The effect of SLAM signaling on the IL-12, TNF-α, and IL-6 production of DCs activated by CD40L or LPS. DCs were activated with 100 ng/mL LPS and 10 ng/mL IFN-γ in the presence of L cells or L cells expressing the SLAM receptor, as indicated. As previously described, CD40L-induced activation was delivered by CD40L-L cells or SLAM/CD40L-L cells or by the combination of CD40L- and LPS-induced signaling as indicated. (A) The amount of secreted IL-12, TNF-α, and IL-6 was measured by ELISA 24 hours following activation. The result of a representative experiment is shown. Error bars represent the standard deviation of triplicate cultures. (B) Relative expression levels of IL-12p40 mRNA in DCs activated with LPS and IFN-γ in the presence of SLAM-L cells or L-cell control were determined by quantitative RT-PCR. Error bars represent the standard deviation of triplicate RNA samples. (C) The effect of SLAM/SLAM interactions on IL-12, TNF-α, and IL-6 production of activated DCs derived from individual donors. Donors are represented by filled circles and mean values are indicated with horizontal lines. The effect of SLAM is plotted as fold-activation of cytokine production on a logarithmic scale.