TLR4 and asthma: Whereas the TLR1/TLR2 specific ligand Pam3CSK4 and high concentrations of the TLR4 ligand E. coli LPS have beneficial effects in asthma animal models [12-14], low-dose LPS and the TLR2 ligand peptidoglycan bias the immune response toward a Th2 phenotype and lead to aggravation of experimental allergic asthma [12,15].