title: IgM and IgA rheumatoid factors purified from rheumatoid arthritis sera boost the Fc receptor- and complement-dependent effector functions of the disease-specific anti-citrullinated protein autoantibodies.
abstract: Rheumatoid factors (RF) and the disease-specific anti-citrullinated protein autoantibodies (ACPA) coexist in the joints of rheumatoid arthritis (RA) patients where they probably contribute to synovitis. We investigated the influence of IgM and IgA RF on the FcR- and complement-dependent effects of ACPA immune complexes (ACPA-IC). When stimulated by ACPA-IC formed in the presence of IgM RF or IgA RF fractions purified from RA serum pools, M-CSF-generated macrophages skewed their cytokine response toward inflammation, with increases in the TNF-α/IL-10 ratio and in IL-6 and IL-8 secretion, and decreases in the IL-1Ra/IL-1β ratio. In the IgM RF-mediated amplification of the inflammatory response of macrophages, the participation of an IgM receptor was excluded, notably by showing that they did not express any established receptor for IgM. Rather, this amplification depended on the IgM RF-mediated recruitment of more IgG into the ACPA-IC. However, the macrophages expressed FcαRI and blocking its interaction with IgA inhibited the IgA RF-mediated amplification of TNF-α secretion induced by ACPA-IC, showing its major implication in the effects of RF of the IgA class. LPS further amplified the TNF-α response of macrophages to RF-containing ACPA-IC. Lastly, the presence of IgM or IgA RF increased the capacity of ACPA-IC to activate the complement cascade. Therefore, specifically using autoantibodies from RA patients, the strong FcR-mediated or complement-dependent pathogenic potential of IC including both ACPA and IgM or IgA RF was established. Simultaneous FcR triggering by these RF-containing ACPA-IC and TLR4 ligation possibly makes a major contribution to RA synovitis.
authors.affiliation: Unité Différenciation Épidermique et Autoimmunité Rhumatoïde, Unité Mixte de Recherche 1056, INSERM, 31059 Toulouse Cedex 9, France; Unité Mixte de Recherche 5165, Centre National de la Recherche Scientifique, 31059 Toulouse Cedex 9, France; Université de Toulouse, 31059 Toulouse Cedex 9, France; and Laboratoire de Biologie Cellulaire et Cytologie, Centre Hospitalier Universitaire de Toulouse, 31059 Toulouse Cedex 9, France.
authors.forename: Florence
authors.initials: F
authors.lastname: Anquetil
authors.affiliation: Unité Différenciation Épidermique et Autoimmunité Rhumatoïde, Unité Mixte de Recherche 1056, INSERM, 31059 Toulouse Cedex 9, France; Unité Mixte de Recherche 5165, Centre National de la Recherche Scientifique, 31059 Toulouse Cedex 9, France; Université de Toulouse, 31059 Toulouse Cedex 9, France; and Laboratoire de Biologie Cellulaire et Cytologie, Centre Hospitalier Universitaire de Toulouse, 31059 Toulouse Cedex 9, France.
authors.forename: Cyril
authors.initials: C
authors.lastname: Clavel
authors.affiliation: Unité Différenciation Épidermique et Autoimmunité Rhumatoïde, Unité Mixte de Recherche 1056, INSERM, 31059 Toulouse Cedex 9, France; Unité Mixte de Recherche 5165, Centre National de la Recherche Scientifique, 31059 Toulouse Cedex 9, France; Université de Toulouse, 31059 Toulouse Cedex 9, France; and.
authors.forename: Géraldine
authors.initials: G
authors.lastname: Offer
authors.affiliation: Unité Différenciation Épidermique et Autoimmunité Rhumatoïde, Unité Mixte de Recherche 1056, INSERM, 31059 Toulouse Cedex 9, France; Unité Mixte de Recherche 5165, Centre National de la Recherche Scientifique, 31059 Toulouse Cedex 9, France; Université de Toulouse, 31059 Toulouse Cedex 9, France; and Laboratoire de Biologie Cellulaire et Cytologie, Centre Hospitalier Universitaire de Toulouse, 31059 Toulouse Cedex 9, France.
authors.forename: Guy
authors.initials: G
authors.lastname: Serre
authors.affiliation: Unité Différenciation Épidermique et Autoimmunité Rhumatoïde, Unité Mixte de Recherche 1056, INSERM, 31059 Toulouse Cedex 9, France; Unité Mixte de Recherche 5165, Centre National de la Recherche Scientifique, 31059 Toulouse Cedex 9, France; Université de Toulouse, 31059 Toulouse Cedex 9, France; and mireille.sebbag@inserm.fr.
authors.forename: Mireille
authors.initials: M
authors.lastname: Sebbag
mesh_terms: D001172:Arthritis, Rheumatoid / Q000276:immunology* / Q000473:pathology; D003167:Complement Activation / Q000187:drug effects* / Q000276:immunology; D003165:Complement System Proteins / Q000276:immunology*; D016207:Cytokines / Q000276:immunology*; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000302:isolation & purification / Q000494:pharmacology; D007075:Immunoglobulin M / Q000302:isolation & purification / Q000494:pharmacology; D007249:Inflammation / Q000139:chemically induced / Q000276:immunology / Q000473:pathology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000276:immunology* / Q000473:pathology; D008297:Male; D011961:Receptors, Fc / Q000276:immunology*; D012217:Rheumatoid Factor / Q000302:isolation & purification / Q000494:pharmacology; D013585:Synovitis / Q000276:immunology / Q000473:pathology
chemical_list: D016207:Cytokines; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D008070:Lipopolysaccharides; D011961:Receptors, Fc; D003165:Complement System Proteins; D012217:Rheumatoid Factor