Rôle des polynucléaires neutrophiles et lésions du poumon profond.

The polymorphonuclear neutrophil (PMN) is virtually absent in the alveoli in the healthy subject. On the other hand, in certain infectious and fibrotic pathological states the PMN can invade, sometimes massively, the alveolar and interstitial pulmonary structures. The mechanism of recruitment of the PMN involves both exogenous and endogenous factors including secretory products of the macrophages. PMN is a defensive phagocyte which is often necessary to clear bacteria from the lung. However, through the release of toxic derivatives of oxygen and of proteolytic enzymes the PMN are capable of producing lesions within the pulmonary parenchyma. This double role of defense and aggression makes the PMN an effector cell, which is certainly important but whose activity is not isolated because its function depends mostly on interaction with other cells and mediators.