Immunity 48, 992–1005 (2018)

Dietary fiber provides protection against chronic and allergic airway inflammation. In Immunity, Marsland and colleagues show that a high-fiber diet (HFiD) also ameliorates the lung pathology of influenza virus–infected mice. Mice fed the HFiD, which increases the production of short-chain fatty acids by the intestinal microbiota, or mice given direct supplementation with the short-chain fatty acid butyrate, have greater differentiation of Ly6C– monocytes and tissue repair–prone interstitial and alveolar macrophages, less production of the neutrophil chemoattractant CXCL1, and less infiltration of neutrophils in the lungs than that of mice fed a low-fiber diet. In addition, the HFiD and butyrate directly enhance the metabolism of CD8+ T cells, which results in greater population expansion of virus-specific cells and enhanced cytotoxic capacity. The effects are mediated through the G protein–coupled receptor GPR41.