Anergic Th1 cells express altered levels of the protein tyrosine kinases p56lck and p59fyn

Tolerance in T lymphocytes can result from clonal anergy, or paralysis, of Ag-specific T cells. To investigate the molecular mechanisms responsible for anergy, a system in which tolerance can be induced in vitro was employed. Anergy, as defined by long-lived nonresponsiveness to normal antigenic stimulation for IL-2 production, was produced in cloned murine CD4+ Th1 cells. Here we report that such anergic Th1 cells express constitutively reduced amounts of the protein tyrosine kinase p56lck and constitutively elevated levels of the protein tyrosine kinase p59fyn. Because protein tyrosine phosphorylation is known to be important for the normal induction of IL-2 synthesis, these results suggest that T cell anergy may be maintained, at least in part, by alterations in tyrosine phosphorylation signaling events.