Stress-induced NKG2D ligand

Stress-induced NKG2D ligands are a group of cell surface proteins expressed at low levels on healthy cells but strongly upregulated in response to cellular stress such as DNA damage, viral infection, or malignant transformation. The most studied human members are the major histocompatibility complex class I polypeptide-related sequence A and B (MICA and MICB), along with the UL16-binding proteins (ULBP1–6)[3][5]. These molecules serve as "induced-self antigens," marking abnormal self-cells for recognition by innate immune effectors. Their primary function is to bind the activating receptor NKG2D found on natural killer (NK) cells and subsets of T lymphocytes. This interaction triggers cytotoxic responses against stressed, infected, or transformed target cells—most notably tumor cells—making these ligands attractive targets for immunotherapy strategies such as CAR-T therapies engineered with an NKG2D-based recognition domain[1]. However, tumors can evade this surveillance by proteolytic shedding of these ligands into soluble forms through enzymes like ADAM10/17 or matrix metalloproteinases. This reduces their surface density and impairs immune detection while also potentially causing systemic immunosuppression if soluble forms bind circulating NK/T-cell receptors[2]. Additionally, inappropriate expression in non-malignant tissues could lead to off-target effects. In summary, stress-induced NKG2D ligands represent a family rather than a single molecule; they play critical roles in anti-tumor immunity but present challenges related to specificity and potential toxicity when targeted therapeutically[3][5].

Other names

Induced-self antigenNKG2D ligandMHC class I chain-related protein A (MICA)MHC class I chain-related protein B (MICB)UL16-binding proteins (ULBP1-6)

Activation of natural killer (NK) cells and cytotoxic T lymphocytes via binding to the NKG2D receptor, leading to immune-mediated killing of stressed or transformed cells[3][5]