On the one hand, there are reports suggesting that 2B4 phosphorylation takes place independently from SAP: pervanadate treatment of NK cells from XLP patients leads to 2B4 phosphorylation (Parolini et al., 2000), and antibody mediated cross-linking of 2B4 has recently been reported to induce receptor phosphorylation in NK cells from SAP−/− mice, as well as from mice lacking all SAP-family adaptors (Dong et al., 2012). Here, CD244 is linked to X-linked lymphoproliferative disease.