STAT1, but not STAT4, is required for IFN-α/β inhibition of IL-12p70 production by DCs. (A) Wild-type C57BL/6 or pDC-depleted mice were challenged with 4 × 105 PFU/mL salivary-gland prepared MCMV Smith strain. pDC-depleted mice were generated using anti–Gr-1 antibody (clone RB6-8C5) as described in “Material and methods.” pDC depletion was confirmed by FACS analysis on splenocytes of treated mice (data not shown). Serum samples at 36 hours after MCMV challenge were analyzed for IFN-α production by ELISA. (B-D) IFNAR−/−, STAT1−/−, or STAT4−/− mice and their respective controls (C57BL/6, 129SVE, and Balb/c) were challenged with MCMV. At 36 hours after infection, spleens were harvested and stained with CD8-FITC, CD11c-PE, and anti–IL-12–APC as described in “Materials and methods.” The percentage of CD11c+ DCs that stained positively for IL-12 is expressed as bar graph.
