IL-21 Selectively Augments Cytotoxic Potential of Antigen-Activated MAIT Cells

Area of Science:

• Immunology
• Cell Biology
• Microbiology

Background:

• Mucosal-associated invariant T (MAIT) cells are unconventional T cells recognizing microbial metabolites via MR1.
• MAIT cell activation occurs through T cell receptor (TCR) engagement or cytokine signaling (IL-12/IL-18).
• Upon activation, MAIT cells release cytotoxic molecules like granzyme B and perforin to eliminate infected cells, but the role of cytokines in regulating this cytotoxicity is unclear.

Purpose of the Study:

• To investigate the specific role of the cytokine Interleukin-21 (IL-21) in regulating MAIT cell cytotoxicity.
• To determine if IL-21 influences the expression of cytotoxic molecules and the killing capacity of MAIT cells.

Main Methods:

• MAIT cells were activated via TCR or IL-12/IL-18 signaling.
• The effect of IL-21 priming on MAIT cell granzyme B and perforin expression was assessed.
• A flow cytometry-based cytotoxic assay was employed to measure MAIT cell killing of target cells (5-OP-RU-treated B cell lines).

Main Results:

• IL-21 significantly enhanced the expression of granzyme B and perforin in TCR- or IL-12/IL-18-activated MAIT cells.
• IL-21 had a minimal impact on MAIT cell cytokine production.
• Priming with IL-21 improved the cytotoxic activity of MAIT cells against bacterial antigen-presenting cells.

Conclusions:

• IL-21 acts as a co-stimulatory molecule that selectively augments the cytotoxic potential of MAIT cells.
• This finding highlights a novel role for IL-21 in enhancing MAIT cell-mediated immunity against microbial infections.