Differential roles of TLR2 and TLR4 in recognition of gram-negative and gram-positive bacterial cell wall components

Toll-like receptor (TLR) 2 and TLR4 are implicated in the recognition of va rious bacterial cell wall components, such as lipopolysaccharide (LPS). To investigate in vivo roles of TLR2, we generated TLR2-deficient mice. In con trast to LPS unresponsiveness in TLR4-deficient mice, TLR2-deficient mice r esponded to LPS to the same extent as wild-type mice. TLR2-deficient macrop hages were hyporesponsive to several Gram-positive bacterial cell walls as well as Staphylococcus aureus peptidoglycan. TLR4-deficient macrophages lac ked the response to Gram-positive lipoteichoic acids. These results demonst rate that TLR2 and TLR4 recognize different bacterial cell wall components in vivo and TLR2 plays a major role in Gram-positive bacterial recognition.