Ruxolitinib therapy improves clinical and hematological parameters of HLH in Prf1^−/− mice. (A) Body weight (left) and body temperature (right) of B6 and Prf1^−/− mice infected at day 0 and receiving ruxolitinib treatment or not during 14 days, or anti- IFN-γ antibody every third day, from day 7 until day 16, and then followed up to day 28 (upper) or receiving ruxolitinib treatment during 21 days and followed up to day 55 (lower). *P < .05; **P < .005. (B) Hematological parameters (white blood cells [WBC], platelets [PLT], red blood cells [RBCs], and hematocrit [Hct]) at different times (days 0-28 postinfection) of nontreated control (B6) mice and Prf1^−/− mice nontreated, treated with ruxolitinib from day 7 postinfection for 14 days, or treated with anti-IFN-γ antibody from day 7 until day 16. Dotted lines represent normal values. Data (mean ± SEM) are representative of 2 to 4 independent experiments with at least 3 mice in each group. *P < .05; **P < .005.