Granulysin Antimicrobial Activity Promotes Dormancy in Mycobacterium tuberculosis

Area of Science:

• Immunology
• Microbiology
• Pathogenesis

Background:

• Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), is a major global health issue.
• Granulomas are key structures in TB pathogenesis, influencing infection outcomes.
• Mtb persists in a dormant, antibiotic-tolerant state within granulomas, evading immune responses.

Purpose of the Study:

• To identify immune factors within granulomas that drive Mtb dormancy.
• To elucidate the mechanisms by which Mtb persists within the host.

Main Methods:

• Generation of ex vivo granuloma-like structures from TB patient peripheral blood mononuclear cells.
• High-dimensional mass cytometry to analyze immune cell populations and functions.
• Direct exposure of Mtb to granulysin to assess dormancy induction.

Main Results:

• Patient-derived granuloma-like structures induced Mtb dormancy ex vivo.
• This dormancy correlated with an enrichment of activated innate cytotoxic lymphocytes.
• CD56+ lymphocytes and their granule contents, particularly granulysin, were essential for inducing Mtb dormancy.

Conclusions:

• Granulysin, released by CD56+ lymphocytes, directly induces Mtb dormancy.
• This represents an immune escape mechanism where Mtb enters a dormant state to evade cytotoxic lymphocyte activity.