Activation of p21ras by cytokines and chemoattractants in human eosinophils and neutrophils. In (A) eosinophils (6 × 10⁶) or (B) neutrophils (10⁷) were stimulated as indicated (IL-5, 10⁻¹⁰ mol/L; PAF, 10⁻⁶mol/L; fMLP, 10⁻⁶ mol/L; GM-CSF, 10⁻¹⁰mol/L) before lysis and incubation with GST-Raf1(RBD) to bind GTP-bound p21ras as described in Materials and Methods. Samples were analyzed by SDS-PAGE and immunoblotting with a MoAb against p21ras. The position of GTP-bound p21ras is marked by an arrowhead. This is representative of three individual experiments.