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. Author manuscript; available in PMC: 2017 Sep 30.
Published in final edited form as: Nitric Oxide. 2016 Jul 4;59:28–41. doi: 10.1016/j.niox.2016.06.009

Figure 1. Schematic overview of Mtb infection.

Figure 1

Mtb infection is initiated when an individual is exposed to aerosolized bacteria. Of those exposed, ~70% remain uninfected, whereas ~30% develop primary infection. The host immune response to the primary infection is initiated by innate immune responses of macrophages and neutrophils via phagocytosis, upregulation of iNOS and HO-1 and production of ROS/RNS. This is followed antigen presentation by dendritic cells, cell-mediated immunity and further infiltration of immune cells. These responses initially restrict bacterial replication and dissemination and lead to the formation of granulomas. In most cases, Mtb resides within the granuloma in a non-replicating dormant state leading to LTBI. Approximately 90% of individuals with LTBI remain asymptomatic while ~5% develop active TB disease, characterized by massive hemoptysis, dysregulated immune responses and extensive tissue damage.