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Critical Reviews™ in Immunology
CiteScore™: 2.19 IF: 1.352 5-Year IF: 3.347 SNIP: 0.55 SJR: 1.022

ISSN Print: 1040-8401
ISSN Online: 2162-6472

Critical Reviews™ in Immunology

DOI: 10.1615/CritRevImmunol.v21.i5.10
28 pages

Macrophage Arginine Metabolism to Ornithine/Urea or Nitric Oxide/Citrulline: A Life or Death Issue

Charles D. Mills
Department of Surgery and Diabetes Institute for Immunology and Transplantation, Department of Surgery, University of Minnesota Hospitals and Clinics, Box 120, 420 Delaware St. SE, Minneapolis, MN 55455

ABSTRACT

Macrophages can metabolize arginine to nitric oxide in quantities that inhibit pathogens or nearby host cells. They can instead metabolize arginine to ornithine (a precursor of polyamines and collagen) in quantities that stimulate pathogens or nearby host cells. Macrophages are essentially the only circulating cells that can make these life or death decisions with arginine. Macrophages expressing these destructive or constructive phenotypes have been termed M-1 or M-2 because they also stimulate TH1 or TH2 responses, respectively. Factors that influence whether a macrophage expresses the M-1 or M-2 phenotype and the real or potential impact on immune responses and other host processes are discussed.