Effect of the PKC inhibitor, Ro 31-8220, on eosinophil aggregation induced by (A) PAF, (B) C5a, or (C) LTB₄. Eosinophils were pretreated for 3 minutes with Ro 31-8220 (3 × 10⁻⁵ mol/L, open symbols) or vehicle (solid symbols) before the addition of PAF (10⁻¹⁰ mol/L to 10⁻⁷ mol/L), C5a (10⁻⁸ mol/L or 10⁻⁷ mol/L), or LTB₄ (10⁻¹⁰ mol/L to 10⁻⁷ mol/L). Results are expressed as the percentage of maximal aggregation induced by PMA (10⁻⁷ mol/L) and each point is the mean ± SEM for three to five experiments. **P < .01 when compared with control values.