Involvement of inhibitory NKRs in the survival of a subset of memory-phenotype CD8(+) T cells

Inhibitory natural killer receptors (NKRs) such as killer cell immunoglobul in-like receptors (KIRs) in humans and Ly49 molecules in mice are expressed on NK cells and recognize multiple major histocompatibility (MHC) class I proteins. In humans and mice, a subset of CD8(+)T cells also expresses NKRs and harbors a memory phenotype. Using mice that are transgenic for KIR2DL3 and its cognate HLA-Cw3 ligand, we show that engagement of inhibitory NKRs selectively drives the in vivo accumulation of a subset of memory-phenotyp e CD8(+) T cells that express the beta chain of the interleukin 2 receptor. In vitro, recognition of MHC class I molecules by inhibitory NKRs on T cel ls down-regulated activation-induced cell death. These results unveil an MH C class I-dependent pathway that promotes the survival of a subset of memor y-phenotype CD8(+)T cells and also reveal an unexpected biological function for inhibitory NKRs on T cells.