V. Gelfanova et al., Cytolethal distending toxin of Haemophilus ducreyi induces apoptotic deathof Jurkat T cells, INFEC IMMUN, 67(12), 1999, pp. 6394-6402
The immune response to Haemophilus ducreyi is mediated in part by T cells i
nfiltrating the site of infection. Zn this study, we show that H. ducreyi a
ntigen preparations inhibited the proliferation of peripheral blood mononuc
lear cells and primary human T-cell lines. H. ducreyi also inhibited Jurkat
T-cell proliferation and induced apoptosis of Jurkat T cells, confirmed th
rough the detection of DNA degradation and membrane unpacking, The cytotoxi
c product(s) was present in cell-free culture supernatant and whole-cell pr
eparations of H. ducreyi and was heat labile. H. ducreyi produces two known
heat-labile toxins, a hemolysin and a cytolethal distending toxin (CDT). W
hole cells and supernatants prepared from a hemolysin-deficient mutant had
the same inhibitory and apoptotic effects on Jurkat T cells as did its isog
enic parent. preparations made from an H. ducreyi cdtC mutant,were less tox
ic and induced less apoptosis than the parent. The toxic activity of the cd
tC mutant was restored by complementation in trans, CdtC-neutralizing antib
odies also inhibited H. ducreyi-induced toxicity: and apoptosis, The data s
uggest that CDT may interfere with T-cell responses to H. ducreyi by induct
ion of apoptosis.