To distinguish whether the reduced inflammatory response in Cbs+/− mice during chronic infection is due to lower CBS protein levels or reduced bacillary burden, we analyzed the immune response at an early time after infection (3 weeks) when the lung bacillary burden was similar (Supplementary Fig. 4A), but serum sulfide levels differed between WT, and Cbs+/− mice (Supplementary Fig. 4B). Here, CBS is linked to infection.