IFNG and viral infectious disease: Children suffering from RSV infection had high levels of Th1 cytokines.16–18 Th1 immune response is necessary for protective response against RSV.18 T cells cultured with mDCs have been shown to secrete large amounts of interferon-γ (IFN-γ).19 Interferon-γ binds to specific surface receptors on primary target cells and induces the transcription of a variety of genes that mount antiviral response.20 This antiviral immune response at an early stage of viral infection may explain our observation of increased mDCs in patients with RSV bronchiolitis at the time of admission.