JAK1 inhibition is not sufficient to reduce CD8 T-cell number or capacity to produce IFN-γ. Proportions and numbers of total splenic CD8 T cells (A), CD44⁺ effector CD8 T cells (B), and gp33-specific CD8 T cells (C) in naïve mice or LCMV-infected Prf1^−/− mice treated with vehicle, itacitinib (120 mg/kg), fedratinib (60 mg/kg), or ruxolitinib (90 mg/kg) from days 4 to 8 PI. Analysis was performed on day 9 PI. (D-E) Representative contour plots and summary data of cytokine producing CD44⁺ CD8 T cells (D-E) and gp33⁺ CD8 T cells (F-G) after in vitro restimulation with gp33 peptide. Data points represent single mice from 5 pooled experiments. ∗P < .05, ∗∗P < .01, or ∗∗∗∗P < .0001 by pairwise comparison.