title: Monoclonal anti-citrullinated protein antibodies selected on citrullinated fibrinogen have distinct targets with different cross-reactivity patterns.
abstract: OBJECTIVE
  ACPAs are thought to play a pathogenic role in RA. Because of their polyclonal nature it is difficult to study characteristics of ACPAs such as cross-reactivity or affinity. This study aimed to analyse the ACPA response at clonal level.
  
  
  METHODS
  Citrullinated fibrinogen-specific B cells were isolated from blood derived from an RA patient by fluorescent automated cell sorting (FACS). Antigen specificity was verified by ELISA of culture supernatant. RNA of antigen-specific B cells was isolated and VH and VL chains were cloned and subsequently expressed as IgG1 antibodies.
  
  
  RESULTS
  Two human recombinant antibodies were obtained that bind to citrullinated fibrinogen peptide (cFib). Both monoclonal antibodies originate from different naive B cells, undergo extensive somatic hypermutation and bind to cFib (but not to Fib) with moderate avidity. Furthermore, they show distinct cross-reactivity patterns towards other citrullinated peptides, suggesting that both antibodies have different primary targets.
  
  
  CONCLUSIONS
  Together these data suggest that ACPAs are formed by antigen-driven maturation, and that multiple citrullinated antigens are involved in activating the B-cell response.
authors.affiliation: Sanquin Research and Landsteiner Laboratorium, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Lotte A
authors.initials: LA
authors.lastname: van de Stadt
authors.forename: Pauline A
authors.initials: PA
authors.lastname: van Schouwenburg
authors.forename: Suzanne
authors.initials: S
authors.lastname: Bryde
authors.forename: Simone
authors.initials: S
authors.lastname: Kruithof
authors.forename: Dirkjan
authors.initials: D
authors.lastname: van Schaardenburg
authors.forename: Dörte
authors.initials: D
authors.lastname: Hamann
authors.forename: Gertjan
authors.initials: G
authors.lastname: Wolbink
authors.forename: Theo
authors.initials: T
authors.lastname: Rispens
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D000918:Antibody Specificity; D001172:Arthritis, Rheumatoid / Q000276:immunology*; D001323:Autoantibodies / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology*; D003429:Cross Reactions / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000276:immunology; D005340:Fibrinogen / Q000276:immunology*; D005434:Flow Cytometry; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D010456:Peptides, Cyclic / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D001323:Autoantibodies; D000939:Epitopes; D007074:Immunoglobulin G; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide; D005340:Fibrinogen