Tyrosine phosphorylation of WASp in XLA platelets stimulated with CRP. (A) WASp was immunoprecipitated from resting or CRP (3 μg/mL)-stimulated platelets. Proteins were resolved on 10% SDS-PAGE, transferred, and immunoblotted using the antiphosphotyrosine MoAb 4G10 (upper panel). Reprobing with the anti-WASp MoAb confirmed that a similar level of WASp was present in control and XLA platelets (bottom panel). One experiment is shown that is representative of 3. (B) WASp was immunoprecipitated from resting platelets from control (WT) and WAS patients. Proteins were resolved on 10% SDS-PAGE, transferred, and immunoblotted using the WASp MoAb.