TLR2 and gram-positive bacterial infections: In the early course of infection, as the first line of defense against pathogens, macrophages can recognize and respond rapidly to invading microbes by the expression of pattern recognition receptors (PRRs) such as toll-like receptor 2 (TLR2) or TLR4 and nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs), which show increased susceptibility to gram-negative and gram-positive bacterial infections, respectively (Elson et al., 2007).