In humans, the administration of a monoclonal antibody against blood DC antigen 2(BDCA2) expressed on pDCs decreased expression of IFN response genes in the blood, and reduced disease activity of skin disease and arthritis in SLE, suggesting that pDCs may indeed be an important source of type I IFNs in SLE (52–54). The gene discussed is CLEC4C; the disease is systemic lupus erythematosus.