Hate-buffered saline (PBS, without calcium and magnesium, pH 7.4, and prewarmed at

Hate-buffered saline (PBS, without calcium and magnesium, pH 7.4, and prewarmed at 37uC). The uid was infused, recovered and placed immediately on ice. The BALF wasImportance of Type I IFN and FasL in InfluenzaFigure 2. Virus titer in the lungs of mice does not correlate with the AZP-531 chemical information severity 1081537 of the influenza infection. B6 mice (5 mice/group) were infected with 105 (closed triangle) or 102 (open square) pfu/head of the PR/8 virus. Changes in body weight (A) or survival rate (B) of these mice were shown. At the indicated days after the infection, the virus titer in the lungs of mice infected with 105 (closed) or 102 (open) pfu/head of PR/8 virus was assessed by plaque assay (C, N = 3/each time point). doi:10.1371/journal.pone.0055321.ghuman IgG (Fas-Fc) protected B6 mice against lethal infection of PR/8 virus in a dose dependent manner (Fig. 1B). These findings suggested that the signal mediated by the interaction of FasL with Fas is critical to determine the survival rate of mice lethally infected with the PR/8 virus.Expression of FasL but not Fas Gene in the Lung Correlates with the Severity of Illness in Mice after Influenza A Virus InfectionIt is known that the initial infected titer of the virus regulates the severity of illness such as loss of body weight and death of mice after influenza A virus infection. In B6 mice, infection with a high titer (105 pfu/head i.n.) of PR/8 virus dramatically decreased the body weight of mice at 2,5DPI (Fig. 2A, closed triangle) and all mice were dead at 8 DPI (Fig. 2B, closed triangle). On the contrary, in the mice infected with a low titer of the virus (102 pfu/ head, i.n.), reduction of body weight was slightly observed at 5,6 DPI, and all these mice survived until 19 DPI (Fig. 2A and B, open square). By plaque assay, at 1DPI, the virus titer in the lungs of mice infected with a high titer was shown to be significantly higher, but was lower compared to that with a low titer of the virusafter 2DPI (Fig. 2C). As shown in a previous report [6], these findings suggested that the initial infected but not propagated virus titer in the lungs of mice correlate with the severity of symptoms or mortality of mice after influenza A virus infection. To clarify the correlation of the function of Fas or FasL gene with the severity of illness in this model, their expression in the lungs of these mice were assessed by quantitative real time PCR (QPCR) methods using AZP-531 web specific primer sets for these genes. In a high virus titer infection (lethal condition, 105 pfu/head i.n.), a very high expression of FasL gene was observed at 2DPI and this expression level was sustained until the mice died (Fig. 3A). Compared with FasL gene, expression level of Fas gene was slightly increased during the infection (Fig. 3B). In a low virus titer infection (non-lethal condition, 102 pfu/head i.n.), induction of FasL gene expression was observed after 4DPI (Fig. 3C) and Fas gene expression was not changed (Fig. 3D). It has been demonstrated that the induction level of FasL gene expression is correlated with body weight loss in both lethal and non-lethal conditions (compared with Fig. 3A versus 3E, and Fig. 3C versus 3F). These findings suggested that the gene expression level of FasLImportance of Type I IFN and FasL in InfluenzaFigure 3. Induction of FasL gene in the lungs of mice infected with the PR/8 virus. B6 mice were infected with the PR/8 virus at the indicated virus titer. These mice were sacrificed at the indicated day, and mRNA.Hate-buffered saline (PBS, without calcium and magnesium, pH 7.4, and prewarmed at 37uC). The uid was infused, recovered and placed immediately on ice. The BALF wasImportance of Type I IFN and FasL in InfluenzaFigure 2. Virus titer in the lungs of mice does not correlate with the severity 1081537 of the influenza infection. B6 mice (5 mice/group) were infected with 105 (closed triangle) or 102 (open square) pfu/head of the PR/8 virus. Changes in body weight (A) or survival rate (B) of these mice were shown. At the indicated days after the infection, the virus titer in the lungs of mice infected with 105 (closed) or 102 (open) pfu/head of PR/8 virus was assessed by plaque assay (C, N = 3/each time point). doi:10.1371/journal.pone.0055321.ghuman IgG (Fas-Fc) protected B6 mice against lethal infection of PR/8 virus in a dose dependent manner (Fig. 1B). These findings suggested that the signal mediated by the interaction of FasL with Fas is critical to determine the survival rate of mice lethally infected with the PR/8 virus.Expression of FasL but not Fas Gene in the Lung Correlates with the Severity of Illness in Mice after Influenza A Virus InfectionIt is known that the initial infected titer of the virus regulates the severity of illness such as loss of body weight and death of mice after influenza A virus infection. In B6 mice, infection with a high titer (105 pfu/head i.n.) of PR/8 virus dramatically decreased the body weight of mice at 2,5DPI (Fig. 2A, closed triangle) and all mice were dead at 8 DPI (Fig. 2B, closed triangle). On the contrary, in the mice infected with a low titer of the virus (102 pfu/ head, i.n.), reduction of body weight was slightly observed at 5,6 DPI, and all these mice survived until 19 DPI (Fig. 2A and B, open square). By plaque assay, at 1DPI, the virus titer in the lungs of mice infected with a high titer was shown to be significantly higher, but was lower compared to that with a low titer of the virusafter 2DPI (Fig. 2C). As shown in a previous report [6], these findings suggested that the initial infected but not propagated virus titer in the lungs of mice correlate with the severity of symptoms or mortality of mice after influenza A virus infection. To clarify the correlation of the function of Fas or FasL gene with the severity of illness in this model, their expression in the lungs of these mice were assessed by quantitative real time PCR (QPCR) methods using specific primer sets for these genes. In a high virus titer infection (lethal condition, 105 pfu/head i.n.), a very high expression of FasL gene was observed at 2DPI and this expression level was sustained until the mice died (Fig. 3A). Compared with FasL gene, expression level of Fas gene was slightly increased during the infection (Fig. 3B). In a low virus titer infection (non-lethal condition, 102 pfu/head i.n.), induction of FasL gene expression was observed after 4DPI (Fig. 3C) and Fas gene expression was not changed (Fig. 3D). It has been demonstrated that the induction level of FasL gene expression is correlated with body weight loss in both lethal and non-lethal conditions (compared with Fig. 3A versus 3E, and Fig. 3C versus 3F). These findings suggested that the gene expression level of FasLImportance of Type I IFN and FasL in InfluenzaFigure 3. Induction of FasL gene in the lungs of mice infected with the PR/8 virus. B6 mice were infected with the PR/8 virus at the indicated virus titer. These mice were sacrificed at the indicated day, and mRNA.