TLR4 and pneumonia: In pneumococcal meningitis, multiple microbial pattern recognition receptors including Toll-like family of the receptors (TLRs) were expressed to perceive bacterial pathogens and to initiate potentially damaging CNS inflammation Klein et al. [14] have recently demonstrated that TLR2 and TLR4 expressed on radioresistant and transplanted BM-derived cells were major cellular sensors of invading S. pneumoniae inducing inflammatory responses in murine S. pneumoniae meningitis.