The effects of blocking endogenous activin-A with follistatin on LPS or CD40L-mediated IL-6 production by MoDCs. Immature MoDCs were cultured in 96-well plates for 4 to 24 hours with either GM-CSF and IL-4 alone or with LPS or CD40L in the absence or presence of increasing concentrations of follistatin (A-C). Supernatants were collected at the various times indicated (A) or after 24 hours (B,C) and assayed for IL-6 production by ELISA; 2 × 10⁴ immature MoDCs were cultured in 96-well flat-bottomed plates in media supplemented with GM-CSF and IL-4 and transfected with Alexa Fluor-labeled siRNA or control nontargeted siRNA or targeted activin βA chain siRNA. Efficiency of transfection was measured by flow cytometry (D). Transfected MoDCs were stimulated with 2 μg/mL CD40L for 24 hours, and supernatants were assayed for IL-6 production (E). Data represent the mean plus or minus 1 SD of 3 separate donors, except in panel D where one representative donor is shown and panel E where individual donors are shown. *P ≤ .01, **P ≤ .05 versus CD40L only; †P ≤ .01 versus CD40L stimulated nontargeted siRNA transfected MoDCs.