Figure 1.

Monocytes and macrophages are a central component of the innate immune system. They are able to switch their phenotype from a homeostatic state to the proinflammatory state to eliminate pathogens and fight the inflammation. During uncomplicated inflammation, a switch from a proinflammatory to an anti-inflammatory phenotype occurs which enables the resolution of inflammation and the re-establishment of homeostasis. This enables the monocytes and macrophages to play diverse roles in the inflammatory response, both encouraging and discouraging this process. Depending on the kind of signal or pathophysiologic condition, monocytes and macrophages can undergo specific phenotypic polarization and thus acquire distinct functional phenotypes.