Aggregation and Syk activation in wild type (+/+) and c-Cbl knock-out (-/-) murine platelets. Washed murine platelets were activated for indicated times with 100 ng/mL convulxin (Cvx). (A) Aggregation tracings are shown (the arrow indicates addition of Cvx). (B) Syk was immunoprecipitated as described and immunoblots were probed for phosphotyrosine. This antibody was stripped from the blot and reprobed for Syk (not shown). IP indicates immunoprecipitation.