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Phagocytosis and killing of Mycobacterium avium complex by human neutrophils
Author(s) -
Hartmann Pia,
Becker Ralph,
Franzen Caspar,
SchellFrederick Elisabeth,
Römer Jens,
Jacobs Michaela,
Fätkenheuer Gerd,
Plum Georg
Publication year - 2001
Publication title -
journal of leukocyte biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.819
H-Index - 191
eISSN - 1938-3673
pISSN - 0741-5400
DOI - 10.1189/jlb.69.3.397
Subject(s) - phagocytosis , flow cytometry , biology , microbiology and biotechnology , neutrophile , granulocyte , macrophage , immune system , mycobacterium , fluorescence microscope , intracellular , immunology , bacteria , fluorescence , inflammation , in vitro , biochemistry , genetics , quantum mechanics , physics
Organisms belonging to the Mycobacterium avium complex (MAC) cause life‐threatening bacteremia in immunocompromised patients. Monocytes and macrophages are thought to be responsible for ingestion and killing of MAC. However, it has been suggested that neutrophils may play a role in the early immune response to MAC infection. Here, neutrophils in autologous plasma were incubated (at 0 and 37°C) with M. avium labeled with Auramine O, a potent fluorochrome. Neutrophil phagocytosis was measured by flow cytometry. Neutrophils incubated at 37°C showed an increase in fluorescence over time with a maximum at 15 min, whereas neutrophils on ice showed no time‐dependent increase in FL1. At 15 min Fl 1 at 37°C was twice as high as FL1 at 0°C. Examination under the fluorescent microscope showed multiple intracellular fluorescent mycobacteria. Results in nine independent experiments showed time‐dependent decrease of colony‐forming units in neutrophil‐associated live M. avium . Significant killing was observed within 30 min and was complete by 120 min. Observation by electron microscopy clearly confirmed the presence of intraphagosomal MAC, both intact and with evidence of degradation. These data demonstrate that MAC is rapidly phagocytized and killed by human neutrophils. The newly established flow cytometry method should be useful in further studies of neutrophil function and of the role of G‐CSF and other cytokines in MAC disease.