Attenuated DC cluster formation and effector T cell activation in the skin by BLT1 blockade. (A) Representative images of the whole-mount staining of ear skin stained with anti–MHC class II mAb 24 h after DNFB application. Mice were treated with vehicle, RvE1, or a BLT1 antagonist 30 min before 0.5% DNFB application. White circles indicate DC cluster formation. Bars, 100 µm. (B) Quantification of DC cluster formation. Scores were assigned according to the size and the number of clusters (n = 4). (C) Number of IFN-γ⁺ CD8⁺ T cells per ear 18 h after 0.3% DNFB elicitation (n = 4). Mice were treated with vehicle, RvE1, a BLT1 antagonist, or RvE1 plus a BLT1 antagonist 30 min before the challenge (n = 3). (D) Ear thickness change at 24 and 48 h after the challenge. Mice were treated with vehicle, RvE1, a BLT1 antagonist, or RvE1 plus a BLT1 antagonist 30 min before the challenge (n = 3). (E) Representative FACS plots of IFN-γ–producing CD8⁺ T cells in the skin 18 h after 0.5% DNFB elicitation. LN cells from DNFB-sensitized WT mice were transferred into WT or BLT1-deficient mice. Recipient mice were challenged with 0.5% DNFB after transfer (n = 4). Numbers in the top right quadrants indicate the percentage of IFN-γ⁺ CD8⁺ T cells in total CD8⁺ cells. (F) Number of IFN-γ⁺ CD8⁺ T cells per ear 18 h after 0.5% DNFB elicitation (n = 4). (G) Ear thickness change at 24 and 48 h after the challenge (n = 3). Results are expressed as the mean ± SEM. All p-values were obtained by Student’s t test: *, P < 0.05. All data are representative of five independent experiments with reproducible results.