Platelets and platelet-TLR7 mediate infection-affected mortality. WT male mice (17 weeks) were depleted of platelets by injecting anti-GPIb-α antibody (2 μg/g of mouse), and at 12 hours postinjection they were infected with EMCV. (A) Survival of EMCV-infected, platelet-depleted mice (n = 13) compared with IgG-injected and infected controls (n = 12) evaluated by Mantel-Cox test. Noninfected anti-IgG (n = 4) or anti-Plt (n = 4) injected mice had a 100% survival. (B-F) Platelets from WT or TLR7KO mice (abbreviated KO here) were isolated, labeled with CFSE, and transfused in recipient mice (all mice had similar CFSE-labeled platelets posttransfusion assessed by flow cytometry) as labeled on the graphs. The control mice were transfused with buffer in which platelets were concentrated. Mice were injected with EMCV 2 hours posttransfusion. (B-C) Survival curves of the injected mice determined by Mantel-Cox test and based on: n = 5 for WT->KO and n = 6 for buffer->KO, and n = 6 for KO->WT and n = 5 for buffer->WT. (D) Reduction in platelet count in the transfused KO (see Figure 1F) mice as a result of platelet-TLR7 presence. (E) Platelet count in the WT mice as a result of KO platelet transfusion. (F) Heterotypic aggregates induced in the WT and the KO mice post buffer transfusion. Data for D-F are average ± SD and were analyzed by 2-tail Student t test, based on the following n: (D-E) n = 4 (WTplt->KO), n = 5 (buffer->KO), n = 5 (KOplt->WT), and n = 3 (buffer->WT) (F) WT groups: n = 3 (control), n = 3 (EMCV), n = 3 (control), and n = 5 (EMCV).