KLRK1, also known as NKG2D ligand 4 isoform 1, is a type ll transmembrane glycoprotein having an extracellular lectin-like domain. This domain lacks the recognizable calcium-binding sites found in true C-type lectins and binds protein rather than carbohydrate ligands. It can send co-stimulatory signals to activate CD8 T cells. Also, it plays an important role in viral control. Cellular stress can induce ligands for KLRK1 which results in the cell susceptible to NK cell-mediated lysis.