Background: Dendritic cells (DCs) with both proinflammatory and tolerogenic properties have been implicated in modulation of CD4⁺ T cell responses in many fungal diseases. However, the role of DC in the context of Talaromyces marneffei  (T. marneffei ) infection has not been determined. In this study, we aimed to study the effect of the yeast form of T. marneffei  yeasts on DCs, as well as the role of DCs in modulating T helper 17 (Th17) and regulatory T (Treg) cell responses to the pathogen.
Methods: Mouse bone marrow-derived DCs were stimulated with T. marneffei  yeasts for 24 h. Frequencies of CD80 and CD86 expression on DCs and the levels of IL-6, IL-10 and TGF-β in the culture supernatant of yeast-stimulated DCs were detected by flow cytometry and ELISA, respectively. In co-culture experiments, CD4⁺ T lymphocytes of mice were isolated from the spleen using magnetic beads and co-cultured with T. marneffei  yeasts, with or without DCs for 24 h. The proportions of Th17 and Treg cells in co-culture were detected by flow cytometry. The mRNA levels of RORγt  and Foxp3  were detected by RT-PCR. Levels of IL-10 and TGF-β in the co-culture supernatant were detected by ELISA.
Results: The expressions of CD80 and CD86 on DCs were increased, as well as IL-6, IL-10 and TGF-β levels in the culture supernatant of T. marneffei -stimulated DCs were higher than those in DCs cultured without T. marneffei . In co-culture experiments, in the presence of DCs, T. marneffei  promoted Treg expansion and Foxp3 up-regulation but limited Th17 and downregulated RORγt. Levels of IL-10 and TGF-β were higher in the co-culture containing DCs than without DCs.
Conclusion: Our findings demonstrated that the interaction between DCs and T. marneffei  could promote Treg expansion but not Th17 generation. These findings provide a mechanism by which DCs may promote immune tolerance in T. marneffei  infection.
Keywords: dendritic cells, Talaromyces marneffei , Th17 cells, Treg cells