The gene defective in X-linked lymphoproliferative disease controls T cell dependent immune surveillance against Epstein-Barr virus.

Our understanding of the X-linked lymphoproliferative syndrome (XLP) has advanced significantly in the past two years. The gene that is aberrant in the condition - SH2D1A/SAP, which encodes SAP (signaling lymphocytic activation molecule [SLAM]-associated protein) - was cloned, the crystal structure of its product was solved and insights into the signaling mechanisms of this small SH2-domain-containing protein via the cell surface receptors SLAM and 2B4 have been provided. SAP mutation, and not Epstein-Barr virus infection per se, may be critical for XLP.