IFNA1 and Arthritis: Synovial pDCs can produce robust IFN-α, and persistent arthritis has been induced by intra-articular transfer of IFN-I-producing DCs [337,338]; conversely, in other models, pDC deficiency exacerbates arthritis, and disease activity improves with pDC mobilization/activation via TLR7 agonists [339,340,341].