Neutrophilic inflammation reprograms the bone marrow to impair T cell immunity during Tuberculosis

Abstract

Mycobacterium tuberculosis (Mtb) infection induces persistent influx of neutrophils that precludes both CD4 and CD8 T cells from tuberculosis (TB) lesions in genetically susceptible mice. Depletion of neutrophils restores T cell number and ameliorated disease. High neutrophil to T lymphocyte ratio in the peripheral blood of pulmonary TB (PTB) patients correlate with sputum smear positivity and disease severity. These observations led us to hypothesize that infiltration of neutrophils negatively affect the normally protective T cell response in TB lesions. By employing various mouse strains that present neutrophil-rich lung lesions, we demonstrated that instead of serving as canonical myeloid derived suppressor cells (MDSCs), neutrophils produce granulocyte colony stimulating factor (CSF3/G-CSF) to indirectly regulate T cell numbers in TB lesions. Neutrophil-derived G-CSF reprograms the bone marrow towards a granulocyte-biased hematopoiesis at the expense of lymphocyte progenitors. Transcriptome profiling of the isolated neutrophils from the lung, spleen and bone marrow revealed a type I interferon (IFN-I) response signature in these neutrophils. Hematopoietic cell-intrinsic IFN-I signaling (IFNAR1) is both necessary and sufficient to promote the pathologic granulopoiesis generating Mtb-permissive neutrophils while suppressing lymphocyte progenitors (CLPs) production. Finally, blockade of IFNAR1-signaling ameliorates disease pathology by preserving the hematopoietic equilibrium. Collectively, our work uncovers a mechanism by which type I IFN response in neutrophils along with G-CSF perturbs hematopoiesis in the bone marrow and negatively impacts T cell immunity in TB lesions.