title: Differences in the rate of intracellular killing of catalase-negative and catalase-positive Listeria monocytogenes by normal and interferon-gamma-activated macrophages.
abstract: Intracellular killing of catalase-positive bacteria by murine resident macrophages requires the presence of extracellular serum, whereas killing of catalase-negative bacteria can occur in the absence of serum. To find out whether the intracellular killing of bacteria by rIFN-gamma-activated macrophages also requires serum stimulation, we investigated the handling of ingested catalase-negative and -positive Listeria monocytogenes by peritoneal macrophages of normal Swiss mice and mice injected i.p. with 1 x 10(4) U rIFN-gamma 18 h earlier. In the absence of extracellular serum, rIFN-gamma-activated macrophages killed ingested catalase-negative Listeria more efficiently (P < 0.01) than normal resident macrophages. Maximal killing of catalase-negative bacteria by rIFN-gamma-activated macrophages required an extracellular serum concentration of only 1.0 to 2.5% compared with the 10% needed by normal macrophages. No differences were observed in the rates of intracellular killing of catalase-positive Listeria by rIFN-gamma-activated and normal resident macrophages: both populations of macrophages required 10% extracellular serum for maximal killing of these bacteria, and killing was minimal in the absence of serum. The rIFN-gamma-activated macrophages displayed enhanced O2-consumption after stimulation with phorbol myristate acetate and heat-killed Listeria compared with macrophages from normal mice. These findings indicate that, under suboptimal stimulation by extracellular serum, rIFN-gamma enhances the intracellular killing of catalase-negative Listeria which lack endogenous catalase acting as a scavenger of reactive oxygen intermediates. The mechanism underlying the enhancement is probably the amplification of the respiratory burst by IFN-gamma.
authors: Department of Infectious Diseases, University Hospital Leiden, The Netherlands.
authors: J T
authors: JT
authors: van Dissel
authors: J J
authors: JJ
authors: Stikkelbroeck
authors: R
authors: R
authors: van Furth
mesh_terms: D000818:Animals; D002374:Catalase / Q000032:analysis; D003602:Cytotoxicity, Immunologic / Q000276:immunology; D007371:Interferon-gamma / Q000494:pharmacology*; D008089:Listeria monocytogenes / Q000201:enzymology / Q000276:immunology*; D008262:Macrophage Activation / Q000276:immunology; D008264:Macrophages / Q000187:drug effects / Q000276:immunology*; D008297:Male; D051379:Mice; D010101:Oxygen Consumption / Q000276:immunology; D010537:Peritoneum / Q000166:cytology; D011994:Recombinant Proteins / Q000276:immunology; D013047:Specific Pathogen-Free Organisms
chemical_list: D011994:Recombinant Proteins; D007371:Interferon-gamma; D002374:Catalase