Although IL-4i1 mRNA expression was significantly up-regulated in the lungs of WT mice 3 weeks after infection, compared with naive mice (Supplementary Figure 3D), the mRNA levels of other immunosuppressive metabolic enzymes, indoleamine 2,3-dioxygenase 1 and 2, remained unchanged in the lungs of WT and IL-4i1−/− mice 3 weeks after HN878 Mtb infection (Supplementary Figure 3E). This evidence concerns the gene IDO1 and infection.