Innate Immune Defenses in Human Tuberculosis: An Overview of the Interactions between Mycobacterium tuberculosis and Innate Immune Cells

Figure 2

Neutrophils constitute a major subset of innate immune cells in the BAL and sputum of patients with active pulmonary TB. During infection with M. tuberculosis, neutrophils produce and secrete a variety of antimicrobial enzymes to restrict bacterial growth within infected macrophages. These neutrophil effectors promote apoptosis of infected macrophages, thereby limiting Mtb survival within infected host cells. However, these enzymes also mediate lung tissue damage and sustained, hyperactivated inflammatory response. Furthermore, transcriptional profiling studies have demonstrated the importance of PD-L1, a cell-surface associated molecule, in modulating T cell responses during infection with Mtb. Additional transcriptional studies have identified a blood based IFN-inducible gene signature in neutrophils that is unique to tuberculosis-specific immune responses.