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Infection and Immunity, January 1999, p. 395-402, Vol. 67, No. 1
Institute of Hygiene, University of
Innsbruck, Innsbruck, Austria
Received 24 June 1998/Returned for modification 21 July
1998/Accepted 15 October 1998
Multinucleated giant cells (MGC), a characteristic feature of
tuberculous granulomas, form by fusion of monocytes or macrophages, but
little is known about the mechanism of the fusion process itself.
Several studies report an indirect effect of mycobacteria, i.e.,
induction of a soluble lymphocyte-derived fusion factor following
stimulation by mycobacteria or mycobacterial products. The aim of our
study was to determine whether contact with mycobacteria can induce MGC
formation from human monocytes in vitro. Stimulation of monocytes with
Mycobacterium bovis bacillus Calmette-Guérin (BCG) in
combination with cytokine-containing supernatants of herpesvirus
saimiri-transformed human T-cell clones (T-SN) led to MGC formation
with fusion rates of about 27%. In contrast, stimulation with one
component alone induced only low fusion rates of up to 10%.
Heat-killed BCG in combination with T-SN induced monocyte fusion to the
same extent as live mycobacteria. BCG culture supernatant, BCG lysate,
or inert particles in combination with T-SN did not induce MGC
formation. Experiments using transwell plates containing a
semipermeable membrane revealed that induction of the fusion process is
dependent on direct contact of monocytes and mycobacteria. MGC
formation induced by BCG plus T-SN could be inhibited by addition of
monoclonal antibodies to gamma interferon (but not tumor necrosis
factor alpha) as well as to the
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Generation of Multinucleated Giant Cells In Vitro
by Culture of Human Monocytes with Mycobacterium bovis BCG
in Combination with Cytokine-Containing Supernatants
chain (CD18) of
2-integrins.
These results demonstrate that contact with mycobacteria in combination
with cytokine-containing supernatants is able to induce human monocytes
to form MGC and that membrane-bound molecules of mycobacteria and
monocytes are involved in the fusion process.
*
Corresponding author. Mailing address: Institut
für Hygiene, Fritz-Pregl-Str. 3, A-6020 Innsbruck, Austria.
Phone: 43-512-507-3405. Fax: 43-512-507-2870. E-mail:
johannes.moest{at}uibk.ac.at.
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