Iodination of bacteria: a bactericidal mechanism
01 Dec 1967-Journal of Experimental Medicine (The Rockefeller University Press)-Vol. 126, Iss: 6, pp 1063-1078
TL;DR: Iodination of the bacteria by the myeloperoxidase-iodide-H2O2 system was demonstrated chemically and radioautographically and suggests the involvement of labile intermediates of iodide oxidation rather than the more stable end products of oxidation such as iodine.
Abstract: Myeloperoxidase, iodide, and H2O2 have a bactericidal effect on Escherichia coli. Myeloperoxidase can be replaced in this system by lactoperoxidase or by a guinea pig leukocyte particulate preparation, H2O2 by an H2O2-generating system such as glucose and glucose oxidase, and iodide by thyroxine or triiodothyronine. The bactericidal effect was high at pH 5.0 and fell as the pH was increased. Preincubation of myeloperoxidase, iodide, and H2O2 for 30 min before the addition of the bacteria largely prevented the bactericidal effect. Thus, the organisms must be present in the reaction mixture during iodide oxidation for maximum killing, which suggests the involvement of labile intermediates of iodide oxidation rather than the more stable end products of oxidation such as iodine. Iodination of the bacteria by the myeloperoxidase-iodide-H2O2 system was demonstrated chemically and radioautographically. Iodination and the bactericidal effect were similarly affected by changes in experimental conditions in all the parameters tested (effect of preincubation, pH, and inhibitors). Phagocytosis of bacteria by guinea pig leukocytes was associated with the conversion of iodide to a trichloroacetic acid-precipitable form. Iodide was localized radioautographically in the cytoplasm of human leukocytes which contained ingested bacteria. Iodide fixation was not observed in the absence of phagocytosis or in the presence of Tapazole.
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TL;DR: O(2) (-) is made by leukocytes under circumstances which suggest that it may be involved in bacterial killing, and is identified as the agent responsible for the leukocyte-mediated reduction of cytochrome c.
Abstract: As a highly reactive substance produced in biological systems by the one-electron reduction of oxygen, superoxide (O(2) (-)) seemed a likely candidate as a bactericidal agent in leukocytes. The reduction of cytochrome c, a process in which O(2) (-) may serve as an electron donor, was found to occur when the cytochrome was incubated with leukocytes. O(2) (-) was identified as the agent responsible for the leukocyte-mediated reduction of cytochrome c by the demonstration that the reaction was abolished by superoxide dismutase, an enzyme that destroys O(2) (-), but not by boiled dismutase, albumin, or catalase. Leukocyte O(2) (-) production doubled in the presence of latex particles. The average rate of formation of O(2) (-) in the presence of these particles was 1.03 nmol/10(7) cells per 15 min. This rate, however, is only a lower limit of the true rate of O(2) (-) production, since any O(2) (-) which reacted with constituents other than cytochrome c would have gone undetected. Thus. O(2) (-) is made by leukocytes under circumstances which suggest that it may be involved in bacterial killing.
2,887 citations
TL;DR: Since Metschnikoff's discovery, hundreds of scientists studying dozens of species have reported thousands of studies on these cells, perhaps the most widely recognized of which are those of the eminent English scientists.
Abstract: (First of Two Parts) THE part played by phagocytes in defense against invading pathogens has been recognized since 1883. In that year, Metschnikoff, a Russian zoologist, reported that foreign particles injected into metazoans (in Metschnikoff's experiments, starfish larvae) were taken up by a population of "wandering mesodermal cells" that resided in interstitial tissues.1 He postulated a crucial role in host defense for these wandering cells, which he named "phagocytes." Since Metschnikoff's discovery, hundreds of scientists studying dozens of species have reported thousands of studies on these cells, perhaps the most widely recognized of which are those of the eminent English . . .
2,457 citations
TL;DR: It is concluded that the MPO system plays an important role in the microbicidal activity of phagocytes and the role of theMPO system in tissue injury.
Abstract: Neutrophilic polymorphonuclear leukocytes (neutrophils) are highly specialized for their primary function, the phagocytosis and destruction of microorganisms. When coated with opsonins (generally complement and/or antibody), microorganisms bind to specific receptors on the surface of the phagocyte and invagination of the cell membrane occurs with the incorporation of the microorganism into an intracellular phagosome. There follows a burst of oxygen consumption, and much, if not all, of the extra oxygen consumed is converted to highly reactive oxygen species. In addition, the cytoplasmic granules discharge their contents into the phagosome, and death of the ingested microorganism soon follows. Among the antimicrobial systems formed in the phagosome is one consisting of myeloperoxidase (MPO), released into the phagosome during the degranulation process, hydrogen peroxide (H2O2), formed by the respiratory burst and a halide, particularly chloride. The initial product of the MPO-H2O2-chloride system is hypochlorous acid, and subsequent formation of chlorine, chloramines, hydroxyl radicals, singlet oxygen, and ozone has been proposed. These same toxic agents can be released to the outside of the cell, where they may attack normal tissue and thus contribute to the pathogenesis of disease. This review will consider the potential sources of H2O2 for the MPO-H2O2-halide system; the toxic products of the MPO system; the evidence for MPO involvement in the microbicidal activity of neutrophils; the involvement of MPO-independent antimicrobial systems; and the role of the MPO system in tissue injury. It is concluded that the MPO system plays an important role in the microbicidal activity of phagocytes.
2,070 citations
Cites background from "Iodination of bacteria: a bacterici..."
...Although thyroxine can substitute for the halide in the MPOH2O2-halide antimicrobial system [69], throxine is deiodinated under these conditions [204, 205], raising the possibility that the released iodide may be the required microbicidal component....
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...When iodide is the halide, iodination is detected [69]....
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...The iodinated hormone, thyroxine, can substitute for iodide in the cell-free MPO system [69], presumably, at least in part, as a result of its deiodination by the peroxidase system [204, 205]....
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TL;DR: Killing was previously believed to be accomplished by oxygen free radicals and other reactive oxygen species generated by the NADPH oxidase, and by oxidized halides produced by myeloperoxidase, but this is incorrect.
Abstract: Neutrophils provide the first line of defense of the innate immune system by phagocytosing, killing, and digesting bacteria and fungi. Killing was previously believed to be accomplished by oxygen free radicals and other reactive oxygen species generated by the NADPH oxidase, and by oxidized halides produced by myeloperoxidase. We now know this is incorrect. The oxidase pumps electrons into the phagocytic vacuole, thereby inducing a charge across the membrane that must be compensated. The movement of compensating ions produces conditions in the vacuole conducive to microbial killing and digestion by enzymes released into the vacuole from the cytoplasmic granules.
1,672 citations
TL;DR: Neutrophils are one of the professional phagocytes in humans that ingest bacteria into intracellular spaces and are involved in phagocytosis.
1,569 citations
References
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TL;DR: More rapid than previous techniques, this method gives blocks which do not fracture unduly on trimming and provides sections of soft tissues at 1 μ for phase contrast microscopy, as well as ultrathin sections which cut as easily with glass knives as sections of methacrylate.
Abstract: Fixed tissue is dehydrated with tertiary butyl alcohol overnight. The following day it is cleared in toluene, infiltrated and embedded in Araldite resin-hardener-accelerator mixture without dibutyl...
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"Iodination of bacteria: a bacterici..." refers methods in this paper
...After appropriate exposure at 6°C, the radioantograms were developed, and the smears stained with a mixture of methylene blue and azure II (21)....
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TL;DR: A method is described for demonstrating leukocyte peroxidase activity in which benzidine dihydrochloride is used as the indicator compound instead of the more commonly used but potentially more hazardous benzidine base.
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639 citations
"Iodination of bacteria: a bacterici..." refers background in this paper
...First, it has been reported (35) that H~O2 is formed in the leukocyte during the period of accelerated metabolism which follows phagocytosis; and second, the intracelhlar pH in the vicinity of the ingested particle has been reported to be distinctly acid (36), i....
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TL;DR: The use of benzidine base as an indicator of leukocyte peroxidase activity has been of practical value to the hematologist since the beginning of the present century.
452 citations
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