Cytosolic DNA recognition for triggering innate immune responses

The detection of microbial components by pattern recognition receptors (PRRs) and the subsequent triggering of innate immune responses constitute the first line of defense against infections. Recently, much attention has been focused on cytosolic nucleic acid receptors; the activation of these receptors commonly evokes a robust innate immune response, the hallmark of which is the induction of type I interferon (IFN) genes. In addition to receptors for RNA, receptors that detect DNA exposed in the cytosol and activate innate immune responses have long been thought to exist. Recently, DAI (DLM-1/ZBP1) has been identified as a candidate cytosolic DNA sensor. Cytosolic signaling by DNA-activated DAI (DLM-1/ZBP1) signaling results in activation of the two pathways of gene transcription critical to innate immune responses, the IRF and NF-kappaB pathways. In this review, we summarize our current view of activation mechanism and immunological roles of DAI (DLM-1/ZBP1) and related molecules. In addition, we also discuss the issue of self vs. non-self DNA recognition by DAI (DLM-1/ZBP1) and other DNA sensors in terms of the possible involvement in autoimmune abnormalities.