The inflammasomes: platforms of innate immunity

Human beings are constantly exposed to pathogens. The innate immune system is the first line of defense against microbes. It has evolved to recognize conserved microbial motifs (PAMP or pathogen-associated molecular patterns) thanks to a limited array of receptors termed pattern recognition receptors (PRR). Upon activation, most PRR trigger a transcriptional response leading to neosynthesis of hundreds of genes. In contrast, engagement of various PRR in the recently identified inflammasome complexes lead to activation of a cysteine protease, caspase-1. This inflammatory caspase has a dual activity : it triggers the release of very potent proinflammatory cytokines IL-1 beta and IL-18 and, an hyperinflammatory cell death termed pyroptosis. In this review, we describe the inflammasome receptors and their ligands, the molecular mechanisms leading to the assembly of this innate immune platform and the role of the inflammasome during viral and bacterial infections.