The 1D11 monoclonal antibody specifically binds to NKG2D, a 42 kDa type II transmembrane glycoprotein that is also known as CD314 and KLRK1. NKG2D is a member of the C-type lectin family and is expressed on human NK cells. This activating receptor binds strongly to several ligands including MICA and MICB and ULBP-1, -2, and -3 proteins that are expressed by different target cell types. Different from natural cytotoxicity receptor (NCR), NKG2D expression is not confined to NK cells. It is also expressed on virtually all TCR γ/δ+ and CD8+TCR α/β+ T cells. NKG2D functions as a triggering receptor involved in natural cytotoxicity mediated by normal NK cells against a variety of tumors or normal target cells. Importantly, NKG2D can complement the role of NCR in tumor cell lysis. Remarkably, the combined maskings of NCR and NKG2D can reportedly lead to a complete inhibition of NK-mediated lysis of all tumor or normal cells. The 1D11 antibody can reportedly block or stimulate the function of NKG2D-positive cells.