TLR4 and infection: Whereas during infection of TLR2 KO mice with WT pneumococci, the interaction between TLR4 and pneumolysin apparently is sufficient to maintain an adequate immune response, during infection of TLR2 KO mice with pneumolysin-deficient S. pneumoniae, the absence of the interaction between pneumococcal TLR2 ligands, such as lipoteichoic acid and peptidoglycan, cannot be compensated for by the TLR4 pneumolysin-mediated immune response.