Poster Presentation CD1-MR1 2024

Innate cytokines license cytotoxic potential of antigen-activated MAIT cells (#201)

Laura Wedlock 1 , Rajesh Lamichhane 1 , James E. Ussher 1 2
  1. University of Otago, Dunedin, New Zealand
  2. Southern Community Laboratories , Dunedin, New Zealand

Mucosal-associated invariant T (MAIT) cells are an abundant innate-like T cell population that express a semi-invariant TCR (Vα7.2-Jα33/12/20)1. MAIT cells respond to a wide range of bacteria through TCR recognition of conserved metabolites, such as 5-(2-oxyopropylideneamino)-6-D-amino-ribityluracil (5-OP-RU), derived from microbial riboflavin synthesis, presented by MHC-class 1b related molecule, MR12,3. Upon activation, MAIT cells rapidly produce pro-inflammatory cytokines (e.g. IFN-γ and TNF-α) and cytotoxic molecules (e.g. granzyme B and perforin) and can directly lyse bacterially infected cells in vitro4,5. Consistently, MAIT cells have been shown to mediate protection against various bacterial infections in vivo6,7. However, the signals that modulate MAIT cell cytotoxic function have not been fully elucidated. Using human PBMCs, we show that type I interferons (T1-IFNs) enhance expression of cytotoxic molecules (granzyme B and perforin) on MAIT cells treated with either 5-OP-RU or IL-12/IL-18, suggesting an important role for T1-IFNs over both TCR and non-TCR signals. RNA-sequencing of MAIT cells activated by 5-OP-RU and/or T1-IFNs highlighted various T1-IFN regulated functions in MAIT cells including cytotoxicity. In line with this, priming of MAIT cells with T1-IFNs further enhanced MAIT cell mediated killing of E. coli-exposed BCLs in our in vitro cytotoxic assay. We have also discovered an innate signal that selectively modulates cytotoxic potential of TCR-activated MAIT cells without influencing the expression of inflammatory cytokines (unlike T1-IFNs). Overall, innate cytokines including T1-IFNs control MAIT cell cytotoxic potential.

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