Neutrophils Produce Interleukin 17A (IL-17A) in a Dectin-1- and IL-23-Dependent Manner during Invasive Fungal Infection

2011 
We have previously reported that compromised interleukin 17A (IL-17A) production in the lungs increased susceptibility to infection with the invasive fungal pathogen Aspergillus fumigatus. Here we have shown that culturing lung cells from A. fumigatus-challenged mice ex vivo demonstrated Dectin-1-dependent IL-17A production. In this system, neutralization of IL-23 but not IL-6, IL-1, or IL-18 resulted in attenuated IL-17A production. Il23 mRNA expression was found to be lower in lung cells from A. fumigatus-challenged Dectin1-deficient mice, whereas bone marrow-derived dendritic cells from Dectin-1-deficient mice failed to produce IL-23 in response to A. fumigatus in vitro. Addition of recombinant IL-23 augmented IL-17A production by wild-type (WT) and Dectin-1-deficient lung cells, although the addition of IL-6 or IL-1 did not augment the effect of IL-23. Intracellular cytokine staining of lung cells revealed lower levels of CD11b IL-17A and Ly-6G IL-17A cells in A. fumigatus-challenged Dectin-1-deficient mice. Ly-6G neutrophils purified from the lungs of A. fumigatus-challenged Dectin-1-deficient mice displayed lower Il17a mRNA expression but surprisingly had intact Rorc and Rora mRNA expression. We further demonstrated that Ly-6G neutrophils required the presence of myeloid cells for IL-17A production. Finally, upon in vitro stimulation with A. fumigatus, thioglycolate-elicited peritoneal neutrophils were positive for intracellular IL-17A expression and produced IL-17A in a Dectin-1- and IL-23-dependent manner. In summary, Dectin-1-dependent IL-17A production in the lungs during invasive fungal infection is mediated in part by CD11b Ly-6G neutrophils in an IL-23dependent manner.
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