[Methods and criteria for studying polynuclear eosinophil activation].

The deleterious effects of eosinophilis in many disease associated with hypereosinophilia are due mainly to the ability of eosinophils to degranulate and release inflammatory substances into host tissues (e.g. proteins, lipid mediators, cytokines). Prior to degranulation, which may occur either after stimulation or for unexplained reasons, eosinophils undergo an activation process. This process comprises functional, metabolic, and structural changes that potentiate the stimulatory and/or regulatory activities of eosinophils. The present article describes methods that can be used for in vitro or ex vivo evaluation of polynuclear eosinophil activation. In vivo and ex vivo assessment of the activation status of eosinophils is a crucial step to a better understanding of the role played by these cells in various diseases. Up to now, the most widespread technique for evaluation of eosinophil activation consisted of studying cell density by centrifugation through discontinuous gradients. This method is both complex and time-consuming. Recently discovered surface molecules associated with eosinophil activation and technological advances allowing rapid and accurate sample analysis (whole blood flow cytometry) have opened the way to new methods for the study of eosinophils. A combination of ex vivo (flow cytometry, in situ hybridization) and in vivo (cell density analysis, titration) techniques will provide new insights into the physiology and heterogeneity of eosinophil function.