Mukuherjee et al. [15] found that the Notch ligand Dll4 promoted T-cell differentiation through increased expression of IL-17 and RORγ T. Schaller et al. [10] also found that Dll4 expression on bone marrow-derived dendritic cells (DCs) increased significantly after infection of mice with respiratory syncytial virus, accompanied by increased secretion of Th2 cytokines and reduced production of INF-γ. The gene discussed is DLL4; the disease is infection.