Mixed Th1/Th2-type immune responses (including eosinophils, neutrophils, and both IL-13- and IFN-γ-producing CD4+ T cells) are also a feature of vaccine-enhanced RSV disease in mice and of human bronchiolitis (44, –, 46), indicating that dysregulation is the hallmark of RSV disease. The gene discussed is CD4; the disease is bronchiolitis.