In the lungs, TLR4 is also expressed at low basal levels in alveolar cells, including type I and II cells, and bronchial epithelial cells, but interestingly, TLR4 expression and sensitisation (to LPS) increase upon inflammatory insults, infiltration, or coculturing with macrophages or viral infections such as RSV [19, 65–68]. The gene discussed is TLR4; the disease is viral infectious disease.