Adapters can be defined as proteins that mediate intermolecular interaction
s within a signal transduction pathway and that lack both intrinsic enzymat
ic and transcriptional activity. Their essential role in lymphocyte signali
ng was revealed by recent analyses of mice and cell lines deficient in LAT,
SLP-76 and BLNK. These and other adapters nucleate signaling complexes and
facilitate coupling of antigen receptor triggering to functional responses
in lymphocytes.