Poly I:C–induced expression of IFN-regulated genes but not proinflammatory cytokines is both cell-type and species specific. (A) Human DCs and MØs, (B) murine DCs, (E) ECs, and (E,F) RA-SFs were stimulated with either 100 ng/mL LPS or poly I:C (in μg/mL) as indicated. The supernatants were analyzed for IP-10, IL-6, and TNFα by ELISA. The data are mean values (± SD) from triplicates and are representative of at least 3 experiments using cells of different donors. (C) Human DCs were stimulated with either 100 ng/mL LPS or 20 μg/mL poly I:C, and total RNA was isolated and assessed for the levels of TNFα and IL-6 mRNA by Taqman PCR. The points correspond to values from 4 different donors (± SD). (D) Human DCs were stimulated with 20 μg/mL poly I:C or 100 ng/mL LPS and cocultured with 10⁵ allogeneic T cells in quadruplicate. Proliferation was determined on day 5 using [³H] thymidine. Each point represents the mean (± SEM) from 3 independent experiments on unrelated donors. Human DCs were also examined for cell surface expression of CD80, CD86, HLA-DR, and CD83 by flow cytometry. Unstimulated DCs (black line) and DCs treated with 20 μg/mL poly I:C for 48 hours (gray line) were compared. Cells stained with isotype control (filled histograms) or anti-TLR3 antibody (open black histograms) are shown. One representative of 3 independent experiments is shown.