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Intracellular acid phosphatase content and ability of different macrophage populations to kill Nocardia asteroides
Abstract:
It has been reported that the activity of lysosomal acid phosphatase decreases inversely with numbers of ingested virulent Nocardia spp. in normal murine peritoneal and alveolar macrophages. These studies suggested that this relationship correlated with the effectiveness of these macrophage populations in killing Nocardia asteroides. Experiments were designed to determine if acid phosphatase activity is affected by infection with N. asteroides in four different macrophage populations isolated from normal and nocardia-immunized mice. Macrophages were also tested simultaneously for their ability to kill N. asteroides. Peritoneal, alveolar, and splenic macrophages and Kupffer cells were infected in vitro with strains of N. asteroides of differing virulence. Uptake and killing assays were performed. Acid phosphatase levels and numbers of intracellular nocardiae were quantitated in the same macrophages, using a computer-assisted cytophotometry system. Acid phosphatase activity decreased inversely with numbers of intracellular nocardiae in macrophages that could not kill or inhibit this pathogen. Acid phosphatase activity was not significantly changed in macrophages that inhibited growth of, but did not kill, N. asteroides, whereas activity was increased or enhanced in macrophages that killed most of the ingested nocardiae. The order of nocardicidal effectiveness (and resistance to enzyme activity reduction with infection) for normal macrophages was splenic greater than peritoneal greater than alveolar greater than Kupffer. In contrast, the order of these two parameters for macrophages isolated from immunized mice was Kupffer greater than peritoneal greater than alveolar greater than splenic. These results demonstrate that lysosomal acid phosphatase activity is an effective marker of the ability of macrophages to inhibit growth of and kill N. asteroides and that macrophages isolated from different anatomical sites differ functionally from each other with respect to nocardicidal and acid phosphatase activities.
Insights
Lysosomal acid phosphatase activity in macrophages indicates their ability to fight Nocardia asteroides. Enzyme activity decreases when macrophages cannot kill the bacteria, but increases when they are effective.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Lysosomal acid phosphatase activity in macrophages has been inversely correlated with ingested Nocardia spp.
- This relationship was previously suggested to indicate macrophage effectiveness in killing Nocardia asteroides.
Purpose of the Study:
- To investigate the effect of Nocardia asteroides infection on acid phosphatase activity in four distinct murine macrophage populations.
- To assess the simultaneous ability of these macrophages to kill Nocardia asteroides.
Main Methods:
- Macrophages (peritoneal, alveolar, splenic, Kupffer cells) from normal and immunized mice were infected with Nocardia asteroides in vitro.
- Uptake and killing assays were performed.
- Acid phosphatase levels and intracellular Nocardia numbers were quantified using a computer-assisted cytophotometry system.
Main Results:
- Acid phosphatase activity decreased with increasing intracellular Nocardia in non-killing macrophages.
- Activity remained unchanged in macrophages that inhibited but did not kill Nocardia.
- Activity increased in macrophages that effectively killed Nocardia.
- Macrophage nocardicidal effectiveness varied by anatomical site and immunization status, with corresponding differences in acid phosphatase activity response.
Conclusions:
- Lysosomal acid phosphatase activity serves as a reliable marker for macrophage capacity to inhibit growth and kill Nocardia asteroides.
- Functional differences in nocardicidal and acid phosphatase activities exist among macrophages from different anatomical locations and between normal and immunized states.