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Updated: May 17, 2026
Phenotypic Analysis of Rodent Malaria Parasite Asexual and Sexual Blood Stages and Mosquito Stages
Published on: May 30, 2019
Age-related susceptibility and resistance to nonlethal Plasmodium yoelii infection in C57BL/6 mice
Ying Shan1, Jun Liu, Yong-Jun Jiang
1Department of Immunology, College of Basic Medical Sciences, China Medical University, No. 92 Beier Road, Heping District, Shenyang 110001, China.
Insights
Middle-aged mice show enhanced resistance to Plasmodium yoelii infection compared to young mice, due to robust immune responses. This study reveals age-dependent differences in malaria immunity.
Area of Science:
- Immunology
- Parasitology
- Gerontology
Background:
- Children experience high malaria morbidity and mortality.
- Age-dependent immune responses influence malaria susceptibility.
Purpose of the Study:
- To analyze age-dependent immune mechanisms against malaria.
- To compare immune responses to Plasmodium yoelii 17XNL in young versus middle-aged mice.
Main Methods:
- Used young (3-week) and middle-aged (8-month) C57BL/6 mice.
- Infected mice with Plasmodium yoelii 17XNL.
- Analyzed cellular immunity, including dendritic cells, B cells, and regulatory T cells.
- Measured cytokine profiles (IFN-gamma, IL-4, IL-10) and nitric oxide (NO).
Main Results:
- Young mice showed 100% mortality and higher parasitemia.
- Middle-aged mice cleared parasites and survived, indicating resistance.
- Middle-aged mice had increased splenic myeloid dendritic cells and maturation markers.
- Upregulated IgG1/IgG2a B cells, distinct regulatory T cell dynamics, and elevated IL-4 in middle-aged mice.
- IFN-gamma and NO increased in both groups; IL-10 correlated with regulatory T cells.
Conclusions:
- Age significantly impacts malaria resistance.
- Middle-aged mice exhibit superior immune responses, including Th1/Th2 balance and regulatory T cell function.
- Effective Th1/Th2 responses and regulatory T cell activity are crucial for malaria survival.
Abstract:
In cases of human malaria, children suffer very high rates of morbidity and mortality. To analyse the mechanisms involved in age-dependent protection against malaria, we investigated the characterization of immune responses to Plasmodium yoelii 17XNL (P.y 17XNL) in young (3 weeks) and middle-aged (8 months) C57BL/6 mice. In this study, we found that 100% of young mice succumbed to P.y 17XNL infection with higher parasitemia, while middle-aged mice were able to clear blood parasites and no mortality was observed. These observations suggested that the young C57BL/6 mice were susceptible to P.y 17XNL infection, whereas the middle-aged mice were resistant. Cellular analysis revealed that both the numbers of splenic myeloid dendritic cells (mDCs) as well as the expression of DC maturation markers were higher in middle-aged mice than those in young mice. The numbers of IgG1- or IgG2a-secreting B cells increased markedly in middle-aged mice after infection with P.y 17XNL. The dynamic change of the number of CD4+CD25+Foxp3+ regulatory T cells (Tregs) in mice infected with P.y 17XNL was also different between the two groups. In addition, the levels of IFN-gamma and NO increased in both groups during early parasite infection, while there was also an obvious increase in IL-4 production in the infected middle-aged mice. The change in IL-10 levels following infection was consistent with that of the change in the number of Tregs. The survival of middle-aged mice following P.y 17XNL infection was dependent upon the establishment of effective Thl and Th2 responses and a successful switch between Th1 and Th2 responses, as well as appropriate functioning of Tregs.
