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Stimulation of monocyte precursors in vivo by an extract from Listeria monocytogenes
Abstract:
A water-soluble monocytosis-producing activity (MPA) extracted from Listeria monocytogenes was found to stimulate proliferation of promonocytes in vivo. Mice were pulse-labelled for 2 h with tritiated thymidine ([3H]TdR) at various times after intraperitoneal injection of MPA. Autoradiography of bone marrow cells revealed an increased labelling index of promonocytes of MPA-treated mice which was maximum 8 h after the MPA injection. Mice labelled with [3H]TdR 8 h after MPA injection developed a monocytosis at the expected time (peak at 48 h) and the blood monocytes were found to be highly labelled. Both the generation time of monocyte precursors and the halftime of blood monocytes were found to be shorter than the corresponding values in control mice.
Insights
A Listeria monocytogenes extract stimulated monocyte production in mice. This monocytosis-producing activity (MPA) accelerated the generation of monocyte precursors and reduced the lifespan of blood monocytes.
Area of Science:
- Immunology
- Microbiology
- Hematology
Background:
- Listeria monocytogenes produces monocytosis-producing activity (MPA).
- MPA is a water-soluble extract that stimulates promonocyte proliferation.
- The in vivo effects of MPA on monocyte kinetics are not fully understood.
Purpose of the Study:
- To investigate the effect of MPA on monocyte production and kinetics in mice.
- To determine the impact of MPA on promonocyte proliferation and blood monocyte turnover.
Main Methods:
- Mice were injected with MPA and pulse-labelled with tritiated thymidine ([3H]TdR).
- Autoradiography of bone marrow cells assessed promonocyte proliferation.
- Blood monocyte labeling and kinetics were analyzed over time.
Main Results:
- MPA significantly increased the labeling index of promonocytes, peaking 8 hours post-injection.
- Mice treated with MPA exhibited monocytosis with highly labeled blood monocytes.
- MPA shortened both the generation time of monocyte precursors and the half-life of blood monocytes compared to controls.
Conclusions:
- MPA stimulates promonocyte proliferation and accelerates monocyte production in vivo.
- MPA influences monocyte kinetics, leading to increased monocyte numbers and altered turnover rates.
- These findings provide insights into the immunomodulatory effects of Listeria monocytogenes components.