Although clinical symptoms of asthma patients could be induced or worsened by microbial infections [21], there are also evidence showing that TLR2 ligands could reduce allergic airway inflammation in chronic respiratory sensitization to antigens, or inhibit Th2 response to mite allergen in human through decreasing the release of Th2 cytokines such as IL-5 and IL-13 [22], [23]. This evidence concerns the gene IL5 and asthma.