title: Activated memory B cells may function as antigen-presenting cells in the joints of children with juvenile idiopathic arthritis.
abstract: OBJECTIVE
  B cells impact the perpetuation of chronic inflammatory or autoimmune diseases in multiple ways. A role of B cells as antigen-presenting cells (APCs) in the pathogenesis of chronic arthritis in humans has been suggested; however, as of yet the presence of such B cells at the site of inflammation has not been demonstrated. This study was undertaken to investigate whether synovial B cells in patients with juvenile idiopathic arthritis (JIA) might display features of APCs.
  
  
  METHODS
  The frequency, phenotype, and immunoglobulin repertoire of synovial B cells were studied by flow cytometry and single-cell polymerase chain reaction (PCR). Cytokine expression by B cells was analyzed by real-time PCR, and interaction between B cells and T cells was investigated in a mixed lymphocyte culture.
  
  
  RESULTS
  CD27+IgD- and CD27-IgD- B cells accumulated in the joints of JIA patients and displayed an activated phenotype. Both B cell subsets expressed hypermutated and class-switched immunoglobulins, indicators of memory B cells. The accumulating memory B cells expressed the costimulatory molecules CD80/CD86 and showed a higher capacity to activate allogeneic T cells and prime a Th1 phenotype than their peripheral blood counterparts.
  
  
  CONCLUSIONS
  Activated immunoglobulin class-switched CD27- and CD27+ memory B cells, indicating a phenotype of APCs with expression of costimulatory molecules, accumulate in the joints of patients with JIA and might be involved in the amplification of pathogenic T cell activation. These findings provide evidence that B cells play an antibody-independent immunopathologic role in human chronic inflammatory arthritis of childhood.
authors.affiliation: Vivantes Children's Hospital, Berlin-Friedrichshain, Germany): Children's Hospital and University of Würzburg, Würzburg, Germany. Morbach_H@klinik.uni-wuerzburg.de
authors.forename: Henner
authors.initials: H
authors.lastname: Morbach
authors.forename: Verena
authors.initials: V
authors.lastname: Wiegering
authors.forename: Petra
authors.initials: P
authors.lastname: Richl
authors.forename: Tobias
authors.initials: T
authors.lastname: Schwarz
authors.forename: Nadine
authors.initials: N
authors.lastname: Suffa
authors.forename: Eva-Maria
authors.initials: EM
authors.lastname: Eichhorn
authors.forename: Matthias
authors.initials: M
authors.lastname: Eyrich
authors.forename: Hermann J
authors.initials: HJ
authors.lastname: Girschick
mesh_terms: D000938:Antigen-Presenting Cells / Q000276:immunology*; D001171:Arthritis, Juvenile / Q000276:immunology* / Q000378:metabolism; D016175:B-Lymphocyte Subsets / Q000276:immunology*; D002648:Child; D002675:Child, Preschool; D016207:Cytokines / Q000378:metabolism; D005260:Female; D006801:Humans; D007156:Immunologic Memory; D007596:Joints / Q000276:immunology*; D008297:Male; D013582:Synovial Fluid / Q000276:immunology / Q000378:metabolism; D013583:Synovial Membrane / Q000276:immunology* / Q000378:metabolism
chemical_list: D016207:Cytokines