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Infect. Immun., 01 1997, 298-304, Vol 65, No. 1
J Keane, MK Balcewicz-Sablinska, HG Remold, GL Chupp, BB Meek, MJ Fenton and H Kornfeld
The effect of Mycobacterium tuberculosis infection on the viability of
healthy (control) human alveolar macrophages was evaluated by staining with
ethidium homodimer and calcein to discriminate live from dead cells.
Infection with M. tuberculosis H37Ra or H37Rv increased macrophage
mortality at 6 days from the control level of 3.8% +/- 0.7% to 28.7% +/-
6.9% or 12.6% +/- 3.1%, respectively (P < 0.001 for comparisons of all
conditions). A role for tumor necrosis factor alpha (TNF-alpha) in the M.
tuberculosis-induced cytolysis of alveolar macrophages was demonstrated by
increased cytotoxicity following the addition of exogenous TNF-alpha to the
cultures and by enhancement of macrophage survival when M.
tuberculosis-infected alveolar macrophages were treated with pentoxifylline
or anti-TNF-alpha antibody. The cytolytic mechanism was determined to be
apoptosis by the demonstration of a characteristic internucleosomal ladder
of genomic DNA by agarose gel electrophoresis, by finding nuclear
fragmentation and condensation by electron microscopy, and by in situ
terminal transferase-mediated nick end labeling of fragmented DNA in
alveolar macrophages infected with M. tuberculosis in vitro. The latter
technique was employed to reveal extensive apoptosis within caseating
granulomas from lung tissue samples from clinical tuberculosis cases. The
induction of apoptosis in alveolar macrophages by M. tuberculosis may play
a role in the macrophage-pathogen interaction of tuberculosis in vivo.
Copyright © 1997, American Society for Microbiology
Infection by Mycobacterium tuberculosis promotes human alveolar macrophage apoptosis
Pulmonary Center, Boston University School of Medicine, Massachusetts 02118, USA.
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