Plasmacytoid dendritic cells (pDC) are the most powerful producers of interferon-I (IFN-I), but also display other functions like cytotoxicity, production of other cytokines and antigen presentation. Recently, two alphaherpesvirus proteins were identified (US3 and gB) that modulate IFN-I production by pDC. We will investigate the molecular mechanism underlying this modulation and whether the other functions of pDC are also modulated.