TLR4 and viral infectious disease: Stimulation of toll-like receptor 4 (TLR4) by lipopolysaccharide (LPS) or of TLR3 by poly (I:C) to mimic a bacterial or a viral infection respectively, leads to a classical macrophage activation state (M1) with the production of cytokines (such as tumor necrosis factor-α (TNF-α) and IL-6) and a particular subset of CC and CXC chemokines.