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How do monocytes become macrophages during inflammation?

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Pathways of complement activation — inflammation The main function of complement proteins is to aid in the destruction of pathogens by piercing their outer membranes (cell lysis) or by making them more attractive to phagocytic cells such as macrophages (a process known as opsonization). Some complement components also promote inflammation by stimulating cells to release histamine and by attracting phagocytic cells to the site of infection.

Monocytes become macrophages through a process of differentiation that occurs after they migrate from the bloodstream into body tissues.12

During inflammation, this transformation is guided by the local environment, specifically through the influence of cytokines and growth factors. The presence of colony-stimulating factors, particularly macrophage colony-stimulating factor (M-CSF), triggers the monocytes to develop into macrophages.1

While neutrophils are typically the first responders to an injury, monocytes often arrive at the site of inflammation roughly 24 to 48 hours later. Once they have differentiated, these macrophages play essential roles in engulfing pathogens, clearing cellular debris, and regulating the inflammatory response. Depending on the specific environmental cues they receive, they may further polarize into pro-inflammatory (M1) or anti-inflammatory (M2) phenotypes.312