MAIT cells in bacterial infectious diseases: heroes, villains, or both?

Abstract

Due to the aggravation of bacterial drug resistance and the lag in the development of new antibiotics, it is crucial to develop novel therapeutic regimens for bacterial infectious diseases. Currently, immunotherapy is a promising regimen for the treatment of infectious diseases. Mucosal-associated invariant T (MAIT) cells, a subpopulation of innate-like T cells, are abundant in humans and can mount a rapid immune response to pathogens, thus becoming a potential target of immunotherapy for infectious diseases. At the site of infection, activated MAIT cells perform complex biological functions by secreting a variety of cytokines and cytotoxic substances. Many studies have shown that MAIT cells have immunoprotective effects because they can bridge innate and adaptive immune responses, leading to bacterial clearance, tissue repair, and homeostasis maintenance. MAIT cells also participate in cytokine storm generation, tissue fibrosis, and cancer progression, indicating that they play a role in immunopathology. In this article, we review recent studies of MAIT cells, discuss their dual roles in bacterial infectious diseases and provide some promising MAIT cell-targeting strategies for the treatment of bacterial infectious diseases.

Keywords: MAIT cells; bacterial infectious disease; immunopathology; immunoprotection; immunotherapy.

Figure 1.

Mucosal-associated invariant T (MAIT) cells in bacterial infectious diseases. In bacterial infectious diseases, pathogens or riboflavin metabolisms are captured by antigen-presenting cells (APCs), which can activate MAIT cells in a TCR-dependent manner or cytokine (CK)-dependent manner. Upon activation, MAIT cells proliferate, secrete abundant cytokines, and then recruit and activate other immune cells, acting as a bridge to link innate and adaptive immunity. Activated MAIT cells act as heroes, villains, or both in different bacterial infectious diseases.