The PRR danger signal receptors are divided into two major types membrane-associated and cytosolic, based on cellular localization (Bryant and Fitzgerald, 2009) (Fig 1). Membrane-associated PRRs include TLRs and C-type lectin receptors (CLR), and cytosolic PRRs include nucleotide-binding oligomerization domain (NOD)-like receptors (NLR), retinoic acid-inducible gene (RIG)-like RNA helicases (RIR), and DNA sensor (absent in melanoma 2: AIM2 etc.). Activation of TLRs leads to increased transcription of pro-IL- 1β, which is subsequently processed by activation of the NLRP3 inflammasome complex (also referred to as cryopyrin or NALP3). NLRP3 has a tripartite structure, consisting of a C-terminal leucine- rich repeat domain (LRR), a central nucleotide-binding oligomerization (NACHT) and N-terminal protein–protein interaction domain, and a Pyrin domain (PYD) (Bryant and Fitzgerald, 2009) (Fig 2). Of all the NLRs, NLRP3 is activated by the most diverse array of danger signals. In addition to PAMPs, NLRP3 also recognizes molecules with damage-associated molecular patterns (DAMPs).
