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Updated: Aug 20, 2026
Depletion and Reconstitution of Macrophages in Mice
Published on: August 1, 2012
The unresponsiveness of aged mice to polysaccharide antigens is a result of a defect in macrophage function
R Lakshman Chelvarajan1, Sarah M Collins, Juliana M Van Willigen
1Department of Microbiology, Immunology and Molecular Genetics, Sanders Brown Center on Aging, University of Kentucky, Lexington, KY 40536-0230, USA.
Abstract:
A reduction in macrophage (MPhi) function with aging makes mice less responsive to bacterial capsular polysaccharides, such as those present in the pneumococcal polysaccharide vaccine, a model of thymus independent (TI) antigen (Ag). Using trinitrophenol (TNP)-lipopolysaccharide (LPS) and TNP-Ficoll, two other well-studied TI Ag, we studied the mechanistic basis of reduced MPhi function in the aged. We show that aged mice are profoundly hyporesponsive to these TI Ag. As a result of a requirement for MPhi, highly purified B cells from young-adult mice do not respond to TI Ag. When purified, young B cells were immunized with TNP-Ficoll, the antibody production from those cultures reconstituted with MPhi from aged mice was significantly lower than that seen with young MPhi. Consequently, this unresponsiveness can be overcome by a mixture of interleukin (IL)-1beta and IL-6. Upon stimulation with LPS, in comparison with young MPhi, aged MPhi secreted reduced amounts of IL-6, tumor necrosis factor alpha, IL-1beta, and IL-12, cytokines necessary for B cells to respond to TI Ag. LPS also induced aged MPhi to produce an excess of IL-10. Neutralization of IL-10 enhanced the production of proinflamatory cytokines by MPhi upon LPS stimulation and also induced Ab production by aged splenocytes. Thus, the inability of aged MPhi to help the B cell response appears to be caused by an excess of IL-10. As aged MPhi have a reduced number of cells expressing Toll-like receptor 4 and CD14, the imbalance in cytokine production might be partly a result of fewer cells expressing key components of the LPS receptor complex.
Insights
Aging impairs macrophage function, reducing immune response to vaccines. Aged macrophages produce excess IL-10, hindering B cell antibody production, which can be overcome by neutralizing IL-10.
Area of Science:
- Immunology
- Aging Research
- Cellular Biology
Background:
- Macrophage (MPhi) function declines with age, impacting immune responsiveness.
- This reduced function affects responses to thymus-independent (TI) antigens, like those in vaccines.
- Understanding these age-related changes is crucial for improving vaccine efficacy in older populations.
Purpose of the Study:
- To investigate the mechanistic basis of reduced macrophage function in aged mice.
- To determine the role of macrophages in the hyporesponsiveness to TI antigens in aging.
- To identify specific molecular factors contributing to impaired immune responses in aged individuals.
Main Methods:
- Utilized trinitrophenol (TNP)-lipopolysaccharide (LPS) and TNP-Ficoll as TI antigens in aged and young mice.
- Assessed antibody production from purified B cells reconstituted with macrophages from young and aged mice.
- Analyzed cytokine profiles (IL-6, TNF-alpha, IL-1beta, IL-12, IL-10) secreted by macrophages upon LPS stimulation.
- Investigated the effect of IL-10 neutralization on macrophage and splenocyte responses.
- Examined the expression of Toll-like receptor 4 (TLR4) and CD14 on aged macrophages.
Main Results:
- Aged mice showed profound hyporesponsiveness to TI antigens.
- Young B cells reconstituted with aged macrophages produced significantly lower antibodies compared to those with young macrophages.
- Aged macrophages secreted reduced pro-inflammatory cytokines (IL-6, TNF-alpha, IL-1beta, IL-12) and excess IL-10 upon LPS stimulation.
- Neutralization of IL-10 restored pro-inflammatory cytokine production and induced antibody production in aged splenocytes.
- Aged macrophages exhibited reduced expression of TLR4 and CD14.
Conclusions:
- An excess of IL-10 produced by aged macrophages is a key factor in their inability to support B cell responses to TI antigens.
- Reduced expression of TLR4 and CD14 on aged macrophages may contribute to the observed imbalance in cytokine production.
- These findings highlight a critical mechanism underlying age-related immune dysfunction and suggest potential therapeutic targets.
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