Macrophage FABP4 is required for neutrophil recruitment and bacterial clearance in Pseudomonas aeruginosa pneumonia

What is it about?

Fatty Acid Binding Protein 4 is a protein that is found in macrophages. It has been shown to promote inflammatory activity of macrophages in atherosclerosis. FABP4 is also present in macrophages in the lung, where its biological function remains to be elucidated. Since macrophages are the first line of defense against many microbes, we investigated whether FABP4 protein in macrophages could contribute to the body's natural defense system to fight bacterial pneumonia caused by Pseudomonas aeruginosa, a common cause of pneumonia that primarily affects patients with weakened immune systems. Our results demonstrate that macrophage-derived FABP4 plays a protective role indirectly by recruiting other inflammatory cells, primarily neutrophils, to the lung to clear the bacteria. This is accomplished by increased production of a molecule in macrophages that sends chemical cues to the neutrophils to attract them to the site of infection in the lung. Thus, our findings imply FABP4 as an important contributor to the natural defense system of the lung against bacterial pathogens.

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