FcγR-induced Rac activation is enhanced in SHIP-deficient macrophages. (A) SHIP^+/+ and SHIP^–/– macrophages were activated by clustering Fcγ receptors for the indicated time points. GTP-bound Rac was captured with PAK-1 PBD beads as bait from protein-matched cell lysates and visualized by Western blotting with anti-Rac antibody. Unhydrolizable GTP and GDP analogs (obtained from Chemicon International) were used as positive and negative controls, respectively. (B) Fold induction of GTP Rac in the activated samples over resting (R). The graph represents mean and SEM of 3 independent experiments. Data were analyzed by Student t test (*P ≤ .05).