Persistence and strength of stimuli modulate MoDC cytokine secretion. MoDCs were stimulated as in the legend to Figure 3. DC cultures were washed twice 3 hours and 12 hours after addition of the indicated stimuli, supernatants were analyzed for IL-12p70 and IL-6, and cultures continued in RPMI plus 10% FCS without cytokines for a further 36 to 48 hours. Cultures containing the various stimuli throughout the 36-hour culture period were run in parallel as controls. Secretion of (A) IL-12p70 and (B) IL-6 by MoDCs stimulated either transiently or continuously with CD40L₁ plus IFN-γ or (C) IL-12p70 secretion following transient or continuous stimulation with CD40L₃ plus IFN-γ (mean ± SEM of 6 to 9 experiments, *P < .05; **P < .01 as compared with 36-hour to 48-hour stimulation). (D) IL-12p70 or (E) IL-6 secretion of MoDCs stimulated once or repeatedly (0, 6, 18 hours) with CD40L₁ plus IFN-γ (mean ± SD of 4 experiments, *P < .05 as compared with single stimulation). Effect of titrating CD40L₃ in the presence of 1000 U/mL IFN-γ on (F) migration toward CCL21 and (G) IL-12p70 secretion (mean ± SEM of 9 experiments, *P < .05 as compared with 2 μg/mL CD40L₃).