C3a-C3aR interaction is required for DC activation. (A,B) Flow cytometric analysis of expression of MHC and costimulatory molecules on cultured 7-day BM DCs that include C3aR^−/− DCs and WT control DCs (A) and C3aRa treated and untreated WT DCs (B). A representative of 3 independent experiments is shown. (C,D) DC cytokine production in response to LPS stimulation. The purified 6-day BM DCs (10⁶/mL), including C3aR^−/− DCs and their WT control DCs (C), and C3aRa treated and untreated WT DCs (D), were further cultured for 24 hours in the presence of LPS. The supernatants were analyzed for IL-12 and IL-10 production using ELISA. Data are means plus or minus SEM (n = 4). Data were analyzed by Student t test (**P < .004). A representative of 5 independent experiments is shown.