Extended report Ann Rheum Dis 2010;69:1697–1703. doi:10.1136/ard.2009.122655 1697 ABSTRACT Objectives Interleukin 33 (IL-33) is a new member of the IL-1 family of cytokines which signals via its receptor, ST2 (IL-33R), and has an important role in Th2 and mast cell responses. This study shows that IL-33 orchestrates neutrophil migration in arthritis. Methods and results Methylated bovine serum albumin (mBSA) challenge in the knee joint of mBSA-immunised mice induced local neutrophil migration accompanied by increased IL-33R and IL-33 mRNA expression. Cell migration was inhibited by systemic and local treatments with soluble (s)IL-33R, an IL-33 decoy receptor, and was not evident in IL-33R-deficient mice. IL-33 injection also induced IL-33R-dependent neutrophil migration. Antigen- and IL-33-induced neutrophil migration in the joint was dependent on CXCL1, CCL3, tumour necrosis factor α (TNFα) and IL-1β synthesis. Synovial tissue, macrophages and activated neutrophils expressed IL-33R. IL-33 induces neutrophil migration by activating macrophages to produce chemokines and cytokines and by directly acting on neutrophils. Importantly, neutrophils from patients with rheumatoid arthritis successfully treated with anti-TNFα antibody (infliximab) expressed significantly lower levels of IL-33R than patients treated with methotrexate alone. Only neutrophils from patients treated with methotrexate alone or from normal donors stimulated with TNFα responded to IL-33 in chemotaxis. Conclusions These results suggest that suppression of IL-33R expression in neutrophils, preventing IL-33-induced neutrophil migration, may be an important mechanism of anti-TNFα therapy of inflammation. INTRODUCTION The interleukin 1 (IL-1) family of cytokines includes 11 members classified systematically as IL-1F1 to IL-1F11. 1 IL-33 is the latest member of the family and is also known as IL-1F11. 1 2 IL-33 is structur- ally related to IL-1β and IL-18 and was found to have strong biological relevance in immune and inflammatory reactions. 2 However, unlike IL-1β and IL-18, which mainly promote Th1-/Th17- associated responses, IL-33 enhanced IL-5 and IL-13 production by polarised Th2. 2 3 In addition, administration of IL-33 into naïve mice provoked innate type II cytokine and IgE production. 2 IL-33 signals via a heterodimeric receptor—the α-chain IL-33R 2 and the β-chain IL-1RAcP 4 5 —and triggers the activation of NFκB, MAP kinases p38, ERK1/2, JNK1/2 in mast cells 2 and T cells. 3 There are two isoforms of the IL-33R protein encoded by the st2 gene and resultant alternative IL-33 induces neutrophil migration in rheumatoid arthritis and is a target of anti-TNF therapy Waldiceu A Verri Jr, 1,2 Fabrício O Souto, 3 Silvio M Vieira, 1 Sergio C L Almeida, 4 Sandra Y Fukada, 1,5 Damo Xu, 5 Jose C Alves-Filho, 1,5 Thiago M Cunha, 1 Ana T G Guerrero, 1 Rafaela B Mattos-Guimaraes, 1 Fabíola R Oliveira, 4 Mauro M Teixeira, 6 João S Silva, 7 Iain B McInnes, 5 Sergio H Ferreira, 1 Paulo Louzada-Junior, 4 Foo Y Liew, 5 Fernando Q Cunha 1 ▶ Additional data are published online only. To view these files please visit the journal online (http://ard.bmj.com). 1 Department of Pharmacology, School of Medicine of Ribeirao Preto, University of Sao Paulo, Sao Paulo, Brazil 2 Departamento de Ciências Patológicas, CCB, Universidade Estadual de Londrina, Londrina, Brazil 3 Department of Surgery and Anatomy, School of Medicine of Ribeirao Preto, University of Sao Paulo, Sao Paulo, Brazil 4 Division of Clinical Immunology, School of Medicine of Ribeirao Preto, University of Sao Paulo, Sao Paulo, Brazil 5 Division of Immunology, Infection and Inflammation, University of Glasgow, Glasgow, UK 6 Departamento de Bioquímica e Imunologia, Universidade Federal de Minas Gerais, Minas Gerais, Brazil 7 Department of Biochemistry and Immunology, School of Medicine of Ribeirao Preto, University of Sao Paulo, Sao Paulo, Brazil Correspondence to Waldiceu A Verri Jr, Universidade Estadual de Londrina, Rod. Celso Garcia Cid KM380 PR445, Londrina 86051990, Brazil; waverri@uel.br or waldiceujr@yahoo.com.br Accepted 31 January 2010 gene splicing: IL-33RL, a transmembrane form, and soluble IL-33R (sIL-33R), 6 a secreted form which can serve as a decoy receptor for IL-33. 2 7 IL-33RL is preferentially expressed on a subset of Th2 cells but not Th1 cells 8 9 and can profoundly modulate innate and adaptive immunity. 10 11 IL-33R is also expressed on mast cells, macrophages and fibro- blasts. 2 Soluble IL-33R is a potent inhibitor of col- lagen-induced arthritis (CIA) in mice, 7 suggesting that IL-33–IL-33R signalling is a key pathway in the context of rheumatoid arthritis (RA). We have also shown that IL-33 contributes to the develop- ment of local inflammatory cutaneous and articular mechanical hypernociception (inflammatory pain) in a murine model of RA via interferon γ (IFNγ) production in vivo. 12 IL-33 can also induce IFNγ production by Th1 lymphocytes, invariant natural killer-like T (NKT) and natural killer (NK) cells. 13 14 As neutrophils contribute importantly to the development of pain, 15–18 inflammation and tissue destruction in RA, 19–22 we investigated whether IL-33 has a role in arthritis by enhancing neutrophil migration to inflamed joints. MATERIALS AND METHODS Details are given in the online supplement. Mice BALB/c, C57BL/6, IL-33R –/– , TNFR1 –/– , CCL3 –/– and mast cell-deficient (WBB6F1–w/w (v)) mice were bred and maintained in the Faculty of Medicine of Ribeirao Preto (FMRP). Clinical samples Peripheral blood samples were collected from eight healthy volunteers, four patients treated with methotrexate (MTX) and nine treated with MTX plus anti-tumour necrosis factor (anti-TNF). Neutrophils were purified and IL-33R expression was determined by quantitative PCR (qPCR) before or after culturing with TNFα. Purified neutrophils were also examined for their chemotaxis to IL-33 in a Boyden chamber. Immunisation and neutrophil migration Mice were immunised with methylated bovine serum albumin (mBSA) in complete Freund’s adju- vant (CFA). Sham immunised mice received CFA only. Mice were challenged with mBSA or IL-33 on day 21. 12 Knee joints cells were harvested, the total number of infiltrating cells was determined in group.bmj.com on May 31, 2013 - Published by ard.bmj.com Downloaded from