RESULTS: In population 1, ACPA positivity was found in 17 of 450 (3.8%) patients without RA; 14 (82%) of these 17 samples were discrepant. In contrast, 61 of 86 (70.9%) patients with RA were ACPA positive of whom 18 of 61 (29.5%) were discrepant (70.9% vs. 29.5%, p<0.001). The discrepancies between tests could be partly attributed to borderline results, inter-assay discrepancy and inter-test variability. They were more prevalent in patients with systemic lupus erythematosus who were ACPA positive than in those with psoriatic arthritis who were ACPA positive. CONCLUSIONS: Discrepancy between different ACPA tests was observed attributable to the occurrence of borderline results, inter-assay variability and mainly to inter-test variability. The lowest inter-test discrepancy is observed between tests that use the same substrate.

Gourraud PA, Dieudé P, Boyer JF, Nogueira L, Cambon-Thomsen A, Mazières B, Cornélis F, Serre G, Cantagrel A, Constantin A. · Service d'Epidémiologie CHU Toulouse, INSERM, U558, Université Paul Sabatier Toulouse III, Faculté de Médecine, 37 allées Jules Guesde, Toulouse Cedex 7, 31073, France. · Arthritis Res Ther. · Pubmed #17328818 links to  free full text

Abstract: The HLA-DRB1 gene was reported to be associated with anticitrullinated protein/peptide autoantibody (ACPA) production in rheumatoid arthritis (RA) patients. A new classification of HLA-DRB1 alleles, reshaping the shared epitope (SE) hypothesis, was recently found relevant in terms of RA susceptibility and structural severity. We investigated the relevance of this new classification of HLA-DRB1 SE+ alleles in terms of rheumatoid factor (RF) and ACPA production in a sample of French RA patients. We studied 160 early RA patients included in a prospective longitudinal cohort of French Caucasian patients with recent-onset arthritis. RF, anticyclic citrullinated peptide 2 (anti-CCP2) and antideiminated human fibrinogen autoantibodies (AhFibA) were assessed in all patients at inclusion. The HLA-DRB1 gene was typed by PCR-sequence specific oligonucleotides probes (PCR-SSOP), and SE+ alleles were classified into four groups (S1, S2, S3P, S3D) according to the new classification. The new classification of HLA-DRB1 SE+ alleles distinguishes predisposing and protective alleles for RF, anti-CCP2 or AhFibA production. The presence of S2 or S3P alleles is associated with both RF, anti-CCP2 or AhFibA positivity, whereas the presence of S3D or S1 alleles appears to be protective for RF, anti-CCP2 or AhFibA positivity. The new classification of HLA-DRB1 SE+ alleles is relevant in terms of autoantibody production in early RA patients by differentiating predisposing and protective alleles for RF or ACPA production.

Vander Cruyssen B, Cantaert T, Nogueira L, Clavel C, De Rycke L, Dendoven A, Sebag M, Deforce D, Vincent C, Elewaut D, Serre G, De Keyser F. · Department of Rheumatology, Ghent University Hospital, Ghent, Belgium. · Arthritis Res Ther. · Pubmed #16859515 links to  free full text

Abstract: We studied the diagnostic performance of the anti-human citrullinated fibrinogen antibody (AhFibA) ELISA for rheumatoid arthritis (RA) in a consecutive cohort (population 1) and evaluated the agreement between the AhFibA ELISA and four other assays for anti-citrullinated protein/peptide antibodies (ACPAs) as well as rheumatoid factor in patients with longstanding RA (population 2). Population 1 consisted of 1024 patients with rheumatic symptoms; serum samples from these patients were sent to our laboratory for ACPA testing within the context of a diagnostic investigation for RA. Ninety-two of these patients were classified as having RA according to the American College of Rheumatology criteria and 463 were classified as non-RA patients. Population 2 consisted of 180 patients with longstanding RA and was used to assess agreement and correlations between five ACPA assays: anti-cyclic citrullinated peptide (CCP)1 and anti-CCP2 antibodies were detected using a commercially available ELISA, AhFibA using ELISA, and anti-PepA and anti-PepB antibodies using line immunoassay. Applying previously proposed cut-offs for AhFibA, we obtained a sensitivity of 60.9% and a specificity of 98.7% in population 1. Receiver operating characteristic curve analysis could not detect a significant difference in diagnostic performance between the AhFibA ELISA and anti-CCP2 assay. Performing a hierarchical nearest neighborhood cluster analysis of the five different ACPA assays in population 2, we identified two clusters: a cluster of anti-pepA, anti-pepB and anti-CCP1, and a cluster of AhFibA and anti-CCP2. In conclusion, we found that AhFibA and anti-CCP2 antibodies had similar diagnostic performance. However, disagreement between ACPA tests may occur.

Sebbag M, Moinard N, Auger I, Clavel C, Arnaud J, Nogueira L, Roudier J, Serre G. · Laboratory of "Epidermis Differentiation and Rheumatoid Autoimmunity", UMR 5165 CNRS-Toulouse III University, IFR30 (CNRS-INSERM-Université Paul Sabatier-CHU de Toulouse), Toulouse, France. · Eur J Immunol. · Pubmed #16838278 No free full text.

Abstract: Formation of the epitopes recognized by the rheumatoid arthritis (RA)-specific autoantibodies to citrullinated proteins (ACPA) on filaggrin and on the alpha- and beta-chains of fibrin, their synovial target, requires conversion of their arginyl residues into citrullyl residues, but is also affected by their amino-acyl environment. Using competition with five citrullinated filaggrin-derived peptides bearing major ACPA epitopes, we confirmed the close cross-reactivity between filaggrin and citrullinated fibrin. To identify the sequential epitopes recognized on fibrin by ACPA, 71 citrullinated 15-mer peptides derived from all the sites of the alpha- and beta-chains of fibrin harboring arginyl residues were tested by ELISA using ACPA-positive RA sera exhibiting different reactivity profiles to the five filaggrin peptides. We identified 18 fibrin-derived peptides bearing ACPA epitopes. Regarding the ability of fibrinogen arginyl residues to be citrullinated in vitro, 11 of the peptides likely correspond to in vivo targeted epitopes. Two out of them bear major epitopes and are located in the central globular domain of the protein. In the synovial tissue, fibrin citrullination and ACPA binding could impair fibrin degradation by plasmin. The immunological conflict between ACPA and fibrin could therefore sustain synovial inflammation not only via pro-inflammatory effector mechanisms but also via impairment of fibrinolysis.

Auger I, Sebbag M, Vincent C, Balandraud N, Guis S, Nogueira L, Svensson B, Cantagrel A, Serre G, Roudier J. · INSERM UMR 639, La Conception Hospital, Faculté de Médecine, 27 Boulevard Jean Moulin, 13005 Marseille, France. · Arthritis Rheum. · Pubmed #16255019 links to  free full text

Abstract: OBJECTIVE: Antibodies directed against citrullinated fibrinogen are highly specific for rheumatoid arthritis (RA). This study was undertaken to test whether RA-associated HLA-DR alleles are associated with anti-citrullinated fibrinogen in RA patient sera and whether replacement of arginyl by citrullyl residues on fibrinogen peptides modifies their binding to HLA-DR molecules and their recognition by T cells. METHODS: Antikeratin, antifilaggrin, and anti-citrullinated fibrinogen antibodies were assayed in RA patients who had undergone HLA-DR typing. Direct assays were performed to investigate binding of citrullinated or native fibrinogen peptides (encompassing the entire alpha- and beta-chains of fibrinogen) to purified HLA-DR molecules. T cell proliferative responses to citrullinated or native fibrinogen peptides were measured in RA patients and controls. RESULTS: HLA-DRB1*0404 was associated with anti-citrullinated fibrinogen in RA sera (P = 0.002). For the RA-associated alleles HLA-DRB1*0401 and HLA-DR1, there was a nonsignificant trend toward association (P = 0.07). Multiple peptides from the alpha- and beta-chains of fibrinogen bound many HLA-DR alleles; DRB1*0404 was the best fibrinogen peptide binder. Citrullination did not influence fibrinogen peptide binding to HLA-DR or fibrinogen peptide recognition by T cells. Peripheral blood T cells that recognized native or citrullinated fibrinogen peptides were common in RA patients but not in healthy controls. CONCLUSION: The RA-associated HLA-DRB1*0404 allele is also associated with production of antibodies to citrullinated fibrinogen. DRB1*0401 and DRB1*01 tend to be associated with anti-citrullinated fibrinogen, but this is not statistically significant. Citrullination of fibrinogen peptide does not influence peptide-DR-T cell interaction. Finally, T cell proliferation in response to citrullinated or uncitrullinated fibrinogen peptides is frequent in RA patients and very infrequent in controls.

Chapuy-Regaud S, Nogueira L, Clavel C, Sebbag M, Vincent C, Serre G. · Laboratory of 'Epidermis Differentiation and Rheumatoid Autoimmunity', UMR 5165 CNRS-Toulouse III University, Toulouse, France. · Clin Exp Immunol. · Pubmed #15730401 links to  free full text

Abstract: In the rheumatoid synovium, deiminated ('citrullinated') forms of fibrin are the major targets of IgG autoantibodies to citrullinated proteins (ACPA), the most specific serological markers of rheumatoid arthritis (RA). To further the characterization of ACPA, we determined their subclass distribution. From a previously validated highly sensitive and specific enzyme-linked immunosorbent assay (ELISA) onto in vitro deiminated human fibrinogen - antihuman fibrin(ogen) autoantibodies (AhFibA)-ELISA - we derived and calibrated four ELISAs, using monoclonal antibodies to each of the four IgG subclasses, to determine the proportions of AhFibA subclasses in the sera. A series of 186 serum samples from RA patients was analysed. All AhFibA-positive sera contained IgG1-AhFibA, which reached the highest titres and accounted for more than 80% of AhFibA in three-quarters of the sera. One or two other subclasses were associated with IgG1 in 39% of the sera, IgG4-AhFibA being observed much more frequently and at higher titres than IgG3- or IgG2-AhFibA. IgG1 alone or IgG(1 + 4)-AhFibA were the AhFibA subclass profiles found in more than 80% of patients. AhFibA are mainly IgG1 and, to a lesser extent, IgG4. Such IgG subclass profiles may influence the effector phases of the immunological conflict between ACPA and deiminated fibrin that takes place specifically in the rheumatoid synovium and therefore may play a critical role in the self-maintenance of rheumatoid inflammation.

Vincent C, Nogueira L, Sebbag M, Chapuy-Regaud S, Arnaud M, Letourneur O, Rolland D, Fournié B, Cantagrel A, Jolivet M, Serre G. · Institut National de la Santé et de la Recherche Médicale (CJF 96-02, IFR30), Purpan School of Medicine, University of Toulouse III, Toulouse, France. · Arthritis Rheum. · Pubmed #12209508 links to  free full text

Abstract: OBJECTIVE: To assay antifilaggrin autoantibodies, we developed an enzyme-linked immunosorbent assay (ELISA) using a "citrullinated" recombinant rat filaggrin. Our objectives were to assess its value for diagnosing rheumatoid arthritis (RA) and to compare the results with those obtained using 4 other reference methods for detection of antifilaggrin autoantibodies, including the commercially available ELISA that uses a modified "citrullinated" synthetic peptide derived from the sequence of human filaggrin (CCP-ELISA). METHODS: We analyzed 711 sera from patients with well-characterized rheumatic diseases, including 240 patients with RA. Antifilaggrin autoantibodies were detected by an ELISA using a recombinant rat filaggrin deiminated in vitro as immunosorbent (ArFA-ELISA). The results considered were the differences between the optical densities obtained on deiminated and nondeiminated proteins. Antibodies to rat esophagus epithelium were detected by indirect immunofluorescence, while antibodies to human filaggrin were detected by immunoblotting and by a recently described ELISA using a deiminated recombinant human filaggrin. Finally, CCP-ELISA was performed according to the manufacturer's recommendations. RESULTS: At the titer thresholds allowing diagnostic specificities of 0.95, 0.985, and 0.99 to be reached, the diagnostic sensitivities of the ArFA-ELISA were 0.76, 0.67, and 0.65, respectively. At these 3 thresholds, the sensitivities were significantly higher than those of the 4 other tests. Despite incomplete overlapping of the 5 tests, the high diagnostic performance of the ArFA-ELISA allows us to propose this test to replace all the other methods for antifilaggrin autoantibody detection. CONCLUSION: ArFA-ELISA appears to be the most efficient test among those available for the detection of antifilaggrin autoantibodies, in terms of diagnostic accuracy for RA. Its diagnostic performance in early RA and its prognostic value are currently under evaluation.

Nogueira L, Sebbag M, Vincent C, Arnaud M, Fournié B, Cantagrel A, Jolivet M, Serre G. · Department of Biology and Pathology of the Cell, Institut National de la Santé et de la Recherche Médicale (CJF 96-02), Toulouse-Purpan School of Medicine, University of Toulouse III (IFR Claude de Préval, INSERM-CNRS-UPS - CHU), France. · Ann Rheum Dis. · Pubmed #11502616 links to  free full text

Abstract: OBJECTIVE: To develop a standardisable enzyme linked immunosorbent assay (ELISA), using human filaggrin, for detection of antifilaggrin autoantibodies in rheumatoid arthritis (RA). To compare the diagnostic performance of the ELISA with those of reference tests: "antikeratin antibodies" ("AKA"), and antibodies to human epidermis filaggrin detected by immunoblotting (AhFA-IB). METHODS: Two ELISAs were developed using either affinity purified neutral-acidic human epidermis filaggrin (AhFA-ELISA-pur) or a recombinant human filaggrin deiminated in vitro (AhFA-ELISA-rec) as immunosorbent. Antifilaggrin autoantibodies were assayed in 714 serum samples from patients with well characterised rheumatic diseases, including 241 RA and 473 other rheumatic diseases, using the two ELISAs. "AKA" and AhFA-IB tests were carried out in the same series of patients. The diagnostic performance of the four tests was compared and their relationships analysed. RESULTS: The titres of "AKA", AhFA-IB, and the AhFA-ELISAs correlated strongly with each other. The diagnostic sensitivity of the AhFA-ELISA-rec, which was better than that of AhFA-ELISA-pur, was 0.52 for a specificity of 0.95. This performance was similar to those of "AKA" or AhFA-IB. However, combining AhFA-ELISA-rec with AhFA-IB led to a diagnostic sensitivity of 0.55 for a specificity of 0.99. CONCLUSION: A simple and easily standardisable ELISA for detection of antifilaggrin autoantibodies was developed and validated on a large series of patients using a citrullinated recombinant human filaggrin. The diagnostic performance of the test was similar to that of the "AKA" and AhFA-IB. Nevertheless, combining the AhFA-ELISA-rec with one of the other tests clearly enhanced the performance.

Masson-Bessière C, Sebbag M, Girbal-Neuhauser E, Nogueira L, Vincent C, Senshu T, Serre G. · Department of Biology and Pathology of the Cell, Institut National de la Santé et de la Recherche Médicale Contrat Jeune Formation 96-02, Toulouse-Purpan School of Medicine, University Toulouse III, Toulouse, France. · J Immunol. · Pubmed #11238669 links to  free full text

Abstract: IgG antifilaggrin autoantibodies (AFA) are the most specific serological markers of rheumatoid arthritis. In epithelial tissues, they recognize citrulline-bearing epitopes present on various molecular forms of (pro)filaggrin. Histological analysis of rheumatoid synovial membranes with an Ab to citrulline showed labeling of interstitial amorphous deposits and mononuclear cells of various types. Immunochemical analysis of exhaustive sequential extracts of the same tissues showed that they contain several deiminated (citrulline containing) proteins. Among them, two proteins, p64--78 and p55--61, present in urea-DTT and guanidine extracts, were shown by immunoblotting to be specifically targeted by AFA. By amino-terminal sequencing the proteins were identified as deiminated forms of the alpha- and beta-chains of fibrin, respectively. Their identity was confirmed using several Abs specific for the A alpha- and/or to the B beta-chain of fibrin(ogen). Moreover, AFA-positive rheumatoid arthritis (RA) sera and purified AFA were highly reactive to the A alpha- and B beta-chains of human fibrinogen only after deimination of the molecules by a peptidylarginine deiminase. Autoantibodies affinity purified from a pool of RA sera onto deiminated fibrinogen were reactive toward all of the epithelial and synovial targets of AFA. This confirmed that the autoantibodies to the deiminated A alpha-and B beta-chains of fibrinogen, the autoantibodies to the synovial proteins p64--78 and p55--61, and, lastly, AFA, constitute largely overlapping autoantibody populations. These results show that deiminated forms of fibrin deposited in the rheumatoid synovial membranes are the major target of AFA. They suggest that autoimmunization against deiminated fibrin is a critical step in RA pathogenesis.

Masson-Bessière C, Sebbag M, Durieux JJ, Nogueira L, Vincent C, Girbal-Neuhauser E, Durroux R, Cantagrel A, Serre G. · Department of Biology and Pathology of the Cell, Institut National de la Santé et de la Recherche Médicale (CJF 96-02), Toulouse-Purpan School of Medicine, University of Toulouse III, France. · Clin Exp Immunol. · Pubmed #10691929 links to  free full text

Abstract: IgG anti-filaggrin autoantibodies (AFA) are the most specific serological markers of rheumatoid arthritis (RA). They include the so-called 'anti-keratin antibodies' (AKA) and anti-perinuclear factor (APF), and recognize human epidermal filaggrin and other (pro)filaggrin-related proteins of various epithelial tissues. In this study we demonstrate that AFA are produced in rheumatoid synovial joints. In 31 RA patients, AFA levels were assayed at equal IgG concentrations in paired synovial fluids (SF) and sera. AFA titre-like values determined by indirect immunofluorescence and immunoblotting and AFA concentrations determined by ELISA were non-significantly different in serum and SF, clearly indicating that AFA are not concentrated in SF. In contrast, we demonstrated that AFA are enriched in RA synovial membranes, since the ELISA-determined AFA in low ionic-strength extracts of synovial tissue from four RA patients represented a 7.5-fold higher proportion of total IgG than in paired sera. When small synovial tissue explants from RA patients were cultured for a period of 5 weeks, the profile of IgG and AFA released in the culture supernatants was first consistent with passive diffusion of the tissue-infiltrating IgG (including AFA) over the first day of culture, then with a de novo synthesis of IgG and AFA. Therefore, AFA-secreting plasma cells are present in the synovial tissue of RA patients and AFA can represent a significant proportion of the IgG secreted within the rheumatoid pannus.