NCR2 (natural cytotoxicity triggering receptor 2), also known as NKp44, is an activating immunoreceptor expressed on natural killer (NK) cells and innate lymphoid cells that mediates cytotoxic and immunoregulatory functions 1. Primary function: NCR2 serves as a cytotoxicity-activating receptor that enhances NK cell-mediated tumor cell lysis 2. Mechanism: NCR2 recognizes diverse ligands including platelet-derived growth factor (PDGF)-DD on tumor cells and HLA-DP on activated CD8+ T cells 23. Upon ligand engagement, NCR2 triggers NK cell secretion of interferon-gamma and tumor necrosis factor-alpha, inducing tumor cell growth arrest 2. NCR2 also participates in immune regulation by mediating HLA-DP-dependent editing of CD8+ effector T cell populations, preventing hyper-expanded T cell clones 3. Disease relevance: Higher NCR2 expression correlates with improved survival in glioblastoma, and NCR2+ NK cells more effectively control dissemination of PDGF-DD-expressing tumors 2. Additionally, NCR2+ innate lymphoid cells in the female genital tract display rapid antiviral responses to HIV stimulation 4. Clinical significance: NCR2 expression represents a potential biomarker for tumor prognosis and immunotherapy response, with therapeutic potential for enhancing NK cell-mediated tumor surveillance 1.