Natural killer cell group 2 member D ligands (NKG2DL)

Natural killer (NK) cell receptor ligands, specifically the Natural killer cell group 2 member D ligands (NKG2DLs), are a group of proteins including MHC class I polypeptide-related sequence A (MICA), MICB, and the UL16-binding protein (ULBP) family. These ligands are typically absent or expressed at low levels on healthy cells but are rapidly upregulated in response to cellular stressors such as DNA damage, oxidative stress, viral infection, or malignant transformation [PMID: 21807380]. They function as critical "danger signals" recognized by the activating receptor NKG2D on NK cells and certain T cell subsets, triggering the targeted destruction of the compromised cell [PMID: 30842645]. In many cancers, tumors employ immune evasion strategies such as the proteolytic shedding of MICA and MICB from the cell surface, which reduces ligand density and creates soluble decoys that impair immune cell function [PMID: 29593067]. Therapeutic strategies targeting this axis include monoclonal antibodies designed to inhibit ligand shedding, NKG2D-Fc fusion proteins, and chimeric antigen receptor (CAR) therapies, such as CYAD-01, which utilize the NKG2D receptor to redirect immune cells against a broad spectrum of ligand-positive tumors [Celyad Oncology].

Other names

MICAMICBULBP1ULBP2ULBP3ULBP4ULBP5ULBP6Stress-induced ligandsMHC class I polypeptide-related sequence AMHC class I polypeptide-related sequence BUL16-binding proteinsNKG2D ligands

Activation of the NKG2D receptor on NK cells and T cells to induce targeted lysis of ligand-expressing cells; or prevention of ligand shedding to maintain immune visibility.