Rat and human DCs express functional HO-1. (A) Western blot analysis of HO-1 expression in rat freshly isolated splenic OX62⁺ DCs, freshly isolated plasmacytoid dendritic cells (pDCs), and BMDCs cultured for 8 days was performed using an anti-HO-1 antibody. Purified splenic B cells were used as a negative control. An anti-β tubulin antibody was used as a loading control. (B) Confocal micrographs show rat HO-1⁺ cells (green fluorescence); CD4⁺, CD45RB⁺, or MHC class II⁺ cells (red fluorescence); and merged images with dual labeling. Cell nuclei were counterstained with TO-PRO-3 (blue; objective, × 63/1.4). (C) Rat immature bone marrow-derived DCs express functional HO-1 as shown by the presence of HO-1⁺ cells (green fluorescence) also reactive with an antibilirubin mAb (red fluorescence). Merged images display dual labeling. Cell nuclei were counterstained with TO-PRO-3 (blue; objective, × 63/1.4). (D) Human immature monocyte-derived DCs express functional HO-1 as shown by the presence of HO-1⁺ cells (green fluorescence) also reactive with an antibilirubin mAb (red fluorescence). Merged images display dual labeling. Cell nuclei were counterstained with TO-PRO-3 (blue; objective, × 63/1.4). Similar results were obtained for each DC cell type in 2 to 5 independent experiments.