NKG2D and its ligands

NKG2D is an activating immunoreceptor, first recognized on NK cells but subsequently found on gamma delta T cells, CD8(+) alpha beta T cells and macrophages. In NK cells, inhibitory signals are generally dominate over activating signals. However, activating signals mediated through engagement of NKG2D by its ligands on target cells can bypass signals transmitted through inhibitory NK receptors, allowing NKG2D to function as a master-switch in determining the activation status of NK cells. NKG2D is important for T cell and NK cell-mediated immunity to viruses and tumouts, and has roles in autoimmune disease, allogeneic trans- and xenotransplantation. Depending upon the situation, development of strategies to either plantation, block or to enhance the interactions between NKG2D and its ligands may have important implications for human health and disease. (C) 2009 Elsevier Ltd. All rights reserved.