Ruxolitinib (Ruxo) reduces CD8⁺ T-cell cytokine production in primary HLH. (A) Representative flow cytometric plots of intracellular IFN-γ and TNF-α produced by splenic CD8⁺ T cells after in vitro stimulation with LCMV-restricted gp33 peptide. Depicted on the right are summarized frequency (upper panels) and absolute numbers (lower panels) of TNF-α⁻IFN-γ⁺ and TNF-α⁺IFN-γ⁺ CD8⁺ T cells. (B) Mean fluorescence intensity (MFI) of IFN-γ in CD8⁺ T cells (left panel) and representative graphs (right panel). (C) MFI of TNF-α in CD8⁺ T cells (left panel) and representative graphs (right panel). Each data point represents 1 mouse. Data (mean ± standard deviation) are representative of 2 independent experiments (n = 5 mice per group). *P < .05, **P < .01, ***P < .001, ****P < .0001.