Association between CD4+CD25high T cells and atopy in children

BackgroundThere is evidence that CD4+CD25high T-regulatory cells are important for establishing tolerance to allergens, but information in children is limited.ObjectiveTo test the hypothesis that greater numbers and function of CD4+CD25high T cells are associated with a reduced risk of childhood allergies and wheezing.MethodsA cohort of 151 six-year-old children from atopic families was analyzed for peripheral blood CD4+CD25high and CD4+CD25int T cells by flow cytometry and for clinical and immunologic correlates of atopy. The associations between these variables were assessed by regression analysis.ResultsFactors positively associated with % CD4+CD25high/CD4 T cells were male sex, number of positive allergen-specific IgE tests, total IgE, season, and 1-month average total pollen count preceding blood draw. The percentage of CD4+CD25high/total CD4 T cells did not correlate with induced cytokine production, and correlated negatively with suppressive capacity of CD4+CD25+ T cells (r = –0.45; P = .034). The percentage of CD4+CD25int/CD4 T cells was 54% higher in pollen-sensitized children compared with nonsensitized children in spring (P = .023 for interaction), and correlated positively with IL-5, IL-10, and IL-13 (P ≤ .001 for all).ConclusionOur findings suggest that blood CD4+CD25high cells are a mixture of activated and regulatory T cells, and that these cells could be seasonally regulated by environmental factors such as pollen exposure.Clinical implicationsSeasonal increases in CD4CD25high expression in children with allergy may represent systemic immune activation caused by pollen exposures.