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Induction of interleukin 1 by Legionella pneumophila in murine peritoneal macrophage cultures
R H Widen1, T W Klein, C A Newton
1University of South Florida College of Medicine, Tampa.
Abstract:
Legionella pneumophila-induced production of both membrane-associated and secreted interleukin 1 (mIL-1 and sIL-1, respectively) was examined utilizing peritoneal macrophages from BALB/c mice. The Legionella preparations for these studies included viable bacteria and formalin-killed whole cell preparations. Both of the preparations induced mIL-1 and sIL-1 in a dose-dependent fashion. However, the viable bacteria required about 1 log lower concentrations than the formalin-killed bacteria to induce the same level of IL-1 activity measured in the thymocyte proliferation assay. Kinetic studies showed that mIL-1 and sIL-1 were detectable within 4 hr after addition of either of the L. pneumophila preparations to the peritoneal macrophage cultures, with peak levels achieved within 24 hr. These results indicate that L. pneumophila is a potent inducer of both mIL-1 and sIL-1 in normal mouse peritoneal macrophage cultures.
Insights
Legionella pneumophila potentl y induces both membrane-associated interleukin 1 (mIL-1) and secreted interleukin 1 (sIL-1) in mouse macrophages. Both viable and killed bacteria stimulated IL-1 production in a dose-dependent manner.
Area of Science:
- Immunology
- Microbiology
Background:
- Interleukin 1 (IL-1) plays a crucial role in immune responses.
- Legionella pneumophila is a bacterial pathogen known to cause pneumonia.
Purpose of the Study:
- To investigate the induction of membrane-associated IL-1 (mIL-1) and secreted IL-1 (sIL-1) by Legionella pneumophila.
- To compare the potency of viable versus formalin-killed L. pneumophila in inducing IL-1 production.
Main Methods:
- Peritoneal macrophages from BALB/c mice were cultured with L. pneumophila preparations (viable and formalin-killed).
- Interleukin 1 activity was measured using a thymocyte proliferation assay.
- Kinetic studies were performed to determine the time course of IL-1 production.
Main Results:
- Both viable and formalin-killed L. pneumophila induced mIL-1 and sIL-1 in a dose-dependent manner.
- Viable bacteria were approximately 1 log more potent than killed bacteria in inducing IL-1.
- IL-1 production was detectable within 4 hours and peaked within 24 hours.
Conclusions:
- L. pneumophila is a potent inducer of both mIL-1 and sIL-1 in mouse peritoneal macrophages.
- The study highlights the immunomodulatory effects of L. pneumophila on macrophages.