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Int J Biol Sci 2013; 9(3):279-288. doi:10.7150/ijbs.5996

Research Paper

Interleukin-6 Receptor Blockade Selectively Reduces IL-21 Production by CD4 T Cells and IgG4 Autoantibodies in Rheumatoid Arthritis

Gustavo Carbone1, Augusta Wilson1, Sean A Diehl2, Janice Bunn3, Sheldon M. Cooper1, Mercedes Rincon1,2✉

1. Department of Medicine, Division of Rheumatology1 and Division of Immunobiology2, University of Vermont, Burlington, VT 05405;
2. Department of Medicine, Division of Immunobiology, University of Vermont, Burlington, VT 05405;
3. Department of Mathematics and Statistics, University of Vermont, Burlington, VT05405, USA.

Abstract

Interleukin-6 (IL-6) levels are known to be increased in patients with rheumatoid arthritis (RA). Tocilizumab, a monoclonal antibody to the IL-6 receptor (IL-6R), reduces disease activity in RA, although its mechanisms of action remain unclear. Since IL-6 regulates cytokine production by CD4 T cells during activation, we investigated whether treatment with tocilizumab altered the phenotype and cytokine production by CD4 T cells in patients with rheumatoid arthritis. We show here that tocilizumab treatment does not change the production of cytokines by naïve CD4 T cells. However, tocilizumab treatment causes a selective decrease of IL-21 production by memory/activated CD4 T cells. Since IL-21 is known to promote plasma cell differentiation, we examined the effect of tocilizumab on the production of autoantibodies. We show that there is a decrease in the levels of IgG4 anti-CCP antibodies, but there is no effect on IgG1 anti-CCP antibodies. In addition, we show that IL-21 is a powerful inducer of IgG4 production by B cells. Thus, IL-6 contributes to the presence of IgG4-specific anti-CCP autoantibodies in RA patients, likely through its effect on IL-21 production by CD4 T cells, and IL-6R blockade down-regulates this pathway.

Keywords: Interleukin-6, IL-6, IL-21, CD4 T, rheumatoid arthritis, IgG4, auti-CCP, tocilizumab

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How to cite this article:
Carbone G, Wilson A, Diehl SA, Bunn J, Cooper SM, Rincon M. Interleukin-6 Receptor Blockade Selectively Reduces IL-21 Production by CD4 T Cells and IgG4 Autoantibodies in Rheumatoid Arthritis. Int J Biol Sci 2013; 9(3):279-288. doi:10.7150/ijbs.5996. Available from http://www.ijbs.com/v09p0279.htm