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NBME 21 Answers

nbme21/Block 1/Question#46

A 66-year-old man is brought to the emergency ...

Lipopolysaccharide stimulation of toll-like receptor

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submitted by meningitis(119),

LPS found in outer membrane of gram ⊝ bacteria (both cocci and rods). Composed of O antigen + core polysaccharide + lipid A (the toxic component).

Activates Macrophages and induces TNFalpha release -> Hypotension and fever.

Pg 133 Endotoxin.

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submitted by nala_ula(32),

Toll like receptors are pattern recognition receptors (on innate immunity cells like macrophages) that recognize pathogen associated molecular patterns (PAMPs) and lead to activation of NF-kB. One example of a PAMP is LPS (gram negative bacteria). This leads to secretion of IL-1, IL-6 (cause fever), TNF-a (causes fever and hypotension), Nitric Oxide (causes hypotension).

Complement activation itself leads to hypotension via C3a, as well.

All this can be found on page 133 on FA, as @meningitis pointed out, and page 99 of FA 2019.