Exploring the mechanism found that TLR signaling played the protective function at the sensitization but not challenge phase of OVA-induced allergic asthma, and activation of TLR signaling in sensitization recruited-inflammatory monocytes significantly attenuated allergic symptoms since they up-regulated the expression of Th1-association cytokines, including IFN-γ, IL-6, and TNF-α, after stimulation with TLR agonist. This evidence concerns the gene TNF and allergic asthma.