Autophagy as an immune defense mechanism.

Autophagy is a homeostatic process whereby cytosol or intracellular organelles are sequestered by a double membrane structure termed autophagosome for subsequent delivery to lysosomes and degradation. Autophagy takes part in cell survival and death and has been implicated in development, aging, neurodegeneration and cancer. The newly discovered specialized role of autophagy in immune cells expands autophagic functions to defense against intracellular pathogens. Furthermore, autophagy is involved in acquired immunity, such as antigen processing for MHC II presentation, and is modulated by cytokines such as IFN-gamma. A further link has emerged between autophagy and defense against intracellular pathogens via the immunity-related GTPase lrgm1 (LRG-47), which has a protective role against Mycobacterium tuberculosis. We propose the term immunophagy for these defense processes.