CD244(Cluster of Differentiation 244) is a human protein encoded by the CD244 gene. It is also known as Natural Killer Cell Receptor 2B4. Tangye et al.(1999) mapped the 2B4 gene to 1q22. Suzuki et al.(2008) identified a functional single-nucleotide polymorphism(SNP) in the CD244 gene that contributes to rheumatoid arthritis susceptibility. Functional analysis by Boles et al.(1999) demonstrated that engagement of 2B4 with specific antibody activates NK cytolytic activity. Using recombinant human NK cell-activating ligand 2B4 fused to domains 3 and 4 of rodent Cd4 and flow cytometric analysis, Brown et al.(1998) demonstrated that CD48 binds to 2B4. Watzl et al.(2000) showed that antibody-mediated cross-linking of 2B4 leads to its rapid tyrosine phosphorylation, which is necessary for 2B4-mediated killer cell activity.