Notch modulates human NK cell differentiation through regulation of inhibitory killer immunoglobulin-like receptor (KIR) expression and acquisition of effector function (TUM2P.890)

Abstract

Abstract The Notch signaling pathway plays a substantial role on human NK cell development, however the role of Notch on KIR upregulation and acquisition of effector function has not been explored. To evaluate how Notch influences terminal differentiation, cord blood derived NK cells or sorted KIR- peripheral blood NK cells were cultured with IL-15 for 7 days in the presence or absence of gamma-secretase inhibitor, known to inhibit Notch signaling. Inhibition of Notch signaling significantly decreased KIR expression. Conversely, co-culturing the same cells with OP9 cells bearing Notch ligands enhanced KIR expression. Overexpression of the active portion of Notch on cord blood derived NK cells after 28 days of culture resulted in a 2-fold increase in KIR expression indicating that Notch signaling plays a direct, cell intrinsic, role in KIR regulation. By knocking down delta-like 1 (DLL1) on NK cells and co-culturing them with OP9 cells expressing Notch ligands we show that DLL1 mediated cis-inhibition controls KIR expression. Notch signaling also enhances CD16 upregulation that precedes KIR expression. More important than receptor expression is function. We found that Notch signaling induces increased cytolytic effector capacity and cytokine secretion, even on post-transplant samples where NK cell function is inherently defective. Given these attributes of Notch signaling, we propose Notch agonists can enhance NK cell maturation and tumor killing in a post-transplant setting.