IDO is Undetectable in B6.IDO−/− Mice Following LP-BM5 Infection. (A) Genomic DNA was isolated from B6 and B6.IDO−/− mice, and the IDO genotypes were determined using PCR. Expected IDO band lengths: w.t. IDO (427 bp) and knockout IDO (280 bp). (B) Relative expression of IDO splenic mRNA by qRT-PCR, as compared to β-actin. Lines represent the mean, n = 10, from three independent experiments. IDO mRNA was not detected (ND) in uninfected or infected B6.IDO−/− mice. **p < 0.01, in comparison to uninfected controls, as determined using one-way ANOVA.