Cutting edge: The mouse NK cell-associated antigen recognized by DX5 moncoclonal antibody is CD49b (alpha(2) integrin, very late antigen-2)

DX5 mAb is a useful reagent because it stains NK cells from all mouse strai ns examined. We have identified the molecule recognized by DX5 mAb by using a retrovirus-mediated expression cloning system. A 5-kb cDNA encoding a pr otein that is reactive with the DX5 mAb was isolated from a NK cell cDNA li brary, and this molecule was identical with CD49b (very late Ag-2, alpha (2 ) integrin). The DX5 mAb reacted with transfectants expressing CD49b, and b inding of DX5 to the NK cells and CD49b transfectants was blocked in the pr esence of other anti-CD49b mAbs. When NK1.1(+) NK cells were cultured with IL-2, they progressively lost reactivity with DX5 mAb as a consequence of c ellular proliferation. Cytotoxicity mediated by the DX5(+) NK cells was dra matically higher as compared with DX5(-) NK cells. Therefore, DX5 mAb recog nizes CD49b and can be used to define functionally distinct subsets of NK c ells.