Introduction: Although described in the 70’s, CD8⁺ regulatory T cells (Tregs) remains incompletely understood and to date, although several markers are used to define them, they remain inconsistent. The identification of good markers, as it was done for CD4⁺ Tregs; remains an urgent task and a challenge to advance our understanding.
Methods: Herein, we addressed the heterogeneity within total CD8⁺ T cells using single cell CITEseq and VDJ T cell receptor sequencing. We included markers used to previously identify Tregs, in particular CD45RC described by our team and others to divide effector (CD45RC^high) and pro-regulatory (CD45RC^low/-) CD8⁺ T cells. 7K non-stimulated CD8⁺ T lymphocytes, including CD8⁺CD45RC^low/- Tregs and CD8⁺CD45RC^high T cells of 4 healthy volunteers were analyzed.
Results: These analyses enabled the characterization of the transcriptomic heterogeneity at a single cell level from steady state total CD8⁺ T cells and allowed definition of regulatory CD8⁺CD45RC^low/- Treg subsets. Functional analysis using cell sorting and suppressive assays highlighted the suppressive potential of the CD8⁺CD45RC^low/-TNFR2⁺CD29^low Tregs subset.
Conclusion: To date, to our knowledge, this is the largest characterization study of human CD8⁺ Tregs, this huge data resource will help in the current revival of CD8⁺ Tregs in research, will improve our understanding of T cell heterogeneity and will help translate CD8⁺ Tregs to the clinic.