In summary, pDCs are equipped with a unique set of sensors and associated signaling pathways to rapidly sense a variety of viruses, in particular herpesviruses, and to respond by high level production of IFN-I and other innate cytokines or chemokines, while protecting themselves from viral infection. In this respect, pDCs appear to play an important, non redundant role in vivo in innate immune defense against herpesviruses and other viruses such as mouse hepatitis virus [78] . However, pDC activation during viral infections appears to be tightly controlled in intensity, space, and time, by a variety of mechanisms, which may be in place to tune the risk of cytokine shock to the level of threat posed to a specific host by a given viral infection.