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(+) CD25(high) FOXP3(upper20%) ). 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-gamma (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.
- Schroder, P. C.
- Illi, S.
- Casaca, V. I.
- Lluis, A.
- Bock, A.
- Roduit, C.
- Depner, M.
- Frei, R.
- Genuneit, J.
- Pfefferle, P. I.
- Roponen, M.
- Weber, J.
- Braun-Fahrlander, C.
- Riedler, J.
- Dalphin, J. C.
- Pekkanen, J.
- Lauener, R.
- von Mutius, E.
- Schaub, B.
- Pasture study group
Keywords
- Age Factors
- Allergens/immunology
- Animals
- Asthma/epidemiology/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/metabolism
- T-Lymphocytes, Regulatory/*immunology/metabolism
- animal-stable
- asthma
- farming
- milk
- regulatory T cells (Tregs)