The Src kinases inhibitor PP1 reduced CD2-mediated tyrosine phosphorylation of LAT.

Wild-type Jurkat cells (10⁷ cells/test) were either left untreated or preincubated with the specific Src kinases inhibitor PP1 (20 μmol/L) at 37°C for 30 minutes and then either left unstimulated or stimulated with either OKT3 or T11₂ plus T11₃ for the indicated periods of time. Cells were then lysed in 1% Brij97 lysis buffer, and clarified PNLs were subjected to LAT immunoprecipitation as described in “Materials and methods.” Tyrosine phosphorylation of LAT is shown (upper panel). The same membrane was stripped and reblotted with anti-LAT–specific antibody (lower panel).