CD4 and respiratory syncytial virus bronchiolitis: In the upper airways, a decrease in IL‐10 potentiates an increase in the TNF‐α response which controls the viral infection.31 As diminished TNF‐α observed in recurrent wheezers after both stimulation conditions from peripheral blood‐derived CD4+ T cells and the significant differences in the levels of TNF‐α among four wheezing categories, evidence suggests that (a) CD4+ T cells may be impaired in their production of TNF‐α during RSV infection and (b) TNF‐α may play roles in the pathogenesis of airway inflammation and subsequent wheezing following severe RSV bronchiolitis in children.