Hypomethylation-induced regulatory programs in T cells unveiled by transcriptomic analyses.

Area of Science:

• Immunology
• Cell Biology
• Epigenetics

Background:

• Regulatory T cells (Tregs) are crucial for immune tolerance and preventing autoimmune diseases.
• Naturally occurring Tregs (nTregs) rely on epigenetic regulation, but induced Tregs (iTregs) lack defined identity and mechanisms.
• Hypomethylation agents (HAs) can convert T cells into iTregs (HA-iTregs) with suppressive properties.

Purpose of the Study:

• To elucidate the molecular identity and mechanisms of HA-induced iTregs (HA-iTregs).
• To identify specific markers for isolating potent suppressive HA-iTreg populations.
• To compare the transcriptomic profiles of suppressive (G+) and non-suppressive (G-) HA-iTregs.

Main Methods:

• Ex vivo T cell conversion using hypomethylation agents (HAs).
• Isolation of HLA-G positive (G+) and HLA-G negative (G-) cell populations.
• High-throughput RNA-sequencing (RNA-seq) and single-cell RNA-seq analysis.
• Cytokine profiling and gene expression analysis (IDO-1, CCL17/22).

Main Results:

• HA-iTregs exhibit a distinct suppressive subset (G+ cells) marked by de novo HLA-G expression.
• G+ cells show upregulated immune-response pathways and molecular features resembling nTregs.
• FOXP3 and T-helper signatures play a minor role in G+ cell suppressive function.
• Ectopic expression of myeloid suppressor genes (IDO-1, CCL17/22) observed in G+ cells.

Conclusions:

• This study defines the molecular identity of a potent HA-iTreg population (G+ cells).
• HLA-G serves as a reliable marker for isolating suppressive HA-iTregs.
• HA-iTreg function may involve novel, ectopic myeloid-specific suppressive mechanisms.