Abstract: In order to elucidate the role of APCs in chancroid, the phagocytic activities and cytokine secretion profiles (TNF-α, IL-1α, IL-6 and IL-8) of the APCs were analyzed after 6 h, 24 h exposure to Haemophilus Influenzae, Haemophilus ducreyi bacteria and its purified antigens[H. ducreyi lipooligosaccharide (LOS) and cytolethal distending toxin (HdCDT)]. Furthermore, T-cell proliferation and cytokine (IFN-α, IL-4, IL-13) release were examined after co-culturing isolated autologous CD 4 + T-cells with antigen-pulsed APCs for 24 h. Results: Between 6% and 27% of the DCs, MQs phagocytosed different H. ducreyi strains, as wells as H. influenzae and E. coli. All of the H. ducreyi strains induced strong secretion of TNF-α, IL-6, IL-8(P<0.05); The purified LOS induced 2-to-3-fold lower levels of pro-inflammatory cytokines than whole bacteria, whereas HdCDT did not induce detectable levels of these cytokines. High levels of IFN-α and T-cell proliferation were induced by either DCs or MQs that were pre-exposed to H. ducreyi and H. influenzae bacteria. HdCDT-treated DCs and MQs did not induce T-cell proliferative responses and IFN-α secretion. Conclusions: H. ducreyi influences T-cell-stimulatory ability of APCs and favors a Th1-type response.

Key words: dendritic cells, macrophages, Haemophilus ducreyi, Haemophilus influenzae