Poly heterozygous mice for HLH-causing genes display biological features of HLH upon LCMV infection. Control (black bars), Prf1^−/− (lightest gray bars), Rab27a^+/−Stx11^+/− (AS, light gray bars), Rab27a^+/−Prf1^+/− (AP, medium gray bars), and Rab27a^+/−Prf1^+/−Stx11^+/− mice (ASP, dark gray bars) were infected with 200 PFU of LCMV-WE. (A) WBC counts, (B) RBC counts, (C) hematocrit, (D) Hb, and (E) platelets counts were monitored 14 and 21 days postinfection. Data (mean ± SEM) are representative of 3 to 4 independent experiments with at least 3 mice in each group. Dashed lines represent normal values for mice. *P < .05; **P < .01; ***P < .001; ****P < .0001. Hct, hematocrit; PTL, platelets.