Pre-existing chromatin accessibility and gene expression differences among naive CD4⁺ T cells influence effector...

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• CD4+ T-cells exhibit plasticity, differentiating into various effector types upon activation.
• The heterogeneity within naive CD4+ T-cell populations prior to antigen encounter is not fully understood.
• Investigating pre-existing differences may reveal mechanisms governing T-cell differentiation.

Purpose of the Study:

• To determine if naive CD4+ T-cells possess inherent transcriptional and chromatin differences.
• To assess whether these pre-existing differences modulate the potential for effector lineage differentiation.
• To explore the role of T-cell receptor (TCR) signaling in establishing these naive cell states.

Main Methods:

• Single-cell RNA sequencing to analyze gene expression variability in naive CD4+ T-cells.
• Utilizing CD5 expression as a marker for tonic TCR interactions and self-reactivity.
• Sorting naive CD4+ T-cells based on CD5 expression levels to isolate distinct populations.
• Analyzing chromatin landscapes in relation to TCR signaling history.

Main Results:

• Genes involved in T-cell receptor (TCR) signaling are major sources of variability among naive CD4+ T-cells.
• Pre-existing transcriptional differences correlate with the choice between follicular helper T (Tfh) and non-Tfh effector lineages.
• TCR signal strength during thymic development influences the chromatin landscape of naive CD4+ T-cells.
• These developmental differences in chromatin structure impact subsequent effector potential.

Conclusions:

• Naive CD4+ T-cells are not a uniform population and exhibit heterogeneity before antigen exposure.
• Tonic TCR signaling and its strength during thymic development play a critical role in shaping naive T-cell states.
• These pre-existing differences, established during development, pre-determine aspects of CD4+ T-cell effector lineage commitment.