Figure 2.

Macrophage polarization and chronic inflammation. A variety of stimuli are known to induce either M1-like pro-inflammatory or M2-like anti-inflammatory polarization. These polarization states represent the extremes of a spectrum of activation profiles, dependent on nature of the stimulus and microenvironmental factors. Self-resolving inflammation is transient and considered a necessary physiological response in maintaining homeostasis and host-defense. If polarization is persistent, downstream signaling from macrophages also leads to lymphocyte polarization. Sustained dysregulated macrophage activation and lymphocytic polarization are important parts of a number of pathologies.