Fig. 2.

Macrophage responses to endogenous and exogenous regulators. Left: stimulated macrophages produce and release ATP. The macrophage ectoenzymes CD39 and CD73 rapidly convert ATP to adenosine,⁴⁷ which signals through high-affinity receptors for adenosine to switch off the production of inflammatory mediators and to induce the production of growth-associated and angiogenic factors. Stimulated human macrophages also upregulate the synthesis of PGE₂ and the receptors for PGE₂, causing them to become exquisitely sensitive to the regulatory effects of PGE₂. Macrophages also catabolize lipids into lipoxins and resolvins to dampen inflammatory responses. Right: neighboring cells, including fibroblasts, endothelial cells, neutrophils, and platelets, can also be a source of these regulatory molecules. These neighboring cells can also be stimulated to produce “enhancer” molecules that amplify the initial activation response. This image was prepared using Medical ART (https://smart.servier.com/)