Host cells express a range of receptors that act as microbial sensors. These receptors sense microorganisms and transduce signals that activate immune responses. Host cells use several strategies to recognize specific pathogen-associated molecular patterns (PAMPs). Bacterial components such as peptidoglycan, bacterial flagellin, and nucleic acid structures are examples of PAMPs. One family of cell surface pattern recognition receptors (PRRs) named as Toll-like receptors TLRs recognize PAMPs through an extracellular domain and initiate inflammatory signaling pathways through an intracellular domain. Sensing of the presence of microbes or their factors in the cytosol is mediated by NOD-like receptors (NLRs) and leads to signaling cascades that mediate the production of inflammatory cytokines, recruitment of phagocytic cells and control of the acquired immune response. Most NLRs assemble in large multiprotein complex called the inflammasome leading to the activation of caspase-1. Caspase-1 is an inflammatory caspase that is required for the activation of cytokines such as IL-1ß, IL-18 and IL-33. Caspase-1 can also induce a non-apoptotic form of cell death named pyroptosis. Dysfunction of the inflammasome can lead to exacerbated inflammation in several human conditions. On the other hand, the inflammasome response maybe absent in certain conditions, hence allowing some intracellular infections to pass unnoticed. In this issue, we will address several aspects of inflammasome activation and its role in health and disease conditions.
Host cells express a range of receptors that act as microbial sensors. These receptors sense microorganisms and transduce signals that activate immune responses. Host cells use several strategies to recognize specific pathogen-associated molecular patterns (PAMPs). Bacterial components such as peptidoglycan, bacterial flagellin, and nucleic acid structures are examples of PAMPs. One family of cell surface pattern recognition receptors (PRRs) named as Toll-like receptors TLRs recognize PAMPs through an extracellular domain and initiate inflammatory signaling pathways through an intracellular domain. Sensing of the presence of microbes or their factors in the cytosol is mediated by NOD-like receptors (NLRs) and leads to signaling cascades that mediate the production of inflammatory cytokines, recruitment of phagocytic cells and control of the acquired immune response. Most NLRs assemble in large multiprotein complex called the inflammasome leading to the activation of caspase-1. Caspase-1 is an inflammatory caspase that is required for the activation of cytokines such as IL-1ß, IL-18 and IL-33. Caspase-1 can also induce a non-apoptotic form of cell death named pyroptosis. Dysfunction of the inflammasome can lead to exacerbated inflammation in several human conditions. On the other hand, the inflammasome response maybe absent in certain conditions, hence allowing some intracellular infections to pass unnoticed. In this issue, we will address several aspects of inflammasome activation and its role in health and disease conditions.