Comparison of platelet-activating factor-induced chemotaxis of normodense and hypodense eosinophils.

Platelet-activating factor (PAF)-induced eosinophil (EOS) migration is an important event in the development of tissue eosinophilia and allergic inflammation. EOSs are heterogeneous cells in that different states of activation have been ascribed to EOSs of varying densities. We therefore studied the ability of PAF to induce hypodense and normodense EOS chemotaxis. Both hypodense and normodense EOSs were isolated in pure form from seven subjects and studied concurrently. Dose-response and time-course experiments indicated no significant differences in PAF-induced hypodense versus normodense EOS chemotactic responses. Hypodense and normodense cells achieved maximal chemotaxis in response to 1 mumol/L of PAF, and maximal chemotaxis was achieved at 2 hours. However, marked differences in PAF-induced EOS chemotactic responses existed between patients. We conclude that PAF is a potent EOS chemoattractant, and despite reported differences in metabolic activity, normodense and hypodense EOSs exhibit similar chemotactic responsiveness to PAF.