As discussed above, pDCs are potent antiviral cells which can produce high levels of a number of cytokines or chemokines and strongly stimulate both the innate and adaptive immune systems. Although pDC functions are regulated by a number of activating or inhibitory mechanisms, situations have been described where pDC responses are deleterious for the host. The role of pDCs in the development of autoimmune diseases, including SLE or psoriasis, have been discussed in detail elsewhere [135] . Recent data have also suggested a possible deleterious role of pDCs in the context of certain viral infections. This should not be a surprise considering that IFN-I have long been known to be a double-edged sword able to promote either health or disease depending on the physiopathological context (Table 2) .