CD4 and respiratory syncytial virus bronchiolitis: There appears to be a role of CD4+ T cells in mediating lung inflammation and pathology in RSV‐infected mice.4, 5 Immune dysregulation with an imbalance of Th1 and Th2 responses has been demonstrated in RSV‐infected mice and children.6, 7, 8 A recent study demonstrated that higher Th2 and Th17 cytokine levels in nasal wash samples obtained during acute RSV bronchiolitis were associated with recurrent wheezing at age one and 2 years.9