Figure 1.

(A) CD8⁺ Tregs secret various inhibitory cytokines and chemokines, including IL-10, TGF-β, IL-16, IFN-γ and CCL4. (B) CD8⁺ Tregs render the antigen-presenting cells tolerogenic and anti-inflammatory by the induction ILT3 and ILT4, or through the downregulation of CD80 and CD86 on APCs. (C) CD8⁺ Tregs serve an inhibitory function, in which TGF-β and CTLA-4 expressed on the cell surface are the key factors. (D) The cytotoxicity of CD8⁺ Tregs depends on the expression of the major histocompatibility complex class Ib molecule Qa-1 in mice and HLA-E in humans. (E) Recent advances in CD8⁺ Treg research. Treg, T regulatory cell; IL, interleukin, TGF, transforming growth factor; IFN, interferon; CCL4, chemokine (C-C motif) ligand 4; ILT, immunoglobulin-like transcript; APC, antigen-presenting cell; CTLA-4, cytotoxic T-lymphocyte associated protein 4; TCR, T cell receptor.