Costimulation through TLR2 Drives Polyfunctional CD8⁺ T Cell Responses

Area of Science:

• Immunology
• Cellular Biology
• Molecular Biology

Background:

• Optimal T cell activation depends on T cell receptor (TCR) recognition, costimulatory signals, and cytokines.
• T cells express Toll-like receptors (TLRs) that recognize danger signals, but their role in costimulation is unclear.

Purpose of the Study:

• To investigate if TLR ligands can provide costimulatory signals and enhance antigen-driven T cell activation.
• To determine the mechanisms by which TLR triggering supports T cell cytokine production.

Main Methods:

• Adaptation of flow cytometry-based fluorescence in situ hybridization for mouse T cells.
• Simultaneous detection of cytokine mRNA and protein at the single-cell level.

Main Results:

• TLR2 and TLR7 ligands significantly lower the antigen threshold required for T cell cytokine production.
• TLR triggering primarily enhances de novo mRNA transcription; mRNA stabilization requires TCR engagement.
• TLR2 costimulation, unlike TLR7, enhances mRNA stability at low antigen levels and increases polyfunctional T cells.

Conclusions:

• TLR-mediated costimulation potentiates T cell effector functions, even with suboptimal antigen levels.
• TLR2 costimulation is particularly effective in enhancing T cell responses and promoting polyfunctional T cells.