The lung environment controls alveolar macrophage metabolism and responsiveness during type-2 inflammation.

Fine control of macrophage activation is required to prevent inflammatory disease, particularly at barrier sites such as the lung. However, the dominant mechanisms that regulate pulmonary MFs during inflammation are currently poorly understood. Here we show that airway MFs are substantially less able to respond to the canonical type-2 cytokine IL-4, which underpins allergic disease and parasite worm infections, than lung tissue or peritoneal cavity MFs. We reveal that MF hypo-responsiveness to IL-4 is dictated by the lung environment, though independent of the host microbiota or the prominent lung extracellular matrix components surfactant protein D and mucin 5b. Rather, compared to cavity MFs,  airway MFs display severely dysregulated metabolism. Strikingly, upon removal from the lung, alveolar MFs regain IL-4 responsiveness in a process dependent upon glycolysis. Thus, we propose that impaired glycolysis within the pulmonary niche is a central determinant for regulation of MF responsiveness during type-2 inflammation. Overall design: The 13 analysed samples belong to 6 different groups, each group consisted of 2 or 3 samples. The groups consist of 3 separate macrophage populations, from either control or IL-4 complex treated mice. Each individual sample was generated from 3-5 pooled biological replicate mice.

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Svedberg FR, Brown SL, Krauss MZ, Campbell L, Sharpe C, Clausen M, Howell GJ, Clark H, Madsen J, Evans CM, Sutherland TE, Ivens AC, Thornton DJ, Grencis RK, Hussell T, Cunoosamy DM, Cook PC, MacDonald AS