Impaired IFNγ responsiveness of monocyte-derived lung cells limits immunity to Mycobacterium tuberculosis

Abstract

Lung mononuclear phagocyte (MNP) subsets differ in their ability to restrict Mycobacterium tuberculosis (Mtb) during chronic infection, yet the mechanisms underlying this difference are not well defined. Here, we show that CD11clo monocyte-derived cells (MNC1), the subset of lung cells that is most permissive for Mtb viability during chronic infection, express lower levels of interferon-gamma (IFN{gamma}) signaling proteins, resulting in reduced responses to IFN{gamma} compared to alveolar macrophages (AM) and CD11chi MNC2. Moreover, type I IFN signaling suppresses IFN{gamma}-mediated MHC-II expression, impairing antigen-specific CD4 T cell activation by MNC1 cells. Importantly, prior immunity conferred by contained Mtb infection enhances IFN{gamma} responsiveness of monocyte-derived cells, reducing bacterial burdens in lungs and within MNC subsets. Our findings indicate that heterogeneous IFN{gamma} responsiveness is exploited by Mtb for persistence in vivo. Overcoming or bypassing impaired IFN{gamma} responsiveness may guide the development of more effective TB vaccines and host-directed therapies.