Ruxolitinib impairs the T-cell stimulatory function of DCs in vivo. (A) Mice were fed twice via oral gavage either ruxolitinib (▪) or vehicle (□) prior to and after injection of OVA/CpG, followed by an analysis of MHC expression and activation markers on CD11c⁺CD8⁺ splenic DCs 20 hours after priming. Gray columns represent mice vaccinated with OVA/CpG without receiving vehicle or ruxolitinib feeding, to exclude any effects of the oral gavage per se. (B-G) CFSE-labeled OT-I cells (2 × 10⁶) were adoptively transferred to naive C57/BL6N recipient mice injected with OVA/CpG. Mice were fed 6 hours prior to as well as 6 and 18 hours after priming with OVA/CpG with ruxolitinib (gray shaded) or its vehicle (black line). (B) OT-I cell proliferation shown as histogram and (C) division index as well as (D-E) CD25 expression and (F-G) IFN-γ production (analyzed by intracellular cytokine staining) were assessed 2.5 days after priming with OVA/CpG. (H) Using the entirely endogenous T-cell repertoire of nontransgenic C57/B6N mice primed with OVA/CpG, OVA-specific cytotoxicity on day 5 was assessed. Mice had been treated either with ruxolitinib or its vehicle in the concentrations and schedule indicated above. Results are from 1 experiment (n = 4 per group) representative of at least 3. The significance was calculated according to (A) the 1-way ANOVA Dunnett multiple comparison test or (C,E,G,H) Mann-Whitney test and is always related to the vehicle control. *P < .1; **P < .01.