TLR4 and influenza: Pathogen associated molecular patterns (PAMPs)(e.g., LPS, muramyl dipeptides, influenza) acting through their respective pattern recognition receptors (PRRs) [e.g., toll-like receptor 4 (TLR4) for LPS), as well as extracellular adenosine tri-phosphate (ATP) release by means of purine type 2 receptors (P2Rs), activate inflammasomes [227].