TLR4 and susceptibility to pneumonia measurement: The roles of Toll-like receptor (TLR) 2 and TLR4, well known NTHi recognizing receptor in lung epithelial cell and gram-negative bacteria receptor, respectively, on the NTHi-induced COX-2 expression were investigated in the HEK293 cells overexpressing TLR2 and TLR4 in vitro and in the mouse model of NTHi-induced pneumonia by using TLR2 and TLR4 knock-out mice in vivo.