[Kinetics of pulmonary defense in deep lung (author's transl)]

The association of different experimental methods using radioactive particulate aerosols with bronchial washing and morphometric techniques reveals the importance of alveolar macrophages in antibacterial defense and the interest of their quantitative evaluation. The study of the kinetics of pulmonary phagocytic systems has shown a "capillary compartment", which consists of a reserve of monocytes which are temporarily present in the lung and in transit through it. This reserve represents 4.6% (sigma=1.4) of the cells from deep in the lung and is much larger than the systemic monocytic pool. 0.5% of these monocytes are in a phase of DNA synthesis. This capillary compartment must be clearly separated from interstitial phagocytes, the number of which is insignificant under physiological conditions. The phagocytic relay by polynuclear elements appears during bacterial aggression and is interdependent with macrophagic population. The particularities of the immune defenses of the distal parts of the lung are stressed especially in comparison with systemic defenses.