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Infection and Immunity, December 1999, p. 6394-6402, Vol. 67, No. 12
Departments of
Medicine,1 Microbiology and
Immunology,3 and Pathology and
Laboratory Medicine,4 Indiana University,
Indianapolis, Indiana 46202, and Department of
Microbiology, University of Texas Southwestern Medical Center,
Dallas, Texas 75235-90482
Received 1 June 1999/Returned for modification 28 July
1999/Accepted 10 September 1999
The immune response to Haemophilus ducreyi is mediated
in part by T cells infiltrating the site of infection. In this study, we show that H. ducreyi antigen preparations inhibited the
proliferation of peripheral blood mononuclear cells and primary human
T-cell lines. H. ducreyi also inhibited Jurkat T-cell
proliferation and induced apoptosis of Jurkat T cells, confirmed
through the detection of DNA degradation and membrane unpacking. The
cytotoxic product(s) was present in cell-free culture supernatant and
whole-cell preparations of H. ducreyi and was heat labile.
H. ducreyi produces two known heat-labile toxins, a
hemolysin and a cytolethal distending toxin (CDT). Whole cells and
supernatants prepared from a hemolysin-deficient mutant had the same
inhibitory and apoptotic effects on Jurkat T cells as did its isogenic
parent. Preparations made from an H. ducreyi cdtC mutant
were less toxic and induced less apoptosis than the parent. The toxic
activity of the cdtC mutant was restored by complementation
in trans. CdtC-neutralizing antibodies also inhibited
H. ducreyi-induced toxicity and apoptosis. The data suggest
that CDT may interfere with T-cell responses to H. ducreyi by induction of apoptosis.
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Cytolethal Distending Toxin of Haemophilus
ducreyi Induces Apoptotic Death of Jurkat T Cells
*
Corresponding author. Mailing address: Department of
Medicine, Emerson Hall, Rm. 435, 545 Barnhill Dr., Indianapolis, IN
46202. Phone: (317) 274-1427. Fax: (317) 274-1587. E-mail:
sspinola{at}iupui.edu.
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