Mouse CD244, also known as 2B4, is a receptor belonging to the CD2 family of proteins involved in non- MHC-restricted cytotoxicity. It is expressed on all natural killer (NK) cells, IL-2 activated NK (LAK) cells, NKT cells, and a subset of T lymphocytes, including dendritic epidermal T cells. At least there are two isoforms of CD244.2 proteins that differ in the length of the cytoplasmic domain. The long form functions in an inhibitory manner, while the short form functions in an activating manner. The ligand of CD244 is CD48, which expressed on all hematopoietic cells. It was reported that CD244 interacts with CD48 is essential for IL-2-driven expansion and activation of murine NK cells. The 2B4 antibody reacts with CD244.2, the 2B4 allloantigen which is expressed on C57BL/6 mice, but not on Balb/c mice.