B Cell–Specific Expression of Inducible Costimulator Ligand Is Necessary for the Induction of Arthritis in Mice

Authors


Abstract

Objective

Inducible costimulator (ICOS)–ICOSL interactions are necessary for activation of Teff cells and follicular helper T (Tfh) cells. ICOSL is expressed on B cells, macrophages, and dendritic cells and can be induced on nonhematopoietic cells. The aim of this study was to determine whether expression of ICOSL on B cells is necessary for the development of proteoglycan (PG)–induced arthritis (PGIA).

Methods

PGIA was initiated by immunizing wild-type and ICOSL-deficient (ICOSL−/−) or B cell–specific ICOSL−/− chimeric BALB/c mice with human PG in adjuvant. The onset and severity of arthritis were monitored over time. CD4+ T cell proliferation and CD4+ T cell cytokine production were measured in vitro after the cells were restimulated with PG. Germinal center (GC) B cells, plasma cells, Tfh cells, and Treg cells were identified by staining with specific antibodies.

Results

Arthritis progression was completely inhibited in both ICOSL−/− mice and B cell–specific ICOSL−/− chimeric mice. Production of the Teff cell–produced cytokines interferon-γ and interleukin-17 (IL-17) and the antiinflammatory cytokine IL-4 was suppressed. The reduced percentages of GCs and Tfh cells and the decreased production of IL-21 correlated with a decrease in the anti-mouse PG antibody response. However, the percentage of plasma cells was not reduced despite a reduction in IgG responses.

Conclusion

These data indicate that the signals provided by ICOSL-expressing B cells to Teff cells and Tfh cells are necessary for the development of arthritis. Thus, therapeutic blockade of ICOSL−ICOS interactions may be an effective strategy for the treatment of rheumatoid arthritis.

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