Protein tyrosine kinase p59 super(fyn) is associated with the T cell receptor-CD3 complex in functional human lymphocytes

The binding of antigen to the multicomponent T cell antigen receptor (TcR)-CD3 complex leads to the activation of several signal transduction pathways which results in T lymphocyte proliferation and lymphokine secretion by molecular mechanisms and catalytic molecules as yet poorly defined. One of the earliest events that follows the triggering of the antigen-specific TcR-CD3 complex is a rapid tyrosine phosphorylation of several intracellular substrates suggesting stimulation of at least one protein tyrosine kinase (PTK). The findings provide direct evidence for a significant association of p59 super(fyn) with the TcR-CD3 complex under physiologically relevant conditions in functional T lymphocytes. They suggest that p59 super(fyn) is a crucial component of the TcR signal transduction machinery and that one of the earliest consequences of antigen recombination by the TcR is p59 super(fyn)-mediated phosphorylation of intracellular substrates on tyrosine residues.