Pathogen recognition by innate immunity

Abstract

The innate immune system provides the first line of host defense against invading microorganisms. The innate immune responses are initiated by the pattern recognition receptors (PRRs), which detect conserved structures found in microorganisms. Among them, Toll-like receptors (TLRs), which locate on the cell surface or in the endosomal compartments are capable of sensing organisms ranging from bacteria to fungi, protozoa and viruses and play a major role in innate immunity. On the other hand, cytoplasmic PRRs such as NOD-like receptors (NLRs) and RIG-like receptors (RLRs) detect bacteria and viruses that have invaded cytosols. This review summarizes the function and signaling pathways of PRRs.