ULBP4 is a ligand of Natural killer group 2D (NKG2D), an activating receptor expressed on NK and some T cells. ULBP4 is not expressed in most tissues under normal conditions, but is expressed in cells under stress, such as viral infection and malignant transformation. Engagement of NKG2D by ULBP4 activates cytolytic activity of NK and T cells against target cells, providing immunosurveillance.
