In particular, whereas in WT mice S. pneumoniae D39 and PLN induced a similar early TNF-α response in the lungs, the pulmonary levels of this crucially protective cytokine in the early response to pneumococcal pneumonia (van der Poll et al., 1997; Rijneveld et al., 2001) were more than 4-fold lower in TLR2 KO mice after infection with S. pneumoniae PLN versus 2-fold lower after inoculation with S. pneumoniae D39. Here, TLR2 is linked to pneumococcal pneumonia.