“THE INNATE IMMUNE SYSTEM engages an array of germline-encoded pattern-recognition receptors (PRRs) to detect invariant microbial motifs. PRRs are expressed by cells at the front line of defense against infection, including macrophages, monocytes, dendritic cells, neutrophils, and epithelial cells, as well as cells of the adaptive immune system. PRRs include the membrane-bound Toll-like receptors (TLRs) and C-type lectins (CTLs), which scan the extracellular milieu and endosomal compartments for pathogen-associated molecular patterns (PAMPs).”
http://www.sciencedirect.com/science/article/pii/S0092867410000759