Separation of bronchoalveolar cells from the guinea pig on continuous gradients of Percoll: functional properties of fractionated lung macrophages.

Lung macrophages from normal guinea pig lungs were separated from bronchoalveolar cells into three fractions according to buoyant density by centrifugation on continuous iso-osmotic gradients of Percoll [3]. A reproducible pattern of functional activity distinguished these three macrophage fractions. With increasing density and decreasing cell size, the respective fractions exhibited increased stimulated migration, superoxide anion release and pinocytosis, and increased protein concentration of the cells. These differences, coupled with previous observations that these fractions also exhibited morphological and cytochemical differences [3], support the notion that these fractions of macrophages may represent different stages of maturation (or differentiation) of alveolar macrophages in the lungs of normal guinea pigs.