Natural Killer Cell Activation
Innate lymphocyte killing of virus-infected and tumor cells via receptor balance.
Overview
NK cell activation is governed by the balance of activating receptors (NKG2D, NKp30, NKp46, CD16) and inhibitory receptors (KIR, NKG2A/CD94). Inhibitory receptors recognize MHC class I — its downregulation ('missing self') tips the balance toward activation. Activated NK cells release cytotoxic granules (perforin, granzymes) and produce IFN-γ and TNF-α. Antibody-dependent cellular cytotoxicity (ADCC) occurs via CD16 binding antibody-coated targets.
Cellular Location
NK cell surface → target cell
Clinical Significance
First-line defense against tumors and viruses; ADCC is the mechanism of therapeutic antibodies (rituximab, trastuzumab); NK cell therapies emerging in oncology.
Key Molecules
Key Enzymes
Related Pathways
Type I Interferon Response
Antiviral defense system activating hundreds of interferon-stimulated genes.
Intrinsic Apoptosis (Mitochondrial)
Cell death triggered by internal stress via mitochondrial cytochrome c release.
Antigen Processing & Presentation
MHC-mediated display of peptide antigens to T cells.