This gene encodes a protein that plays a major role in the
bidirectional stimulation of T and B cells. This protein contains
an SH2 domain and a short tail. It associates with the signaling
lymphocyte-activation molecule, thereby acting as an inhibitor of
this transmembrane protein by blocking the recruitment of the
SH2-domain-containing signal-transduction molecule SHP-2 to its
docking site. This protein can also bind to other related surface
molecules that are expressed on activated T, B and NK cells,
thereby modifying signal transduction pathways in these cells.
Mutations in this gene cause lymphoproliferative syndrome X-linked
type 1 or Duncan disease, a rare immunodeficiency characterized by
extreme susceptibility to infection with Epstein-Barr virus, with
symptoms including severe mononucleosis and malignant lymphoma.
Multiple transcript variants encoding different isoforms have been
found for this gene.
