Status of Syk in FL cells. (A) Syk expression was visualized by Western blotting in FL cell lines and compared to B cells isolated from B-CLL patients (B-CLL) and healthy donors (BL). Actin was used as control of protein expression. Results are representative of 3 independent experiments. (B) Syk activity was evaluated by P-Tyr immunoprecipitation followed by Western blotting using an anti-Syk antibody, in FL cells and B cells isolated from healthy donors (BL) and from B-CLL patients (B-CLL). Results are representative of 3 independent experiments. (C) Effect of piceatannol on Syk activity was evaluated in Karpas-422 cells by Western blotting using an antiphospho-Syk antibody specific to tyrosine 525/526 residue. Results are representative of 3 independent experiments. (D) Effect of piceatannol on Syk activity was evaluated in RL cells by immunokinase assay as described in “Materials and methods.” Results are representative of 3 independent experiments.