Mechanisms of Dectin-1 dependent IL-17A production during invasive fungal infection. (56.14)

Abstract

Abstract In the current work, we show that mice deficient in the beta-glucan receptor Dectin-1 demonstrate significantly reduced levels of IL-17A in the lungs 48 h after Aspergillus fumigatus (AF) challenge. Culturing cells from enzymatic lung digests ex vivo further demonstrated Dectin-1 dependent IL-17A production, providing a sensitive method to identify mechanisms associated with lung IL-17A production after AF challenge. Neutralization of IL-23, but not IL-1β or IL-6, in WT lung digest cell cultures reduced IL-17A production by 60%. Lung digest cells from AF-challenged Rorc-/- deficient mice had attenuated IL-17A production, however, Rorc and Rora mRNA, and RORγt protein, expression was not impaired in lung digest cells from Dectin-1 KO mice. Ahr, Irf4 and Card9 mRNA expression was also unchanged. Intracellular cytokine staining revealed that CD11b+ and CD11b+ Ly-6G+ cells were sources of IL-17A, although only CD11b+ Ly-6G+ cells produced IL-17A in a Dectin-1 dependent manner. In turn, Ly-6G+ cells purified from the lungs of AF-challenged Dectin-1 KO mice displayed a 2-fold reduction in Il17a mRNA expression, yet increased Rorc and Rora mRNA expression. IL-23R+ cells in lung digest were predominantly CD11b+ Ly-6G+ cells. In summary, Dectin-1 dependent innate IL-17A production in the lungs during invasive fungal infection is mediated in part by CD11b+ Ly-6G+ neutrophils, which is partially dependent on IL-23. Dectin-1 deficiency does not, however, compromise induction of Rorc.