Tumor cell–Natural Killer cell immune synapse (NKIS)

The tumor cell–Natural Killer (NK) cell immune synapse is a specialized, supramolecular signaling platform formed at the contact site between an NK cell and a tumor cell. This interface is characterized by the highly organized rearrangement of membrane receptors, signaling molecules, and the actin cytoskeleton into concentric rings known as supramolecular activation clusters (SMACs) (Orange, 2008, Nature Reviews Immunology). The synapse functions as a critical checkpoint where the NK cell integrates a multitude of activating signals (e.g., from NKG2D, DNAM-1, and CD16) and inhibitory signals (e.g., from KIRs and NKG2A) to determine whether to release cytolytic granules containing perforin and granzymes (Mace et al., 2014, Molecular Immunology). In many cancers, the effectiveness of this synapse is compromised by tumor-mediated immunosuppression, such as the downregulation of activating ligands or the upregulation of HLA-E, which engages inhibitory receptors. Modern immunotherapy seeks to modulate this synapse using checkpoint inhibitors, bispecific killer cell engagers (BiKEs), and CAR-NK cells to overcome evasion mechanisms and restore potent anti-tumor responses (Long et al., 2013, Annual Review of Immunology).

Other names

Natural Killer cell immune synapseNKISCytolytic synapseNK-tumor cell interfaceNK cell immunological synapse

Therapeutic agents modulate the NK cell immune synapse by either blocking inhibitory receptor-ligand interactions (checkpoints) or by cross-linking activating receptors on NK cells with tumor-associated antigens to trigger directed exocytosis of lytic granules.