THBD and viral infectious disease: Plasmacytoid DC (PDC) produce high amounts of type I IFNs during viral infections (5), they are characterized by CD123, blood DC antigens BDCA-2 (CD303) and BDCA-4 (CD304), expression while myeloid DC (MDC, also named conventional or classical DCs, cDC) express CD11c or BDCA-3 (CD141; ref. 6).