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Infect. Immun., 12 1996, 4900-4906, Vol 64, No. 12
A Muller, J Hacker and BC Brand
Legionella pneumophila, the causative agent of Legionnaires' disease and
Pontiac fever, replicates within and eventually kills human macrophages. In
this study, we show that L. pneumophila is cytotoxic to HL-60 cells, a
macrophage-like cell line. We demonstrate that cell death mediated by L.
pneumophila occurred at least in part through apoptosis, as shown by
changes in nuclear morphology, an increase in the proportion of fragmented
host cell DNA, and the typical ladder pattern of DNA fragmentation
indicative of apoptosis. We further sought to determine whether potential
virulence factors like the metalloprotease and the macrophage infectivity
potentiator of L. pneumophila are involved in the induction of apoptosis.
None of these factors are essential for the induction of apoptosis in HL-60
cells but may be involved in other cytotoxic mechanisms that lead to
accidental cell death (necrosis). The ability of L. pneumophila to promote
cell death may be important for the initiation of infection, bacterial
survival, and escape from the host immune response. Alternatively, the
triggering of apoptosis in response to bacterial infection may have evolved
as a means of the host immune system to reduce or inhibit bacterial
replication.
Copyright © 1996, American Society for Microbiology
Evidence for apoptosis of human macrophage-like HL-60 cells by Legionella pneumophila infection
Institut fur Molekulare Infektionsbiologie, Universitat Wurzburg, Germany.
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