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TNF? is an important inflammatory cytokine that triggers responses in many diffe

ID: 132183 • Letter: T

Question

TNF? is an important inflammatory cytokine that triggers responses in many different cells. Drugs that inhibit TNF? signaling are used to treat some autoimmune diseases. Which of the following are components of a positive feedback loop in inflammation? (select two answers)

*IL-8 secretion by endothelial cells, induced by TNF?

*phagocytosis of bacteria by macrophages

*phagocytosis of bacteria by neutrophils

*secretion of TNF? by macrophages

*secretion of TNF? by neutrophils

...secrete IL-8 which binds to... phagocytose issue neutrophils bind to.. MicrobesMacrophages Circulating neutrophils ...phagocytose... secrete TNFa, which binds to.. Endothelial cells ...secrete 1L-8 which binds to...

Explanation / Answer

Ans.

IL-8 secretion by endothelial cells, induced by TNF and secretion of TNF by neutrophils are components of a positive feedback loop in inflammation.

IL-8 secreted by endothelial cells binds to circulating neutrophils which migrate into tissue and become tissue neutrophils. the TNF secreted by those tissue neutrophils in turn binds to the endolthelial cells and stimulates secretion of IL-8 thus completing the positive feedback loop.