Type I IFN are extremely pleiotropic cytokines. For instance, they are involved in defense against many viruses [45] [46] [47] , could be either protective or detrimental during non-viral pathogens [7, 8] , act in cancer surveillance [48, 49] , but they are also effector molecules in toxic shock elicited by LPS [50] and TNF [51] . In addition, recombinant type I IFN is used in the clinics as therapy against certain cancers as well as for treatment of chronic infections caused by HBV [52] , HCV [53] and multiple sclerosis [54] . Thus, these molecules could be of great health benefit but could also elicit serious detrimental effects. Therefore, knowledge about the cells involved in production of type I IFN and their regulation is of utmost importance for the understanding of the IFN system.