Ruxolitinib reduces the numbers of activated and LCMV-specific CD8⁺ T cells in LCMV-infected Prf1^−∕− mice. Mice treated with PBS, ruxolitinib, LCMV, and LCMV + ruxolitinib (L+R) were euthanized on day 9 postinfection. Splenocytes were stained using anti-CD4, CD8, CD44 antibodies and fluorochrome-conjugated MHC class I tetramer (D^bgp33). (A) Representative flow cytometric plots showing the percentages of CD4⁺, CD8⁺, CD8⁺CD44⁺ (top and middle panels, gated on live splenocytes) and CD8⁺gp33⁺ (bottom panels, gated on CD8⁺CD44⁺ cells) cells from a representative mouse in each group. (B) Percentage and (C) absolute number of splenic CD8⁺, CD8⁺CD44⁺, and CD8⁺CD44⁺gp33⁺ cells. Data are shown as mean ± SD and are representative of 4 independent experiments. *P < .05.