title: IL-9 is a key component of memory TH cell peanut-specific responses from children with peanut allergy.
abstract: BACKGROUND
  Differentiation between patients with peanut allergy (PA) and those with peanut sensitization (PS) who tolerate peanut but have peanut-specific IgE, positive skin prick test responses, or both represents a significant diagnostic difficulty. Previously, gene expression microarrays were successfully used to identify biomarkers and explore immune responses during PA immunotherapy.
  
  
  OBJECTIVE
  We aimed to characterize peanut-specific responses from patients with PA, subjects with PS, and atopic children without peanut allergy (NA children).
  
  
  METHODS
  A preliminary exploratory microarray investigation of gene expression in peanut-activated memory TH subsets from 3 children with PA and 3 NA children identified potential PA diagnostic biomarkers. Microarray findings were confirmed by using real-time quantitative PCR in 30 subjects (12 children with PA, 12 children with PS, and 6 NA children). Flow cytometry was used to identify the TH subsets involved.
  
  
  RESULTS
  Among 12,257 differentially expressed genes, IL9 showed the greatest difference between children with PA and NA children (45.59-fold change, P < .001), followed by IL5 and then IL13. Notably, IL9 allowed the most accurate classification of children with PA and NA children by using a machine-learning approach with recursive feature elimination and the random forest algorithm. Skin- and gut-homing TH cells from donors with PA expressed similar TH2- and TH9-associated genes. Real-time quantitative PCR confirmed that IL9 was the highest differentially expressed gene between children with PA and NA children (23.3-fold change, P < .01) and children with PS (18.5-fold change, P < .05). Intracellular cytokine staining showed that IL-9 and the TH2-specific cytokine IL-5 are produced by distinct TH populations.
  
  
  CONCLUSIONS
  In this study IL9 best differentiated between children with PA and children with PS (and atopic NA children). Mutually exclusive production of IL-9 and the TH2-specific cytokine IL-5 suggests that the IL-9-producing cells belong to the recently described TH9 subset.
authors.affiliation: Division of Asthma, Allergy and Lung Biology, King's College London, and Guys' Hospital, London, United Kingdom; MRC & Asthma UK Centre in Allergic Mechanisms of Asthma, King's College London, and Guys' Hospital, London, United Kingdom.
authors.forename: Helen A
authors.initials: HA
authors.lastname: Brough
authors.affiliation: Division of Asthma, Allergy and Lung Biology, King's College London, and Guys' Hospital, London, United Kingdom; MRC & Asthma UK Centre in Allergic Mechanisms of Asthma, King's College London, and Guys' Hospital, London, United Kingdom; Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom.
authors.forename: David J
authors.initials: DJ
authors.lastname: Cousins
authors.affiliation: Faculty of Computer Science, University of Iasi, Iasi, Romania.
authors.forename: Alina
authors.initials: A
authors.lastname: Munteanu
authors.affiliation: Genomics Centre, King's College London, London, United Kingdom.
authors.forename: Yuen Fei
authors.initials: YF
authors.lastname: Wong
authors.affiliation: Division of Asthma, Allergy and Lung Biology, King's College London, and Guys' Hospital, London, United Kingdom; MRC & Asthma UK Centre in Allergic Mechanisms of Asthma, King's College London, and Guys' Hospital, London, United Kingdom.
authors.forename: Asha
authors.initials: A
authors.lastname: Sudra
authors.affiliation: Division of Asthma, Allergy and Lung Biology, King's College London, and Guys' Hospital, London, United Kingdom; MRC & Asthma UK Centre in Allergic Mechanisms of Asthma, King's College London, and Guys' Hospital, London, United Kingdom.
authors.forename: Kerry
authors.initials: K
authors.lastname: Makinson
authors.affiliation: Division of Asthma, Allergy and Lung Biology, King's College London, and Guys' Hospital, London, United Kingdom; MRC & Asthma UK Centre in Allergic Mechanisms of Asthma, King's College London, and Guys' Hospital, London, United Kingdom.
authors.forename: Alick C
authors.initials: AC
authors.lastname: Stephens
authors.affiliation: Genomics Centre, King's College London, London, United Kingdom.
authors.forename: Matthew
authors.initials: M
authors.lastname: Arno
authors.affiliation: Faculty of Computer Science, University of Iasi, Iasi, Romania.
authors.forename: Liviu
authors.initials: L
authors.lastname: Ciortuz
authors.affiliation: Division of Asthma, Allergy and Lung Biology, King's College London, and Guys' Hospital, London, United Kingdom; MRC & Asthma UK Centre in Allergic Mechanisms of Asthma, King's College London, and Guys' Hospital, London, United Kingdom.
authors.forename: Gideon
authors.initials: G
authors.lastname: Lack
authors.affiliation: Division of Asthma, Allergy and Lung Biology, King's College London, and Guys' Hospital, London, United Kingdom; MRC & Asthma UK Centre in Allergic Mechanisms of Asthma, King's College London, and Guys' Hospital, London, United Kingdom. Electronic address: victor.turcanu@kcl.ac.uk.
authors.forename: Victor
authors.initials: V
authors.lastname: Turcanu
mesh_terms: D000293:Adolescent; D010367:Arachis / Q000009:adverse effects / Q000276:immunology; D002648:Child; D002675:Child, Preschool; D016207:Cytokines / Q000235:genetics* / Q000276:immunology; D004311:Double-Blind Method; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D007073:Immunoglobulin E / Q000276:immunology; D007156:Immunologic Memory; D007223:Infant; D007963:Leukocytes, Mononuclear / Q000276:immunology; D008297:Male; D020411:Oligonucleotide Array Sequence Analysis; D021183:Peanut Hypersensitivity / Q000175:diagnosis / Q000276:immunology*; D012867:Skin / Q000166:cytology; D012882:Skin Tests; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*
chemical_list: D016207:Cytokines; D007073:Immunoglobulin E
keywords: IL-13; IL-5; IL-9; Peanut allergy; T(H)2; T(H)9; gene expression; microarray; peanut sensitization; real-time quantitative PCR