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Medline ® Abstract for Reference 164

of 'Juvenile idiopathic arthritis: Epidemiology and immunopathogenesis'

Activated memory B cells may function as antigen-presenting cells in the joints of children with juvenile idiopathic arthritis.
Morbach H, Wiegering V, Richl P, Schwarz T, Suffa N, Eichhorn EM, Eyrich M, Girschick HJ
Arthritis Rheum. 2011;63(11):3458.
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.
CONCLUSION: 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.
Vivantes Children's Hospital, Berlin-Friedrichshain, Germany): Children's Hospital and University of Würzburg, Würzburg, Germany. Morbach_H@klinik.uni-wuerzburg.de