biostudies-literatureUnknown28(7)Decker AHHealth~HollandRadboudumcInflammatory arthritis (IA) is characterized by persistent joint inflammation and immune cell infiltration, including CD1c⁺ dendritic cells (DCs), comprising DC2s and DC3s. To investigate their developmental and functional specialization in IA, we characterized DC2s and DC3s in the peripheral blood (PB) and synovial fluid (SF) of patients with IA. DC3 frequencies were increased in PB of patients with juvenile idiopathic arthritis and correlated with disease activity in early rheumatoid arthritis. While PB DC3s showed strongly impaired T cell activation, SF DC3s induced only marginally lower T cell proliferation compared to DC2s and primed higher frequencies of IL-17⁺ and IFN γ ⁺ T cells. Furthermore, SF from patients with IA induced the DC3 phenotype in DC2iScience112957https://www.ebi.ac.uk/biostudies/studies/S-EPMC12270937biostudies-literatureInterleukin-6 in synovial fluid drives the conversion of DC2s to DC3s in inflammatory arthritis.PMC12270937Thurlings RMBoks MAPopa CDVerdoes MThomas Rde Vries IJMSanchez-Rocha LDecker AHBakdash Gvan den Hoogen LLvan Oorschot TBecker AMDfalseInterleukin-6 in synovial fluid drives the conversion of DC2s to DC3s in inflammatory arthritis.Inflammatory arthritis (IA) is characterized by persistent joint inflammation and immune cell infiltration, including CD1c⁺ dendritic cells (DCs), comprising DC2s and DC3s. To investigate their developmental and functional specialization in IA, we characterized DC2s and DC3s in the peripheral blood (PB) and synovial fluid (SF) of patients with IA. DC3 frequencies were increased in PB of patients with juvenile idiopathic arthritis and correlated with disease activity in early rheumatoid arthritis. While PB DC3s showed strongly impaired T cell activation, SF DC3s induced only marginally lower T cell proliferation compared to DC2s and primed higher frequencies of IL-17⁺ and IFN γ ⁺ T cells. Furthermore, SF from patients with IA induced the DC3 phenotype in DC22025-01-01T00:00:00Z2025 Jul2026-03-18T14:14:20.885Z2025-08-24T03:05:34.444ZS-EPMC122709374068778410.1016/j.isci.2025.112957