B6.IDO−/− Mice Succumb to MAIDS After LP-BM5 Infection. B6 and B6.IDO−/− mice were infected in parallel, with 5x104 pfu of LP-BM5, and MAIDS parameters were assessed at 8 wpi. (A) Spleen weights. (B) Serum IgG2a and IgM as assessed by ELISA. (C) Emergence of Thy1.2-CD4+ T-cells as assessed by flow cytometry. Percent of Thy1.2+CD4+ of the total CD4+ cell population, calculated from the flow plots of all the experiments. (D) Increase in the CD11b+GR-1+ cell population, assessed by flow cytometry. Percent of CD11b+GR-1+ of total splenocyte population, calculated from the flow plots of all the experiments. (E) Thymidine incorporation after stimulation with ConA and LPS, counts per minute (cpm). Mitogen percent inhibition of the uninfected control to ConA and LPS responses is shown. All histograms represent the mean of samples from four independent experiments, with indicated standard deviations. *p < 0.05; **p < 0.01, ***p < 0.001; **** p < 0.0001, in comparison to uninfected controls, as determined using one-way ANOVA.