ORIGINAL ARTICLE EXPERIMENTAL ALLERGY AND IMMUNOLOGY Local receptor revision and class switching to IgE in chronic rhinosinusitis with nasal polyps P. Gevaert 1, *, K. T. Nouri-Aria 2, *, H. Wu 2,3,4 , C. E. Harper 3 , P. Takhar 3,4 , D. J. Fear 4 , F. Acke 1 , N. De Ruyck 1 , G. Banfield 2 , H. H. Kariyawasam 5 , C. Bachert 1 , S. R. Durham 2 & H. J. Gould 3,4 1 Upper Airways Research Laboratory, Department of Otorhinolaryngology, Ghent University, Ghent, Belgium; 2 Allergy & Clinical Immunology, National Heart & Lung Institute, Imperial College London; 3 Randall Division of Cell and Molecular Biophysics, King’s College London; 4 Division of Asthma, Allergy and Lung Biology, King’s College London; 5 Royal National Throat Nose and Ear Hospital, London, UK To cite this article: Gevaert P, Nouri-Aria KT, Wu H, Harper CE, Takhar P, Fear DJ, Acke F, De Ruyck N, Banfield G, Kariyawasam HH, Bachert C, Durham SR, Gould HJ. Local receptor revision and class switching to IgE in chronic rhinosinusitis with nasal polyps. Allergy 2013; 68: 55–63. Keywords allergic rhinitis; germinal center-like structures; IgE; nasal polyps; receptor revision. Correspondence Philippe Gevaert, MD, PhD Upper Airways Research Laboratory, Ghent University De Pintelaan 185 (1P1), B-9000 Ghent, Belgium Tel.: +32 9332 2332 Fax: +32 9332 4993 E-mail: philippe.gevaert@UGent.be *These authors contributed equally to this manuscript. Accepted for publication 20 September 2012 DOI:10.1111/all.12054 Edited by: Wytske Fokkens Abstract Background: Chronic rhinosinusitis with nasal polyps (NP) and allergic rhinitis (AR) is characterized by local Th2 inflammation and up-regulation of IgE; how- ever, IgE in NP is ‘polyclonal’ and allergen specific, whereas IgE in AR is ‘oli- goclonal’ and allergen specific. Germinal center (GC) reactions occur in AR, while only the formation of GC-like structures in NP is described. The aim of this study was to investigate the involvement of local IgE production, class switch recombination, and receptor revision in NP. Methods: We compared the levels of local IgE, germline gene transcripts, and mature Ig mRNA expression, recombination activating gene (RAG1 and RAG2), key mark- ers of Th2 inflammation, and GC reactions in NP tissue vs AR and control tissue. Nasal mucosa was immunostained for the co-expression of RAG1 and RAG2 in B cells, plasma cells, and T cells, using dual or triple immunofluorescence (IF). Results: In NP, local IgE level and key markers of local class switching are increased compared with AR and normal controls (NC). In NP, switch circle tran- scripts reveal ongoing local class switch recombination to IgE. Up to 30% of B cells, plasma cells, and T cells in nasal polyps re-express both RAG1 and RAG2, required for receptor revision. RAG1 and RAG2 mRNA concentrations are increased in NP and correlated with the magnitude of inflammation and the pres- ence of S. aureus enterotoxin (superantigen)-specific IgE in the nasal polyp mucosa. Conclusion: Our results provide the first evidence of local receptor revision and class switching to IgE, and B-cell differentiation into IgE-secreting plasma cells in NP. Chronic rhinosinusitis with nasal polyps (NP) and allergic rhinitis (AR) is characterized by Th2 inflammatory responses, eosinophilia, and IgE synthesis (1, 2). However, there are two striking differences in the mechanisms underlying these diseases. IgE synthesis in AR is skewed toward allergen- specific IgE. In contrast, IgE in NP tends to be ‘polyclonal’. Another notable difference between AR and NP is the for- mation of germinal center (GC)-like structures in polyps, which were not seen in the nasal mucosa in AR (3), even though local GC reactions, somatic hypermutation (SHM), and class switch recombination (CSR) to IgE were observed in AR (3–5). Abbreviations AID, activation-induced cytidine deaminase; AR, allergic rhinitis; BAFF, B cell–activating factor of the tumor necrosis factor (TNF) family; BLIMP, B lymphocyte–induced maturation protein; CSR, class switch recombination; ECP, eosinophil cationic protein; GC, germinal center; GLT, germline gene transcript; IF, immunofluorescence; IQR, interquartile range; NC, normal controls; NP, nasal polyps; qPCR, quantitative polymerase chain reaction; RAG, recombination activating gene product; rag, recombination activating genes; RR, receptor revision; SAE, Staphylococcus aureus enterotoxin; SHM, somatic hypermutation; TcR, T-cell receptor; V(D)J, variable (diversity) joining segment. Allergy 68 (2013) 55–63 © 2012 John Wiley & Sons A/S 55 Allergy