 Normally, the SAP protein is expressed in the cytoplasm of T- and NK-cells, where it binds to the cytoplasmic domain of the surface receptor called signaling lymphocyte activation molecule (SLAM).This binding initiates a signal transduction pathway, which results in the modulation of IFN-γ.A deletion in the SH2D1A gene leads to a non-functional SH2 domain on the SAP protein, making it unable to bind to SLAM.