Late eosinophil mobilization induced by PAF-acether in the pleural cavity of rats.

In view of the rapid degradation of PAF in biological fluids, this study was designed to determine if late eosinophil infiltration induced in rats by PAF was derived from its direct chemotactic action. A significant and selective 5-fold increase in the pleural eosinophil counts was detected 24 h after intrapleural PAF injection. The transfer of 6-h PAF washings to the pleural cavity of recipient rats also induced a 3-fold selective accumulation of eosinophils. The protein synthesis inhibitor cycloheximide abolished the pleural eosinophil migration and the generation of transferable chemotactic activity when administered to donor but not to recipient rats. These findings suggest that a secondary protein mediator accounts for the late eosinophil mobilization induced by PAF.