2B4 is a transmembrane receptor which is expressed primarily on natural killer cells. It plays a role in activating NK-mediated cytotoxicity through its interaction with CD48 on target cells in a subset of CD8 T cells [1]. The structure of 2B4 consists of an immunoglobulin variable domain fold and contains two beta-sheets. One of the beta-sheets, the six-stranded sheet, contains structural features that may have a role in ligand recognition and receptor function [1].

1: NMR structure of the natural killer cell receptor 2B4 (CD244): implications for ligand recognition. Ames JB, Vyas V, Lusin JD, Mariuzza R; Biochemistry. 2005;44:6416-6423. PMID:15850375