Galectin-3 (gal3) is known for its immunoregulatory functions in infectious, autoimmune, and inflammatory diseases. However, little is known about its regulatory role in the host's
IL-17A response to
infection. Using a mouse model of
histoplasmosis in which both Th1 and Th17 responses contribute to fungal clearance, we investigated how gal3 regulates
IL-17A responses. Our study showed that
Histoplasma infection induced gal3(-/-) dendritic cells to produce significantly higher levels of
IL-23, TGF-β1, and IL-1β than did gal3(+/+) cells. Infected by the same inoculum of Histoplasma, gal3(-/-) mice had lower fungal burden and produced higher levels of IL-23/IL-17-axis
cytokines and lower levels of
IL-12 and IFN-γ. Additionally, there was an increase in Th17 cells and a reduction in Th1 cells in infected gal3(-/-) mice. In vitro Th1/Th17-skewing experiments excluded the intrinsic effect of gal3 on Th cell differentiation. Although neutrophils from both gal3(+/+) and gal3(-/-) mice produced
IL-17A upon
IL-23 stimulation, their contribution to
IL-17A production was greater in gal3(-/-) mice than in gal3(+/+) mice. Compared with gal3(+/+) dendritic cells, adoptive transfer of gal3(-/-) dendritic cells resulted in production of significantly higher levels of IL-17-axis
cytokines and reduced fungal burden. It appears that reduced fungal burden and preferential
IL-17A response in gal3(-/-) mice by both Th17 cells and neutrophils were the result of preferential production of IL-23/IL-17-axis
cytokines by dendritic cells. Our study showed that gal3 negatively regulates
IL-17A responses through inhibition of IL-23/IL-17-axis
cytokine production by dendritic cells.