Select autophagy genes maintain quiescence of tissue-resident macrophages and increase susceptibility to Listeria monocytogenes

Innate and adaptive immune responses that prime myeloid cells, such as macrophages, protect against pathogens^1,2. However, if left uncontrolled, these responses may lead to detrimental inflammation³. Macrophages, particularly those resident in tissues, must therefore remain quiescent between infections despite chronic stimulation by commensal microorganisms. The genes required for quiescence of tissue-resident macrophages are not well understood. Autophagy, an evolutionarily conserved cellular process by which cytoplasmic contents are targeted for lysosomal digestion, has homeostatic functions including maintenance of protein and organelle integrity and regulation of metabolism⁴. Recent research has shown that degradative autophagy, as well as various combinations of autophagy genes, regulate immunity and inflammation^5–12. Here, we delineate a function of the autophagy proteins Beclin 1 and FIP200—but not of other essential autophagy components ATG5, ATG16L1 or ATG7—in mediating quiescence of tissue-resident macrophages by limiting the effects of systemic interferon-γ. The perturbation of quiescence in mice that lack Beclin 1 or FIP200 in myeloid cells results in spontaneous immune activation and resistance to Listeria monocytogenes infection. While antibiotic-treated wild-type mice display diminished macrophage responses to inflammatory stimuli, this is not observed in mice that lack Beclin 1 in myeloid cells, establishing the dominance of this gene over effects of the bacterial microbiota. Thus, select autophagy genes, but not all genes essential for degradative autophagy, have a key function in maintaining immune quiescence of tissue-resident macrophages, resulting in genetically programmed susceptibility to bacterial infection.