The DX27 monoclonal antibody reacts with a common epitope of KIR2DL2 (CD158b1, p58.2), KIR2DL3 (CD158b2, p58.3), and KIR2DS2 (CD158j, p50.2). It is expressed on natural killer cells and a subset of T cells. KIR-NKAT2 is a member of the immunoglobulin superfamily containing two immunoglobulin C2-type domains. Both variants and alternative isoforms of KIR-NKAT2 have been reported. The interaction of KIR-NKAT2 with specific HLA-C antigens on a target cell (HLA-Cw1, HLA-Cw3, HLA-Cw7 alleles, for example) inhibits cytotoxicity and prevents target cell lysis and death. The interactions between KIR and MHC class I are thought to be important in NK cell and T cell regulation following antigen stimulation. The absence of ligands for KIRs may lower the threshold for activation through activating receptors and increase inflammation and susceptibility to autoimmune disease.