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Why do neutrophils gather at sites of acute inflammation?

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Tuberculosis — disease A doctor examining chest X-rays of patients infected with tuberculosis, which remains one of the world's deadliest diseases.

Neutrophils gather at sites of acute inflammation primarily to perform their role as phagocytes, where they ingest and destroy bacteria and clear cellular debris caused by tissue injury.12

Their migration to these sites is driven by a process called chemotaxis. When tissue is damaged, it releases chemical substances known as chemotactic factors that diffuse into the surrounding area, creating a concentration gradient. Neutrophils detect this gradient and actively move along it, exiting blood vessels to reach the site of injury.13

Once they arrive, neutrophils use potent enzymes and reactive oxygen species, such as hydrogen peroxide, to neutralize pathogens. Because they are short-lived and highly active, they often die in large numbers after completing their mission, contributing to the formation of pus at the site of inflammation. To ensure a rapid response, the bone marrow maintains a large reserve of neutrophils that can be mobilized immediately upon receiving these chemical signals.321