Treatment with ruxolitinib improves laboratory features of HLH in LCMV-infected Prf1−∕− mice. (A) Prf1−∕− mice were infected with 2 × 105 PFU LCMV on day 0 (open/white arrow). Starting on day 4, mice were treated or not with ruxolitinib twice daily by oral gavage. Between days 8 and 10, mice were euthanized and analyses performed. (B) Whole-spleen images from treatment groups. (C) Splenomegaly was quantified by measuring the ratio of spleen to body weight × 100. (D) Blood was analyzed for the number of WBCs, RBCs, Hgb, Plt, NCs, and LCs. Data shown are mean ± SD and are representative of 4 independent experiments. *P < .05.