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. Author manuscript; available in PMC: 2009 Nov 1.
Published in final edited form as: Hum Immunol. 2008 Sep 21;69(11):781–789. doi: 10.1016/j.humimm.2008.08.283

Figure 2. Possible mechanisms of suppression by CD8+ suppressor T cells (Ts).

Figure 2

Various suppression mechanisms by CD8+ Ts have been proposed so far. (a) CD8+CD28−Foxp3+ Ts upregulate inhibitory receptors, immunoglobulin-like transcript (ILT) 3 and ILT4 on antigen-presenting cells (APC), rendering APC tolerogenic. Costimulatory molecules on APC, CD80, and CD86 are also downregulated. (b) Immunosuppressive cytokines such as interleukin (IL)-10, TGFβ, IFNγ, and CCL4 are secreted by CD8+ Ts. (c) Major histocompatibility complex (MHC) class Ib molecule (Qa-1 in mice and HLA-E in humans)-restricted CD8+ Ts kill activated effector CD4+ T cells and dampen immune reactions. (d) CD8+ cytotoxic lymphocytes (CTL) work as suppressive T cells. When CTL encounter antigen-bearing APC, CTL may kill APC and attenuate immune responses.