CD244 is expressed on all human NK cells, a subpopulation of T cells, basophils and monocytes. CD244 activates NK cell mediated cytotoxicity, induces secretion of IFN-gamma and matrix metalloproteinases, and NK cell invasiveness. Although there have been several molecules shown to interact with CD244, the signaling mechanism ofCD244-mediated activation of NK cells is still unknown. It is a high affinity receptor for CD48.