[Quantitative evaluation and homeostasis of alveolar macrophage populations]

The rat's alveolar macrophage population is a biological constant which significantly varies according to the season, the strain and the bacteriological state,in healthy animals. The percent rate of excreted macrophages remains constant in spite of the physiological changes of the total population variation. This rate is close to 3,5 %. So, the variations of the population are due to the changes in cell arrival. The possible different sources of alveolar macrophages are analysed and evaluated. The direct monocyte source is not sufficient to insure the stability of this population. Division of intra alveolar macrophage enables homeostasis. In pathological conditions, variations of cell populations result from two effects : reduction of excretion, positive or negative changes in cellular influx.