Following recognition of foreign antigens, the T cell antigen receptor (TCR) transduces signals leading to clonal expansion and differentiation into effector cells. Engagement of the TCR results first in the activation of cytosolic protein tyrosine kinases, followed by initiation of multiple signaling cascades. Recently, it has been shown that regulation and integration of these signaling pathways requires formation of multimolecular complexes and the recruitment of these complexes to specific regions within the cell. This review focuses on the events leading to T cell activation including the signaling cascades and the role of adapter molecules in coordination of these pathways. In addition, the mechanism by which TCR ligation can lead to T cell removal following elimination of an antigenic challenge is discussed.
