Intra-articular CD1c+ myeloid dendritic cells induce strong proliferation of CD4+ T cells associated with a strong increase in proinflammatory T cell cytokine production. (A) Inflammatory myeloid dendritic cells (mDCs) from synovial fluid (SF) when added to autologous CD4+ T cells induced a strong spontaneous proliferation of CD4+ T cells of rheumatoid arthritis (RA) patients (n = 5), significantly higher compared with mDCs from peripheral blood (PB; n = 11). (B) Paired analysis of mDCs from PB and SF from the same donors (n = 3, 10,000 DCs/50,000 CD4+ T cells) showed a similar robust induction of autologous T cell proliferation by SF mDCs. (C) mDCs from SF (n = 5) induced a strong production of proinflammatory cytokines (interferon gamma (IFNγ), interleukin (IL)-17 and IL-4) compared with PB mDCs (n = 11). (D) SF mDC-induced T cell proliferation was strongly dependent on CD80/86 costimulation as it was completely blocked in the presence of CTLA4-Ig. Statistically significant differences of *P <0.05 and **P <0.01. CPM, counts per minute.
Moret et al. Arthritis Research & Therapy 2013 15:R155 doi:10.1186/ar4338