Cytokine release and phenotypic changes following pDC exposure to TLR agonst. Synovial fluid (SF) plasmacytoid dendritic cells (pDCs) mature and release interferon alpha (IFN-α) and tumour necrosis factor alpha (TNF-α) at comparable levels with healthy control peripheral blood (PB) pDCs, but only SF pDCs release IL-10. Cytokine release and the maturation status of pDCs purified from healthy control PB (n = 3) and inflammatory arthritis SF (rheumatoid arthritis, n = 2; psoriatic arthritis, n = 1) were assessed after 24-hour incubation with IL-3-supplemented media alone or containing the TLR9 agonist CpG ODN 2216 (3.2 μg/ml). (a) The concentrations of IFN-α, TNF-α and IL-10 in supernatant from cultures was determined by multiplex and ELISA analysis, and was expressed as release per 5 × 104 cells. Squares indicate individual donors. (b) Maturation and co-stimulation marker expression was determined by flow cytometry, and one representative example from each of the healthy control PB and inflammatory arthritis SF groups are shown.