Intracellular adapter molecules

Lymphocyte antigen receptor engagement leads to the initiation of numerous signal transduction pathways that direct ultimate cellular responses.' In r ecent years, it has become apparent that adapter molecules regulate the cou pling of receptor-proximal events, such us protein tyrosine kinase activati on, with end results such as inducible gene expression and cytoskeletal rea rrangements. While adapter molecules possess no intrinsic enzymatic activit y, their ability to mediate protein-protein interactions is vital for the i ntegration and propagation of signal transduction cascades in lymphocytes. Recent studies demonstrate that intracellular adapter molecules function as both positive and negative regulators of lymphocyte activation.