Interferon regulatory factor 4 sustains CD8(+) T cell expansion and effector differentiation

Area of Science:

• Immunology
• Molecular Biology
• Cellular Biology

Background:

• CD8(+) T cells are critical for adaptive immunity, undergoing activation, expansion, and differentiation upon infection.
• The precise transcriptional regulation governing these CD8(+) T cell phases remains incompletely understood.

Purpose of the Study:

• To investigate the role of interferon regulatory factor 4 (IRF4) in CD8(+) T cell responses during infection.
• To elucidate the molecular mechanisms by which IRF4 influences T cell differentiation and function.

Main Methods:

• Utilized conditional knockout mouse models to selectively ablate Irf4 in peripheral CD8(+) T cells.
• Employed transcriptional profiling and functional assays to assess T cell responses.
• Investigated the signaling pathways regulating IRF4 expression, including T cell receptor (TCR) signaling and mammalian target of rapamycin (mTOR).

Main Results:

• IRF4 is dispensable for initial CD8(+) T cell activation but vital for sustained expansion and effector differentiation.
• IRF4 promotes Blimp1 and T-bet expression while repressing cell cycle arrest and apoptosis genes.
• Selective ablation of Irf4 impaired antiviral responses, viral clearance, and host recovery from influenza infection.
• IRF4 expression is modulated by TCR signaling strength via mTOR.

Conclusions:

• IRF4 acts as a critical mediator translating TCR signaling strength into quantitative and qualitative CD8(+) T cell responses.
• IRF4 is essential for effective antiviral immunity mediated by CD8(+) T cells.
• Targeting IRF4 could be a strategy to modulate CD8(+) T cell-mediated immunity.