CD49f defines a subset of dysfunctional regulatory T cells circulating in the human peripheral blood

The therapeutic use of regulatory T cells (Tregs) in patients with autoimmune disorders has been hampered by the biological variability of memory Treg populations in the peripheral blood. In this study, we reveal through a combination of quantitative proteomic, multiparametric flow cytometry, RNA-seq data analysis and functional assays, that CD49f is heterogeneously expressed among human Tregs and impacts their immunomodulatory function. High expression of CD49f defines a subset of dysfunctional Tregs in the human blood characterized by a Th17-like phenotype and impaired suppressive capacity. CD49f is similarly distributed between naïve and memory Tregs and impacts the expression of CD39, CTLA-4, FoxP3 and CCR6 specifically in the memory compartment. Accumulation of CD49f high memory Tregs in the blood of ulcerative colitis patients correlates with disease severity. Our results highlight important considerations for Treg immunotherapy design in patients with inflammatory bowel disease which could possibly extend to other autoimmune disorders.