NKG2D ligand (NKG2DL)

NKG2D ligands are a diverse family of stress-inducible cell surface glycoproteins (not a single molecule) that include MICA, MICB (MHC class I chain–related proteins), and UL16-binding proteins (ULBPs, also called RAET1 proteins)[3][5][6]. They are rarely expressed on healthy cells but are upregulated on cells with cellular stress, malignancy, infection, or transformation, marking these targets for recognition by cytotoxic lymphocytes. The ligands are recognized by the activating NKG2D receptor, which is found on natural killer (NK) cells, CD8+ T cells, and cytokine-induced killer (CIK) cells. Engagement of NKG2D with its ligands triggers cytotoxicity and cytokine release, aiding immune surveillance and tumor elimination[3][4][6][2]. Tumors often evade immune surveillance by shedding these ligands as soluble molecules (sNKG2DL), impairing immune cell activation and correlating with poor prognosis[1][3][7]. While the NKG2D/NKG2DL axis is considered a promising immunotherapy target, the heterogeneity of ligands, their regulation, and ligand shedding present complexities for therapeutic intervention[1][3][5]. Note: - The query's phrasing is not ideal: "Tumor cell membrane proteins recognized by NKG2D receptor on CIK cell" describes a *class* of proteins (NKG2D ligands), not a single canonical molecule. There is no single "NKG2D ligand;" accurate mapping requires specifying whether it refers to **MICA**, **MICB**, **ULBP1–6**, or others, each of which could be a separate canonical entry. If you require structured data for each member, treat "NKG2D ligand" as a family header and create separate entries for each individual ligand. - is_incorrect: true, because this is not a specific protein name but rather a group/class of targets; needs refinement for canonical target mapping; cannot return a single, unique "official" name.

Other names

MICAMICBULBP1ULBP2ULBP3ULBP4ULBP5ULBP6RAET1Rae-1 (murine)MULT1 (murine)H60 (murine)NKG2D receptor ligand

Drugs/enhancers aim to increase ligand expression on tumors to promote immune cell targeting Blockers or antibodies can inhibit ligand shedding or neutralize soluble ligand forms to restore NKG2D-dependent immunity Chimeric antigen receptor (CAR)-based therapeutics targeting NKG2D ligands are under development[5][1].