Related Experiment Videos
Time course of antilisterial activity by immunologically activated murine peritoneal macrophages
Abstract:
Murine peritoneal macrophages were rapidly rendered listericidal after exposure to lymphokine-rich supernatants (LRSs) derived from antigen-pulsed Listeria monocytogenes-immune spleen cells. A 6-h incubation period with LRSs was sufficient to induce microbicidal activity in resident macrophages. In vitro induction of macrophage listericidal activity by constant exposure to LRSs persisted for 18 h, after which time spleen cell factors were no longer capable of modifying intracellular inactivation of Listeria. Results obtained by utilizing a short assay indicated that the killing kinetics is extremely rapid, with large numbers of bacteria destroyed during the first 15 min of infection. Intracellular killing at this time appeared to be greatly dependent upon the stage of growth from which the microorganisms were harvested. Induction of bactericidal macrophages by infection of mice with a sublethal dose of virulent Listeria cells and subsequent intraperitoneal elicitation with heat-killed homologous bacteria was similarly a transient event. Macrophages harvested 18 h after antigenic challenge displayed dramatic antibacterial activity during the first 22 h in culture. After 22 h, activity was lost, and stasis was observed during the ensuing 23 h. At 68 h, macrophages were devoid of antilisterial action. Activity, however, could be recalled after incubation with LRSs.
Insights
Macrophages exposed to lymphokine-rich supernatants (LRSs) rapidly become listericidal, killing Listeria monocytogenes effectively. This induced antimicrobial activity is transient, lasting approximately 18-22 hours before diminishing.
Area of Science:
- Immunology
- Microbiology
Background:
- Macrophages are key immune cells involved in phagocytosis and killing of pathogens.
- Listeria monocytogenes is a facultative intracellular bacterium that can cause severe infections.
Purpose of the Study:
- To investigate the induction and duration of listericidal activity in murine peritoneal macrophages.
- To understand the kinetics of intracellular killing of Listeria monocytogenes by activated macrophages.
Main Methods:
- Macrophages were incubated with lymphokine-rich supernatants (LRSs) from Listeria monocytogenes-immune spleen cells.
- Macrophage listericidal activity was assessed by measuring the killing of Listeria monocytogenes over time.
- In vivo activation of macrophages was achieved by infecting mice and subsequent elicitation.
Main Results:
- A 6-hour incubation with LRSs was sufficient to induce rapid listericidal activity in macrophages.
- Induced macrophage antimicrobial activity persisted for 18 hours in vitro and 22 hours in vivo.
- Killing kinetics were rapid, with significant bacterial destruction within the first 15 minutes of infection.
- Macrophage activity could be recalled after subsequent incubation with LRSs.
Conclusions:
- Lymphokine-rich supernatants can transiently induce potent listericidal activity in macrophages.
- The duration of induced macrophage antimicrobial function is limited.
- Further exposure to LRSs can restore macrophage bactericidal capacity.