The impact of defined dsRNA motifs on innate immunity and APCs. (a) The chemokine expression triggered by 50 μg pA:pU (black bars) or pI:pC (white bars) dsRNA was compared with that induced by 1 μg of LPS (gray bars) 24 hours after mucosal administration. The chemokines that bind to receptors on Th1 and Th2 cells are indicated with solid or dashed lines. (b) Recruitment of professional APCs in the lungs of mice treated with dsRNA motifs was assessed by FACS. Results are expressed as number of CD11c⁺ (black bars) and CD11b⁺ (white bars) cells separated from the pulmonary interstitial tissue (n = 4/group). (c) Activation of professional APCs by the dsRNA motifs was ascertained by ex vivo overnight pulsing of CD11c⁺ cells with antigen (100 μg/ml of IgHA) together with 50 μg/ml of dsRNA, followed by adoptive transfer of APCs into naive mice. As controls, we used antigen-pulsed APCs or costimulated with either recombinant IL-12 or anti-CD40 mAb. Results are expressed as number of IL-2⁺ SFCs measured in the spleen. (d) Cross-priming was studied in BALB/c mice immunized with gp140 antigen together or without pA:pU. The response was measured by ELISpot analysis using the peptide R10K. Results are expressed as mean ± SEM of the number of IFN-γ⁺ (black bars) and IL-4 (white bars) SFCs/spleen (n = 4/group). (e) Cross-priming was studied in C57BL/6 mice treated with 100 μg of whole OVA together with or without pA:pU, by ELISpot analysis using in vitro stimulation with the peptide SIINFEKL. Results are expressed in d.