High proportions of FOXP3(+)CD25(high) T cells in neonates are positively associated with allergic sensitization later in childhood

BACKGROUND: The role of FOXP3(+) regulatory T cells in the prevention against sensitization and allergy development is controversial. OBJECTIVE: We followed 65 newborn Swedish children from farming and non-farming families from birth to 3 years of age and investigated the relation between CD4(+) T cell subsets in blood samples and development of sensitization and allergic disease. METHODS: The proportions of FOXP3(+)CD25(high), CTLA-4(+)CD25(+), CD45RO(+), HLA-DR(+), CCR4(+) or α4β7(+) within the CD4(+) T cell population were examined by flow cytometry of blood samples at several time-points. Mononuclear cells were isolated from blood and stimulated with birch allergen, ovalbumin or the mitogen PHA, and the levels of IL-1β, IL-6, TNF, IFN-γ, IL-5 and IL-13 were measured. A clinical evaluation regarding the presence of allergen-specific IgE and allergy was performed at 18 and 36 months of age. RESULTS: Multivariate discriminant analysis revealed that children who were sensitized at 18 or 36 months of age had higher proportions of FOXP3(+)CD25(high) T cells at birth and at 3 days of life than children who remained non-sensitized, whereas allergy was unrelated to the neonatal proportions of these cells. The proportions of CTLA-4(+)CD25(+) T cells were unrelated to both sensitization and allergy. The association between higher proportions of FOXP3(+)CD25(high) T cells and sensitization persisted after exclusion of farmer's children. Finally, a farming environment was associated with lower proportions of FOXP3(+)CD25(high) T cells in early infancy and to a more prominent T cell memory conversion and cytokine production. CONCLUSION & CLINICAL RELEVANCE: Our results indicate that high proportions of FOXP3(+)CD25(high) T cells in neonates are not protective against later sensitization or development of allergy.