ABSTRACT
Macroautophagy is a conserved intracellular homeostatic mechanism for the degradation of cytosolic constituents. Autophagy can promote cell survival by providing essential amino acids from the breakdown of macromolecules during periods of nutrient deprivation, and can remove damaged or excess organelles, such as mitochondria and peroxisomes. More recently, autophagy has been shown to play an important role in innate and adaptive immune responses to pathogenic bacteria in macrophages and dendritic cells. This unit presents protocols for the measurement of autophagy in macrophages.
Subject(s)
Autophagy/physiology , Cytological Techniques/methods , Macrophages/cytology , Macrophages/physiology , Adaptor Proteins, Signal Transducing/analysis , Animals , Cadaverine/analogs & derivatives , Cadaverine/analysis , Fluorescent Antibody Technique/methods , Fluorescent Dyes/analysis , Humans , Immunoblotting/methods , Indicators and Reagents/chemistry , Microtubule-Associated Proteins/analysis , Phagosomes/chemistry , Staining and Labeling/methodsABSTRACT
Autophagy is a major intracellular pathway for the lysosomal degradation of long-lived cytoplasmic macromolecules and damaged or surplus organelles. More recently, autophagy has also been linked with innate and adaptive immune responses against intracellular pathogens, including Mycobacterium tuberculosis, which can survive within macrophages by blocking fusion of the phagosome with lysosomes. Induction of autophagy by the Th1 cytokine IFN-gamma enables infected macrophages to overcome this phagosome maturation block and inhibit the intracellular survival of mycobacteria. Conversely, the Th2 cytokines IL-4 and IL-13 inhibit autophagy in murine and human macrophages. We discuss how differential modulation of autophagy by Th1 and Th2 cytokines may represent an important feature of the host response to mycobacteria.
Subject(s)
Autophagy/physiology , Cytokines/physiology , Macrophages/microbiology , Macrophages/physiology , Mycobacterium tuberculosis/physiology , Animals , Humans , Immunity, Innate , Interferon-gamma/physiology , Interleukin-13/physiology , Interleukin-4/physiology , Phagosomes , Th1 Cells/immunology , Th2 Cells/immunologyABSTRACT
Autophagy is a recently recognized immune effector mechanism against intracellular pathogens. The role of autophagy in innate immunity has been well established, but the extent of its regulation by the adaptive immune response is less well understood. The T helper 1 (Th1) cell cytokine IFN-gamma induces autophagy in macrophages to eliminate Mycobacterium tuberculosis. Here, we report that Th2 cytokines affect autophagy in macrophages and their ability to control intracellular M. tuberculosis. IL-4 and IL-13 abrogated autophagy and autophagy-mediated killing of intracellular mycobacteria in murine and human macrophages. Inhibition of starvation-induced autophagy by IL-4 and IL-13 was dependent on Akt signaling, whereas the inhibition of IFN-gamma-induced autophagy was Akt independent and signal transducer and activator of transcription 6 (STAT6) dependent. These findings establish a mechanism through which Th1-Th2 polarization differentially affects the immune control of intracellular pathogens.
