Induction of autonomous memory alveolar macrophages requires T-cell help and is critical to trained immunity

Innate immune memory is a new important area of research. However, innate immune memory at the major mucosal sites remains poorly understood. Here we show that respiratory viral infection induces long-lasting memory alveolar macrophages (AM). Memory AM are programed to express high MHC II, carry a defense-ready gene signature, and produce, upon re-stimulation, neutrophil chemokines. Using a multitude of approaches, we reveal that the priming, but not maintenance, of memory AM requires the help from effector CD8 T cells. T cells jump-start this process in AM via IFN- production. We further find that formation/maintenance of memory AM are independent of monocytes or bone marrow progenitors. Finally, we demonstrate that memory AM are poised for robust trained immunity against bacterial infection in the lung via rapid induction of chemokines and neutrophilia. Our study thus establishes a new paradigm of immunological memory formation whereby adaptive T-lymphocytes render innate memory of mucosal-associated macrophages.

6

Yao Y, Jeyanathan M, Haddadi S, Barra NG, Vaseghi-Shanjani M, Damjanovic D, Lai R, Afkhami S, Chen Y, Dvorkin-Gheva A, Robbins CS, Schertzer JD, Xing Z