A switch in regulatory T cells through farm exposure during immune maturation in childhood

Allergy. 2017 Apr;72(4):604-615. doi: 10.1111/all.13069. Epub 2016 Nov 17.

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+ CD25high FOXP3upper20% ). 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.

Keywords: animal-stable; asthma; farming; milk; regulatory T cells (Tregs).

Publication types

  • Multicenter Study

MeSH terms

  • Age Factors
  • Allergens / immunology
  • Animals
  • Asthma / epidemiology
  • Asthma / etiology
  • Biomarkers
  • Child
  • Child, Preschool
  • Cytokines / metabolism
  • Environmental Exposure*
  • Farms*
  • Female
  • Follow-Up Studies
  • Gene Expression
  • Humans
  • Immunity*
  • Immunoglobulin E / immunology
  • Infant
  • Infant, Newborn
  • Lymphocyte Count
  • Male
  • Phenotype
  • Population Surveillance
  • Pregnancy
  • RNA, Messenger / genetics
  • Surveys and Questionnaires
  • T-Lymphocyte Subsets / immunology*
  • T-Lymphocyte Subsets / metabolism
  • T-Lymphocytes, Regulatory / immunology*
  • T-Lymphocytes, Regulatory / metabolism

Substances

  • Allergens
  • Biomarkers
  • Cytokines
  • RNA, Messenger
  • Immunoglobulin E