Killer immunoglobulin-like receptors (KIRs) are polymorphic receptors for human leukocyte antigens (HLAs) that provide positive or negative signals controlling lymphocyte activation. Expression of inhibitory KIRs by CD8+T cells affects their survival and function, which is linked to improved antiviral immunity and prevention of autoimmunity. In this issue of theJCI, Zhang, Yan, and co-authors demonstrate that increased numbers of functional inhibitory KIR-HLA pairs equating to greater negative regulation promoted longer lifespans of human T cells. This effect was independent of direct signals provided to KIR-expressing T cells and was instead driven by indirect mechanisms. Since the long-term maintenance of CD8+T cells is critical for immune readiness against cancer and infection, this discovery has implications for immunotherapy and the preservation of immune function during aging.