RT Journal Article SR Electronic T1 Plasma Levels of Eicosapentaenoic Acid Are Associated with Anti-TNF Responsiveness in Rheumatoid Arthritis and Inhibit the Etanercept-driven Rise in Th17 Cell Differentiation in Vitro JF The Journal of Rheumatology JO J Rheumatol FD The Journal of Rheumatology SP jrheum.161068 DO 10.3899/jrheum.161068 A1 Louisa Jeffery A1 Helena L. Fisk A1 Philip C. Calder A1 Andrew Filer A1 Karim Raza A1 Christopher D. Buckley A1 Iain McInnes A1 Peter C. Taylor A1 Benjamin A. Fisher YR 2017 UL http://www.jrheum.org/content/early/2017/02/09/jrheum.161068.abstract AB Objective To determine whether levels of plasma n-3 polyunsaturated fatty acids are associated with response to antitumor necrosis factor (anti-TNF) agents in rheumatoid arthritis (RA), and whether this putative effect may have its basis in altering anti-TNF–driven Th17 cell differentiation. Methods Plasma was collected at baseline and after 3 months of anti-TNF treatment in 22 patients with established RA, and fatty acid composition of the phosphatidylcholine (PC) component was measured. CD4+CD25– T cells and monocytes were purified from the blood of healthy donors and cocultured in the presence of anti-CD3, with or without etanercept (ETN), eicosapentaenoic acid (EPA), or the control fatty acid, linoleic acid (LA). Expression of interleukin 17 and interferon-γ was measured by intracellular staining and flow cytometry. Results Plasma PC EPA levels and the EPA/arachidonic acid ratio correlated inversely with change in the Disease Activity Score at 28 joints (DAS28) at 3 months (–0.51, p = 0.007 and –0.48, p = 0.01, respectively), indicating that higher plasma EPA was associated with a greater reduction in DAS28. Plasma PC EPA was positively associated with European League Against Rheumatism response (p = 0.02). An increase in Th17 cells post-therapy has been associated with nonresponse to anti-TNF. ETN increased Th17 frequencies in vitro. Physiological concentrations of EPA, but not LA, prevented this. Conclusion EPA status was associated with clinical improvements to anti-TNF therapy in vivo and prevented the effect of ETN on Th17 cells in vitro. EPA supplementation might be a simple way to improve anti-TNF outcomes in patients with RA by suppressing Th17 frequencies.