Intracellular tubercle bacilli-alveolar macrophage lysosomal enzymes interaction in experimental tuberculosis.

This study is an attempt to understand the mechanism of macrophage activation and its effect on the microbicidal properties of the macrophage. Alveolar macrophages (AM) from normal and BCG-vaccinated guinea pigs were harvested at intervals of 1, 7, 14, 21, and 28 days. Half of the guinea pigs from each group were challenged intratracheally with Mycobacterium tuberculosis H37Rv. In AM, the levels of three lysosomal enzymes, beta-galactosidase (beta-gal), N-acetylglucosaminidase (N-ac), and lysozyme (lyso), were measured histochemically. The percentage of AM staining positively for these enzymes and the intensity of this staining were estimated as parameters of AM activation, along with the number of intracellular bacilli in these cells. Histochemical methods are preferred to biochemical methods as only the former indicate activation in individual cells. The enzymatic responses of AM depend on the type of vaccination and infection. Thus, beta-gal activity was significantly enhanced in immune animals whereas no such enhancement of activity was observed in the case of N-ac and lyso. The N-ac content was higher in infected animals and in the immune group, whereas lyso fluctuated at different time intervals after infection.