pDCs [MHC IIint CD11cint B220+ lymphocyte antigen 6 family C (Ly6C)+ bone marrow stromal cell antigen 2 (BST2)+ Sialic acid-binding immunoglobulin-like lectin H (Siglec-H)+ in mice and HLA-DR+CD11c− CD4+ blood dendritic cell antigen (BDCA)2+ BDCA4+ CD123+ in humans] are derived from both myeloid and lymphoid progenitors, and they can rapidly secrete type I interferon in response to viral infection [47]. Here, BST2 is linked to viral infectious disease.