Platelet-derived growth factor can activate purified primate, phorbol myristate acetate-primed eosinophils

We are interested in the physiologic mechanisms of eosinophil activation because of the presumed participation of activated eosinophils in the inflammatory sequelae of asthma. Suspecting that other formed elements of the blood may contribute to such an activation, we examined the capacity of platelet-derived growth factor (PDGF), a product of activated platelets, to activate eosinophils. We found that highly purified monkey and human eosinophils, but not guinea pig eosinophils, were activated by PDGF (superoxide anion production) in a dose-dependent fashion. Moreover, this activation was further dependent on a prior 'priming' of the cells by a brief exposure to subthreshold concentrations of phorbol ester. The response was specific for the BB homodimer of PDGF suggesting it is receptor-dependent.