DAMPs, PAMPs, and PRR’s Quiz
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Microorganisms trigger the innate immune response through PAMPs. PAMPs for Gram-negative bacteria include LPS and flagellin.
The alternative complement system can be activated directly by microorganisms and the C3b that binds to the surface of a microorganism acts as an opsonin and actives the MAC complex. Complement components are available in acute settings, whereas opsonic antibody will require time to be produced.
IgG and C3b function as opsonins. Opsonins attach to the outer surface of pathogens and increase the speed of engulfment by phagocytosis. This is especially important for encapsulated bacteria which are otherwise too slippery for phagocytes to bind.
Immune complexes activate the classical complement pathway. C3a and C5a act as anaphylatoxins that recruit inflammatory cells. It is the inflammation that causes most of the tissue damage. SLE is a model immune complex disease.
PAMPs are molecules produced by microorganisms that are identified by pattern recognition receptors (PRRs) of immune cells in the tissue. The best known PRRs are the Toll-like receptors (TLRs), especially TLR-4 for LPS and TLR-5 for flagellin. Activation of TLRs activates the transcription factor NF-kB with the release of cytokines. Key cytokines include IL-1 (fever), TNF-alpha (fatigue, malaise) and IL-6 (acute phase response proteins).
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