Simultaneous stimulation of both DC populations with limited amounts of TLR agonists leads to synergistic activation. (A) Percentage of CD40⁺ pDCs (○) and mDCs (□) was cultured in isolation or together (● and ■, respectively). Cultures were treated with the indicated concentrations of the TLR7/8 agonists R848 (left panel) or Pam₃CSK₄ (right panel), a TLR2 agonist. A representative experiment of 3 is shown. (B) Percentages of CD40⁺ mDCs (left panel) and pDCs (right panel) cultured in isolation (squares) or together (circles) in presence of the indicated concentration of LPS and CpG (filled symbols). A representative experiment of 3 is shown. (C) Measurement of IP-10 secretion by pDCs and mDCs cultured in isolation or together at the indicated concentration of LPS. CpG was added (■) or not (□) to the cultures, and the effects on IP-10 production are shown. The data are from a representative experiment of 3 performed.