Macrophage functional heterogeneity in vivo. Macrolocal and microlocal macrophage activation, identified by double-staining tissue sections of BCG granulomas for pairs of enzymes.

BCG lesions were produced in the skin of rabbits, and biopsies were performed at 7, 21, and 42 days, when they were developing, maximal in size, and almost healed, respectively. Tissue sections were prepared and stained histochemically for several enzymes. The percentage of cells stained for a given enzyme and the distribution of such cells within lesions of various ages were determined. Seven-day BCG lesions contained few esterase- and beta-galactosidase-positive macrophages, but 21-day lesions contained many, especially in the viable and nonviable tuberculous granulation tissue at the edge of the now prominent caseous necrotic center. Both 7-day and 21-day lesions contained many acid phosphatase- and cathepsin-D-positive macrophages, which were numerous in the more peripheral parts of the lesion, where little or no necrosis was present. Enzyme patterns in 42-day lesions resembled those in 21-day lesions. The role of each of these enzymes in the development and regression of the BCG lesion is unknown. Nonetheless, these studies clearly demonstrate that this macrophage population is heterogeneous and that macrophages carry out different functions in different parts of the lesion at different times. Histochemical techniques were developed to stain two enzymes in the same tissue section. The first stain usually contained a naphthol substrate and produced a red color; the second stain contained an indoxyl substrate and produced a blue color. A cell staining with both was colored purple. The peroxidase-antiperoxidase immunocytochemical technique for cathepsin D (producing a red color) was also employed. 1) Red esterase (hydrolyzing naphthol AS-D acetate) and beta-galactosidase, and 2) red esterase and blue esterase (hydrolyzing 5-bromo-4-chloro-indoxyl acetate), probably the same enzyme, were usually present in the same macrophage. In contrast, each of the following enzyme pairs was usually present in a different macrophage: 3) cathepsin D and beta-galactosidase, 4) cathepsin D and blue esterase, 5) acid phosphatase and beta-galactosidase, and 6) acid phosphatase and blue esterase. Roughly 10% of the macrophages stained for one enzyme existed side by side with macrophages stained for a different enzyme. These results suggest that local macrophage activation is under two levels of control. The first, macrolocal control, would determine the overall enzyme distribution in the lesion; whereas the second, microlocal control, would determine enzyme distribution on a cell-by-cell basis, ie, how two neighboring macrophages can each be rich in a different enzyme.