Killer cell lectin-like receptor subfamily K member 1 and ligands (NKG2D-NKG2DL axis)

The NKG2D receptor (encoded by KLRK1) and its diverse array of ligands, including MICA, MICB, and the ULBP/RAET1 family, constitute a critical immune surveillance axis (UniProt P26718). NKG2D is a potent activating receptor expressed on natural killer (NK) cells, CD8+ T cells, and certain gamma-delta T cells. Its ligands are typically absent from healthy tissues but are rapidly upregulated in response to cellular stress, such as viral infection, DNA damage, or malignant transformation (PubMed: 11526521). Upon binding, NKG2D signals through the adapter protein DAP10 to trigger the release of cytotoxic granules and pro-inflammatory cytokines, leading to the destruction of the ligand-bearing cell (PubMed: 31160319). In oncology, therapeutic strategies aim to enhance this interaction through CAR-T cells or bispecific antibodies to eliminate tumors (PubMed: 29590617). Conversely, in autoimmune diseases like Crohn's or rheumatoid arthritis, the goal is often to block the receptor to prevent excessive, pathological tissue damage. A significant challenge in targeting this axis is the proteolytic shedding of ligands from tumor surfaces, which can act as decoys and downregulate receptor expression, facilitating immune escape.

Other names

NKG2DCD314KLRK1MHC class I polypeptide-related sequence A (MICA)MHC class I polypeptide-related sequence B (MICB)UL16-binding protein (ULBP)Retinoic acid early transcript 1 (RAET1)NKG2-D type II integral membrane protein

Activation of cytotoxic immune cells (NK and T cells) through NKG2D receptor binding to stress-induced ligands on target cells for oncology, or therapeutic blockade of the NKG2D receptor to inhibit pathological immune-mediated tissue damage in autoimmune conditions.