Preferential human eosinophil chemotactic activity of the platelet-activating factor (PAF)...

The chemotactic responses of human blood neutrophils and of eosinophils of two different densities, which were resolved by centrifugation on gradients of polyvinylpyrrolidone-coated silica gel (Percoll), were quantified in modified Boyden micropore filter chambers using highly purified synthetic 1-0-hexadecyl-2-acetyl-sn-glyceryl-3-phosphocholine (AGEPC or PAFacether) and leukotriene B4 (LTB4) as stimuli. Maximal chemotactic responses of the densest eosinophils, less dense eosinophils, and neutrophils were evoked by 1 nM, 100 nM, and 1 microM PAFacether, respectively, and by 30-100, 30-100, and 10 nM LTB4. The magnitude of the maximal chemotactic response to PAFacether of the densest eosinophils was significantly greater than that of neutrophils. The eosinophil responses to PAFacether were chemotactic, as distinguished from chemokinetic, and were not influenced by the percentage of contaminating neutrophils. PAFacether is a more potent chemotactic factor for eosinophils than neutrophils and selectively attracts the densest population of human blood eosinophils.