Apoptosis of eosinophils in asthma.

Eosinophils play a major role in the onset and maintenance of bronchial inf lammation and tissue injury in asthma. Like other leukocytes, eosinophils p resent in excessive numbers in inflamed tissues are removed by apoptosis. T his phenomenon, also called 'programmed cell death', allows elimination of dangerous or redundant cells, thereby ensuring maintenance of tissue homeos tasis. It has been suggested that a defect in eosinophil apoptosis would pa rticipate in the development and persistence of allergic airways inflammati on in asthma. Eosinophil apoptosis, as well as the expression and function of various molecules determining this process, are closely regulated by var ious stimuli, including cytokines, lipid mediators and growth factors relea sed by various cell types and by the eosinophil itself, as well as exogenou s molecules, such as glucocorticoids. These stimuli have been shown to alte r the expression and function of different molecules involved in the cascad e of events characterising the apoptotic process, particularly Bcl-2 family proteins and the pro-apoptotic membrane glycoprotein, Fas. These observati ons, together with a better understanding of the mechanisms underlying eosi nophil apoptosis, will help to more clearly define the molecular events inv olved in accumulation of these cells in blood and tissues and to identify p otential new targets for the treatment of allergic diseases. (C) 2000 Editi ons scientifiques et medicales Elsevier SAS.