2B4, also known as CD244, is a cell surface glycoprotein belonging to the CD2 subgroup of the immunoglobulin superfamily. It acts as a high-affinity receptor for CD48. It is expressed by natural killer (NK) cells and CD8+ T cell subsets. It can regulate killing by CD8+ T cells and NK cells, and IFN-gamma secretion by NK cells. It may also regulate NK cell and T cell proliferation.