Figure 1

CD8⁺ regulatory T cell (Treg) phenotypes. Natural CD8⁺CD122⁺ Tregs are CD44^highCD62L⁺CD127⁺ and partially PD-1-positive (PD-1^+/−) but are FoxP3-negative. Natural CD8⁺CD28⁻ Tregs (nTreg) are CD44^lowCD62L⁺ but GITR-CTLA4-FoxP3⁻; whereas, induced CD8⁺CD28⁻ Tregs (iTreg) are CD44^highCD62L⁺, but GITR⁺CTLA4⁺FoxP3⁺. CD8⁺CD103⁺ Tregs are CD44^lowCD62L^highFoxP3⁺. GITR = Glucocorticoid-induced tumor necrosis factor receptor-related protein, CTLA4 = cytotoxic T-cell antigen 4.