MicroRNA-155 Regulates MAIT1 and MAIT17 Cell Differentiation

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• Mucosal-associated invariant T (MAIT) cells are innate-like T cells crucial for immune responses.
• MAIT cells differentiate into MAIT1 and MAIT17 subsets, releasing cytokines like IFN-γ and IL-17.
• MicroRNAs (miRNAs) regulate immune cell development, but their specific role in MAIT cell maturation is not fully understood.
• MicroRNA-155 (miR-155) is implicated in various cellular processes, yet its function in MAIT cell development requires clarification.

Purpose of the Study:

• To investigate the role of miR-155 in the development and function of MAIT cells.
• To determine if miR-155 is essential for MAIT cell maturation and subset differentiation.

Main Methods:

• Generated a CD4Cre.miR-155 knock-in mouse model for miR-155 overexpression in T cells.
• Analyzed MAIT cell populations in miR-155 overexpressing and knockout mice.
• Assessed MAIT cell maturation, subset differentiation (MAIT1, MAIT17), and cytokine production (IL-17).

Main Results:

• Overexpression of miR-155 reduced MAIT cell numbers and frequencies, impaired thymic maturation by downregulating PLZF, and skewed differentiation towards MAIT1 while inhibiting MAIT17.
• miR-155 overexpression altered MAIT cell subsets, increasing CD4-CD8+ and decreasing CD4-CD8- populations.
• Lack of miR-155 in knockout mice also promoted MAIT1 and blocked MAIT17 differentiation, but without affecting overall MAIT cell frequency, maturation, or function.
• Induced miR-155 expression inhibited peripheral MAIT cell IL-17 secretion.

Conclusions:

• Adequate miR-155 expression is essential for the normal development and function of both MAIT1 and MAIT17 cell subsets.
• miR-155 plays a critical regulatory role in MAIT cell maturation and cytokine production.
• Dysregulation of miR-155 impacts MAIT cell subset balance and effector functions.