SAP discovery : The sword edges — Beneficial and harmful

We cloned the SLAM associated protein (SAP) gene in 1995. In 1998, it was discovered that the SAP gene was defective in patients with X-linked lymphoproliferative disease. Subsequently, details on the key role of life-long immune memory (vaccination) and of life-long autoantibody production in patients suffering from autoimmune disease have been revealed. In this paper, we discuss the dual nature of SAP in humans: its beneficial effect on life-long immune memory (vaccination) and its harmful effect on life-long autoantibody production.