Poly I:C stimulation is dependent on endosomal maturation in both human dendritic cells and RA synovial fibroblasts. Human DCs and RA-SFs were incubated with chloroquine for 1 hour prior to stimulation with 20 μg/mL poly I:C for 18 hours. The supernatants were analyzed by ELISA. The data are mean values (± SD) from triplicates.