There is a considerable body of evidence to suggest that the intercellular transfer of cell-surface proteins between immune cells as commonplace and important [Nat Rev Immunol. 2007; 7:238-43]. In particular, our laboratory has studied the exchange of proteins between NK cells and their target cells [e.g. J Exp Med. 2001; 194:1507-17, PNAS 2004; 101:16873-8]. Most recently, we have reported evidence for functional consequences of transfer of MICA from target cells to NK cells [J Immunol. 2007; 178:3418-26] and shown that the mechanism by which proteins exchange between cells involves transfer of specific membraneous structures[Traffic 2007; 8:1190-1204].