Activation of murine dendritic cells by RNA fromA fumigatusconidia or hyphae. (A) Expression of MHC class II antigen and costimulatory molecule on splenic dendritic cells (DCs) transfected with RNA from conidia or hyphae of Aspergillus for 2 hours at 37°C before wash. FACS analysis was done 22 hours later. Black histograms indicate control cells stained with an unrelated mAb. For comparison, LPS-matured DCs were also assessed. None indicates untransfected DCs. (B) Frequency of cytokine-producing cells on DCs either transfected with fungal RNA or pulsed with viable conidia or hyphae. DCs were exposed to viable fungi for 2 hours at 37°C, before the addition of amphotericin B to prevent the fungal overgrowth, and left for an additional 22 hours before ELISPOT assay. None indicates unpulsed cells. ^*P < .05 (pulsed versus unpulsed DCs). (C) Proliferative response of allogeneic CD4⁺ splenic T cells after 5 days of coculture at 37°C with graded numbers of DCs transfected with conidial or fungal RNA. CFSE staining was done as described in “Materials and methods.” Shown are the results from one representative experiment of 3. The number refers to the median fluorescence intensity of T cells unstimulated (black histograms) or stimulated with 10² (red lines), 10³ (blue lines), 10⁴ (yellow lines), and 10⁵ (green lines) DCs.