title: A switch in regulatory T cells through farm exposure during immune maturation in childhood.
abstract: BACKGROUND
  Farm exposure protects against development of allergies early in life. At 4.5 years, protection against asthma by farm-milk exposure was partially mediated by regulatory T cells (Tregs). The aim of this study was to investigate the critical time window of the 'asthma-protective' farm effect via Tregs during childhood immune maturation.
  
  
  METHODS
  Tregs were assessed longitudinally at 4.5 and 6 years in 111 children (56 farm and 55 reference children) from the PASTURE/EFRAIM birth cohort (flow cytometry). Peripheral blood mononuclear cells were cultured unstimulated (U), with phorbol 12-myristate 13-acetate/ionomycin (PI) or lipopolysaccharide (LPS), and stained for Tregs (CD4+CD25highFOXP3upper20%). mRNA expression of Treg/Th1/Th2/Th17-associated cell markers was measured ex vivo. Suppressive capacity of Tregs on effector cells and cytokines was assessed. Detailed questionnaires assessing farm exposures and clinical phenotypes from birth until age 6 years were answered by the parents.
  
  
  RESULTS
  Treg percentage before and after stimulation and FOXP3mRNA expression ex vivo decreased from age 4.5 to 6 years (P(U,LPS) < 0.001; P(PI) = 0.051; P(FOXP3) < 0.001). High vs low farm-milk and animal-stable exposure was associated with decreased LPS-stimulated Treg percentage at age 6 years (P(LPS) = 0.045). Elevated LPS-stimulated-Treg percentage at age 6 was associated with increased risk of asthma (aOR = 11.29, CI: 0.96-132.28, P = 0.053). Tregs from asthmatics vs nonasthmatics suppressed IFN-γ (P = 0.015) and IL-9 (P = 0.023) less efficiently. mRNA expression of Th1/Th2/Th17-associated cell markers decreased between 4.5 and 6 years (P < 0.001).
  
  
  CONCLUSIONS
  Tregs at the age of 6 years were decreased with farm exposure and increased within asthmatics, opposite to age 4.5 years. This immunological switch defines a critical 'time window' for Treg-mediated asthma protection via environmental exposure before age 6 years.
authors.affiliation: LMU Munich, University Children's Hospital, Munich, Germany.
authors.forename: P C
authors.initials: PC
authors.lastname: Schröder
authors.affiliation: LMU Munich, University Children's Hospital, Munich, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Illi
authors.affiliation: LMU Munich, University Children's Hospital, Munich, Germany.
authors.forename: V I
authors.initials: VI
authors.lastname: Casaca
authors.affiliation: National Jewish Health, Denver, CO, USA.
authors.forename: A
authors.initials: A
authors.lastname: Lluis
authors.affiliation: LMU Munich, University Children's Hospital, Munich, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Böck
authors.affiliation: Children's Hospital, University of Zürich, Zürich, Switzerland.|Christine Kühne - Center for Allergy Research and Education (CK-CARE), Davos, Switzerland.
authors.forename: C
authors.initials: C
authors.lastname: Roduit
authors.affiliation: LMU Munich, University Children's Hospital, Munich, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Depner
authors.affiliation: Christine Kühne - Center for Allergy Research and Education (CK-CARE), Davos, Switzerland.|Swiss Institute of Allergy and Asthma Research (SIAF), University of Zurich, Davos, Switzerland.
authors.forename: R
authors.initials: R
authors.lastname: Frei
authors.affiliation: Institute of Epidemiology and Medical Biometry, Ulm University, Ulm, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Genuneit
authors.affiliation: Comprehensive Biomaterial Bank Marburg CBBM, Fachbereich Medizin der Philipps Universität Marburg, Zentrum für Tumor und Immunbiologie ZTI, Marburg, Germany.|Member of the German Centre for Lung Research (DZL), Munich, Germany.
authors.forename: P I
authors.initials: PI
authors.lastname: Pfefferle
authors.affiliation: Department of Environmental Science, Inhalation Toxicology Laboratory, University of Eastern Finland, Kuopio, Finland.
authors.forename: M
authors.initials: M
authors.lastname: Roponen
authors.affiliation: LMU Munich, University Children's Hospital, Munich, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Weber
authors.affiliation: Swiss Tropical and Public Health Institute, Basel, Switzerland.|University of Basel, Basel, Switzerland.
authors.forename: C
authors.initials: C
authors.lastname: Braun-Fahrländer
authors.affiliation: Children's Hospital Schwarzach, Schwarzach, Austria.|Teaching Hospital of Paracelsus Medical Private University Salzburg, Salzburg, Austria.
authors.forename: J
authors.initials: J
authors.lastname: Riedler
authors.affiliation: Department of Respiratory Disease, University Hospital, University of Besançon, Besançon, France.
authors.forename: J C
authors.initials: JC
authors.lastname: Dalphin
authors.affiliation: Department of Health Protection, National Institute for Health and Welfare, Kuopio, Finland.|Department of Public Health, University of Helsinki, Helsinki, Finland.
authors.forename: J
authors.initials: J
authors.lastname: Pekkanen
authors.affiliation: Christine Kühne - Center for Allergy Research and Education (CK-CARE), Davos, Switzerland.|Children's Hospital of Eastern Switzerland, St. Gallen, Switzerland.
authors.forename: R
authors.initials: R
authors.lastname: Lauener
authors.affiliation: LMU Munich, University Children's Hospital, Munich, Germany.|Comprehensive Pneumology Centre Munich (CPC-M), German Centre for Lung Research (DZL), Munich, Germany.
authors.forename: E
authors.initials: E
authors.lastname: von Mutius
authors.affiliation: LMU Munich, University Children's Hospital, Munich, Germany.|Comprehensive Pneumology Centre Munich (CPC-M), German Centre for Lung Research (DZL), Munich, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Schaub
mesh_terms: D000367:Age Factors; D000485:Allergens / Q000276:immunology; D000818:Animals; D001249:Asthma / Q000453:epidemiology / Q000209:etiology; D015415:Biomarkers; D002648:Child; D002675:Child, Preschool; D016207:Cytokines / Q000378:metabolism; D004781:Environmental Exposure; D000072480:Farms; D005260:Female; D005500:Follow-Up Studies; D015870:Gene Expression; D006801:Humans; D007109:Immunity; D007073:Immunoglobulin E / Q000276:immunology; D007223:Infant; D007231:Infant, Newborn; D018655:Lymphocyte Count; D008297:Male; D010641:Phenotype; D011159:Population Surveillance; D011247:Pregnancy; D012333:RNA, Messenger / Q000235:genetics; D011795:Surveys and Questionnaires; D016176:T-Lymphocyte Subsets / Q000276:immunology* / Q000378:metabolism; D050378:T-Lymphocytes, Regulatory / Q000276:immunology* / Q000378:metabolism
chemical_list: D000485:Allergens; D015415:Biomarkers; D016207:Cytokines; D012333:RNA, Messenger; D007073:Immunoglobulin E
keywords: animal-stable; asthma; farming; milk; regulatory T cells (Tregs)