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Intracellular tubercle bacilli-alveolar macrophage lysosomal enzymes interaction in experimental tuberculosis
S Chandrasekhar1, M K Mukherjee
1Microbiology Department, Vallabhbhai Patel Chest Institute, University of Delhi, India.
Abstract:
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.
Insights
This study investigated macrophage activation and microbicidal properties using lysosomal enzyme levels in guinea pigs. BCG vaccination enhanced beta-galactosidase activity, indicating immune response impacts macrophage function.
Area of Science:
- Immunology
- Cell Biology
- Microbiology
Background:
- Macrophage activation is crucial for controlling microbial infections.
- Lysosomal enzymes are key indicators of macrophage activation status.
- Understanding these mechanisms informs strategies against tuberculosis.
Purpose of the Study:
- To elucidate the mechanism of macrophage activation.
- To assess the impact of BCG vaccination and Mycobacterium tuberculosis infection on macrophage microbicidal properties.
- To evaluate lysosomal enzyme activity as a marker for macrophage activation.
Main Methods:
- Alveolar macrophages (AM) were obtained from guinea pigs at various time points post-BCG vaccination and/or Mycobacterium tuberculosis challenge.
- Histochemical analysis was used to measure the levels and intensity of beta-galactosidase, N-acetylglucosaminidase, and lysozyme in individual AM.
- Intracellular bacilli counts were determined to assess microbicidal activity.
Main Results:
- BCG vaccination significantly enhanced beta-galactosidase activity in AM.
- N-acetylglucosaminidase levels were elevated in infected and BCG-vaccinated animals.
- Lysozyme activity showed fluctuations over time following infection, with no consistent enhancement due to vaccination.
Conclusions:
- Enzymatic responses in AM are modulated by vaccination and infection status.
- Beta-galactosidase serves as a sensitive indicator of immune activation in AM.
- Histochemical assessment of lysosomal enzymes provides valuable insights into individual cell activation and microbicidal capacity.