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

Figure 4

Natural killer (NK) cells have the capacity to restrict M. tuberculosis replication through the production of soluble mediators such as GM-CSF, IL-12, TNF-α, IL-22, and IFN-γ. These upregulate the antimicrobial function of infected macrophages and activate antigen-specific T cell responses during M. tuberculosis infection. NK cell-derived antimicrobial factors such as granulysin and perforin indirectly restrict Mtb growth via the lysis of infected host cells. Several studies suggest that NK cells directly recognize Mtb-derived mycolic acids via NKp44. Aside from direct recognition of Mtb ligands, NKp30 and NKp46 recognize a variety of stress molecules upregulated on the surface of infected host cells.