Typical traces showing the effect of PTX on intracellular Ca²⁺ transients induced by maximally effective concentrations of C5a, LTB₄ , or PAF. Eosinophils were pretreated for 2.5 hours with vehicle (CN) or PTX (1 μg/mL, see the Materials and Methods). The cells were then labeled with fura-2-acetoxymethyl ester and washed and changes in fluorescence were monitored after activation with LTB₄ (10⁻⁸ mol/L), C5a (10⁻⁷ mol/L), or PAF (10⁻⁸ mol/L). The time of the addition of the agonists is shown by the arrows. Results are expressed as the increase in the concentration of intracellular calcium (in nanomoles per liter) as a function of time (in seconds).