Unveiling the roles of autophagy in innate and adaptive immunity

Key Points Autophagy has a role in degrading intracellular bacteria, parasites and viruses. Intracellular pathogens have strategies to subvert or evade the autophagy pathway. Autophagy has a role in innate immune signalling by delivering viral nucleic acids to endosomal Toll-like receptors. Autophagy is active in antigen-presenting cells and is involved in MHC class II presentation of certain endogenous antigens. Immune signalling molecules that are important in the control of viruses, parasites and intracellular bacteria activate autophagy. Autophagy is involved in regulating T-cell homeostasis. Autophagy genes are strongly linked to susceptibility to Crohn's disease, a form of inflammatory bowel disease. Autophagy — a cellular process for recycling, remodelling or disposing of unwanted cytoplasmic constituents — is emerging as an important pathway in innate and adaptive immunity. This Review describes its role in pathogen defence, antigen processing and presentation, T-cell homeostasis and disease. Cells digest portions of their interiors in a process known as autophagy to recycle nutrients, remodel and dispose of unwanted cytoplasmic constituents. This ancient pathway, conserved from yeast to humans, is now emerging as a central player in the immunological control of bacterial, parasitic and viral infections. The process of autophagy may degrade intracellular pathogens, deliver endogenous antigens to MHC-class-II-loading compartments, direct viral nucleic acids to Toll-like receptors and regulate T-cell homeostasis. This Review describes the mechanisms of autophagy and highlights recent advances relevant to the role of autophagy in innate and adaptive immunity.