MICA/B (E9N7G) Rabbit mAb #64899

Natural killer group 2D (NKG2D) is an activating receptor expressed on NK and some T cells. It recognizes a variety of ligands that belong to the non-classical MHC class I family, including MICA, MICB, ULBP1–6 in human and Mult1, H60 (a, b, and c), and Rae-1 (α-ε) in mice. These ligand proteins are not expressed in most tissues under normal conditions, but are expressed in cells under stress, such as viral infection and malignant transformation. Engagement of NKG2D by these ligands activates cytolytic activity of NK and T cells against target cells, providing immunosurveillance. Some of these ligands are polymorphic. There are more than 100 different alleles for MICA, 40 for MICB, and around 20 for ULBPs (1-4). In addition, some of these ligands can be proteolytically cleaved from the cell surface to become soluble forms. The interaction of soluble ligands with NKG2D results in endocytosis and degradation of ligand-receptor complexes, therefore suppressing NKG2D-mediated immunosurveillance (5,6). However, recent data also demonstrated that soluble ligands can promote NK cell activation and tumor rejection (7,8).