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Low response of BALB/c macrophages to priming and activating signals
1URA CNRS 1116, Université Paris-Sud, Orsay, France.
Abstract:
Trehalose dimycolate (TDM), a mycobacterial glycolipid, is a powerful macrophage-priming agent. However, its efficiency seems limited in the case of BALB/c mice. Peritoneal macrophages harvested from TDM-treated BALB/c mice did not control BCG growth in vitro as efficiently as similar macrophages from two other mouse strains, (B6 x D2)F1 and C57BL/6, which are respectively Bcgr and Bcgs. BALB/c macrophages elicited by TDM also exhibited a low capacity to produce hydrogen peroxide and, after activation by lipopolysaccharide (LPS), weak cytostatic activity against P815 mastocytoma cells. Finally, alkaline phosphodiesterase, a marker of resident and inflammatory macrophages, was still expressed at a high level in macrophages of BALB/c mice treated with TDM. Low responsiveness of BALB/c macrophages to stimuli was not observed with TDM only; activation for tumor cytotoxicity of thioglycolate-elicited macrophages from BALB/c mice required also higher doses of interferon-gamma, and LPS. L-Arginine-dependent production of nitric oxide was inducible in macrophages from BALB/c mice, but the conditions required for its induction were more stringent. Thus, the reduced antiproliferative effects of BALB/c macrophages may be due to uncomplete induction of NO synthase after suboptimal stimulation.
Insights
Trehalose dimycolate (TDM) primes macrophages but is less effective in BALB/c mice. These macrophages show reduced control of BCG growth and lower responses to stimuli like LPS, potentially due to incomplete nitric oxide synthase induction.
Area of Science:
- Immunology
- Microbiology
- Glycolipid Research
Background:
- Trehalose dimycolate (TDM), a mycobacterial glycolipid, is recognized for its potent macrophage-priming capabilities.
- Previous studies suggest varying host responses to TDM, necessitating investigation into strain-specific efficacies.
Purpose of the Study:
- To investigate the differential responsiveness of BALB/c mouse macrophages to Trehalose dimycolate (TDM) compared to other mouse strains.
- To elucidate the underlying mechanisms contributing to the observed reduced efficacy of TDM in BALB/c mice.
Main Methods:
- Harvesting peritoneal macrophages from TDM-treated BALB/c, (B6xD2)F1, and C57BL/6 mice.
- Assessing macrophage control of BCG growth in vitro.
- Measuring hydrogen peroxide production and cytostatic activity against P815 mastocytoma cells after LPS activation.
- Evaluating alkaline phosphodiesterase expression.
- Investigating nitric oxide production under varying stimulation conditions.
Main Results:
- BALB/c macrophages showed significantly less control over BCG growth compared to macrophages from (B6xD2)F1 and C57BL/6 mice.
- TDM-elicited BALB/c macrophages exhibited diminished hydrogen peroxide production and weak cytostatic activity post-LPS activation.
- Alkaline phosphodiesterase, a macrophage marker, remained highly expressed in TDM-treated BALB/c macrophages.
- Induction of nitric oxide production in BALB/c macrophages required more stringent conditions, suggesting incomplete nitric oxide synthase activation.
Conclusions:
- BALB/c mice display a reduced responsiveness to the macrophage-priming effects of Trehalose dimycolate (TDM).
- The diminished antiproliferative capacity of BALB/c macrophages may stem from incomplete induction of nitric oxide synthase following suboptimal stimulation.
- These findings highlight the importance of host genetic background in modulating immune responses to mycobacterial glycolipids like TDM.