Quantitative and functional impairment of pulmonary CD4+CD25hi regulatory T cells in pediatric asthma

Background: Asthma is characterized by a T(H)2 immune response. CD4(+)CD251(hi) regulatory T cells (Tregs) have been proposed to prevent allergic diseases through suppression of T(H)2 responses. Objective: We sought to investigate the role of CD4(+)CD25(hi). T cells in children with asthma. Methods: CD4(+)CD25(hi) Tregs and forkhead/winged-helix transcription factor FOXP3 mRNA levels were quantified in peripheral blood and bronchoalveolar lavage fluid (BALF) of 18 children with asthma, 10 children with chronic cough, and 13 control subjects without lung diseases. CD4(+)CD25(hi) T cells were isolated from peripheral blood and BALF of asthmatic patients and control subjects, and their capacity to suppress proliferation and cytokine/chemokine production of auotologous responder T cells was analyzed. Results: CD4(+)CD25(hi) T cells were decreased in BALF of asthmatic children compared with values in children with cough or control subjects. In children with asthma, inhaled corticosteroid treatment was associated with increased percentages of CD4(+)CD25(hi) T cells in peripheral blood and BALE Isolated BALF and peripheral blood CD4+CD25 hi T cells from nonasthmatic subjects suppressed proliferation and cytokine/chemokine production by CD4(+)CD25(-) responder T cells. BALF CD4(+)CD25(hi) T cells from asthmatic subjects failed to suppress proliferation and production of T(H)2 associated cytokines and chemokines by CD4(+)CD25(-)responder T cells, which was restored after use of inhaled corticosteroids. Conclusion: These findings provide the first evidence that pulmonary CD4(+)CD25(hi) Tregs are impaired in pediatric asthma. Clinical implications: Pulmonary Tregs might represent a therapeutic target in pediatric asthma.