MAIT cells detect and efficiently lyse bacterially-infected epithelial cells

Area of Science:

• Immunology
• Microbiology
• Cell Biology

Background:

• Mucosal associated invariant T cells (MAIT) are innate T lymphocytes recognizing microbial compounds.
• This recognition is mediated by the Major Histocompatibility Complex (MHC) class I molecule, MR1.
• MAIT cells play a role in host defense against microbial infections.

Purpose of the Study:

• To investigate the cytotoxic activity of MAIT cells against bacteria-infected cells.
• To explore the role of the NK receptor CD161 in MAIT cell responses.
• To assess MAIT cell activation in response to bacterial infection and vaccination in humans.

Main Methods:

• Coculture assays of MAIT cells with MR1-overexpressing non-hematopoietic cells and bacteria.
• Analysis of MAIT cell responses (cytokine production, cytotoxicity) upon interaction with infected cells.
• In vivo study of MAIT cell activation in human volunteers receiving a Shigella vaccine.

Main Results:

• MAIT cells exhibit cytotoxic activity against MR1-overexpressing cells infected with bacteria.
• CD161 modulates cytokine but not cytotoxic responses of MAIT cells to infected cells.
• MAIT cells are activated by and kill epithelial cells infected with Shigella flexneri but not Salmonella Typhimurium.
• MAIT cells are activated in humans receiving a Shigella dysenteriae vaccine.

Conclusions:

• MAIT cells are a major T cell subset in humans capable of detecting and killing bacteria-infected cells.
• MAIT cell responses are specific to certain bacterial species and infection contexts.
• MAIT cells represent a potential target for immunotherapies and vaccine development.