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Infect. Immun., 05 1997, 1793-1799, Vol 65, No. 5
Y Ozeki, K Kaneda, N Fujiwara, M Morimoto, S Oka and I Yano
It is reported that some bacteria or bacterial components cause thymic
atrophy via the apoptotic process. The present study demonstrated for the
first time in vivo induction of apoptosis in the mouse thymus by
mycobacterial cord factor (CF) (trehalose 6,6'-dimycolate). When 300 microg
of purified CF from Mycobacterium tuberculosis was intravenously
administered to BALB/c mice in the form of water-in-oil-in-water (w/o/w)
emulsion, thymic atrophy and pulmonary granulomas were induced with a peak
on day 7, whereas, in the form of liposomes, CF induced thymic atrophy on
days 14 to 21 in parallel with the development of hepatic granulomas.
Thymic atrophy resulted from the depletion of cortical lymphocytes via
apoptosis as revealed by DNA fragmentation and karyorrhectic changes. In
contrast, mycobacterial sulfatide (2,3,6,6'- tetraacyl trehalose
2'-sulfate) caused neither thymic atrophy nor granuloma formation. Compared
to lipopolysaccharide-induced thymocyte apoptosis, CF (w/o/w)-induced
thymocyte apoptosis developed more slowly, reached a maximum later, and
lasted longer but was less intense. Although serum tumor necrosis factor
alpha (TNF-alpha) levels in CF-treated mice were not significantly
elevated, administration of anti-TNF-alpha antibody almost completely
inhibited thymic atrophy and granuloma formation. Serum corticosterone
levels were only slightly elevated by CF administration. The present
results indicate that mycobacterial CF induces thymic atrophy via
apoptosis, which is closely linked with granuloma formation.
Copyright © 1997, American Society for Microbiology
In vivo induction of apoptosis in the thymus by administration of mycobacterial cord factor (trehalose 6,6'-dimycolate)
Department of Bacteriology, Osaka City University Medical School, Osaka, Japan.
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