Immunometabolism within the tuberculosis granuloma: amino acids, hypoxia, and cellular respiration.
Tuberculosis (TB) granulomas are compact, organized agglomerations of infected and uninfected macrophages, T cells, neutrophils, and other immune cells. Within the granuloma, several unique metabolic adaptations occur to modify the behavior of immune cells, potentially favoring bacterial persistence balanced with protection against immunopathology. These include the induction of arginase-1 in macrophages to temper nitric oxide (NO) production and block T cell proliferation, inhibition of oxygen-requiring NO production in hypoxic regions, and induction of tryptophan-degrading enzymes that modify T cell proliferation and function. The spatial and time-dependent organization of granulomas further influences immunometabolism, for example through lactate production by activated macrophages, which can induce arginase-1. Although complex, the metabolic changes in and around TB granulomas can be potentially modified by host-directed therapies. While elimination of the TB bacilli is often the goal of any anti-TB therapy, host-directed approaches must also account for the possibility of immunopathologic damage to the lung.
Department of Pediatrics, Division of Infectious Diseases, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA. joseph.qualls@cchmc.org.
Joseph E
JE
Qualls
Department of Infectious Diseases and Department of Immunology, St. Jude Children's Research Hospital, Memphis, TN, USA. peter.murray@stjude.org.
Peter J
PJ
Murray
D000222:Adaptation, Physiological; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D001120:Arginine / Q000378:metabolism; D019069:Cell Respiration; D003094:Collagen / Q000378:metabolism; D004734:Energy Metabolism; D006099:Granuloma / Q000209:etiology* / Q000378:metabolism*; D054884:Host-Pathogen Interactions / Q000276:immunology; D006801:Humans; D000860:Hypoxia / Q000276:immunology / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology; D008264:Macrophages / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D009569:Nitric Oxide / Q000096:biosynthesis; D026361:Reactive Nitrogen Species / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D013312:Stress, Physiological; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D014364:Tryptophan / Q000378:metabolism; D014376:Tuberculosis / Q000150:complications / Q000276:immunology* / Q000382:microbiology / Q000473:pathology*
D000596:Amino Acids; D026361:Reactive Nitrogen Species; D017382:Reactive Oxygen Species; D009569:Nitric Oxide; D014364:Tryptophan; D003094:Collagen; D001120:Arginine
Granuloma; Hypoxia; L-arginine; L-tryptophan; Metabolism; Tuberculosis