pDCs are not only professional producers of IFN-I and key players in innate immune defenses against viral infections. They have also demonstrated ability to contribute to the induction and regulation of adaptive immunity. Depending on the maturation signals they receive as well as on the nature and concentration of the antigen, pDCs can have contrasting effects on adaptive immunity (Scheme 1). They can promote anti-viral cellular adaptive immunity either directly through crosspresentation of exogenous antigens to CD8 T cells or indirectly through the promotion of cDC maturation. On the contrary, under different conditions, they can induce immune tolerance.