Microbiota-derived inosine programs protective CD8+ T cell responses against influenza in newborns

The immunological defects causing vulnerability to severe respiratory infections in the critical window of infancy are unresolved, reflecting a crucial gap that has hindered progress in improving clinical outcomes for this vulnerable population. We identify how the gut microbiota directs short-term functional competence and the long-term fate of pulmonary T cells through an evolutionarily conserved pathway. Here, we used rare post-mortem lung tissues from infants to overcome inherent difficulty in translational generalizability from mouse studies alone.