Although type I interferons (IFN-α/β) have been traditionally associated with antiviral responses, their importance in host defense against bacterial pathogens is being increasingly appreciated. Little is known, however, about the occurrence and functional role of IFN-α/β production in response to pathogenic yeasts. Here, we found that conventional DCs, but not macrophages nor plasmacytoid DCs, mounted IFN-β responses after in vitro stimulation with Candida spp. or Saccharomyces cerevisiae. These responses absolutely required MyD88, a Toll-like receptor (TLR) adaptor molecule, and were partially dependent on TLR9 and TLR7. Moreover, Candida DNA, as well as RNA, could recapitulate the IFN-β response. After intravenous challenge with Candida albicans, most mice lacking the IFN-α/β receptor died from their inability to control fungal growth, whereas all WT controls survived. These data suggest that recognition of yeast nucleic acids by TLR7 and TLR9 triggers a host-protective IFN-α/β response.
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