Silencing DC expression of CD40 in vitro by CD40 siILs. (A) Gene silencing of CD40 siRNA. Day 6 BMDCs were transfected with CD40 siRNA, or negative control siRNA, complexed with GP transfection reagent. Cells were activated with LPS on day 7 and assayed for protein expression and CD40 mRNA by (A) flow cytometry and (B) quantitative PCR. (C) In vitro silencing of CD40 expression in BMDC using siIL-encapsulated CD40 siRNA. On day 6 of culture, BMDCs were transfected with increasing amounts of siIL-encapsulated CD40 siRNA, siIL-encapsulated negative control (nonspecific) siRNA, or PBS. DCs were activated with LPS on day 7, and CD40 protein expression was measured by flow cytometry on day 8. Data presented are representative of 3 independent experiments (*P < .05).