This elegant study further demonstrated eight representative microenvironments within the TB granulomas including features of local immunosuppression, such as high expression of the inhibitory enzyme IDO-1 and the immune checkpoint molecule PD-L1 on myeloid cells, but also proliferative Treg cells and high levels of TGF-β in the absence of IFN-γ (143). Here, IDO1 is linked to tuberculosis.