title: Age-related susceptibility and resistance to nonlethal Plasmodium yoelii infection in C57BL/6 mice.
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.
authors.affiliation: Department of Immunology, College of Basic Medical Sciences, China Medical University, No. 92 Beier Road, Heping District, Shenyang 110001, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Shan
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.forename: Yong-Jun
authors.initials: YJ
authors.lastname: Jiang
authors.forename: Hong
authors.initials: H
authors.lastname: Shang
authors.forename: Dong
authors.initials: D
authors.lastname: Jiang
authors.forename: Ya-Ming
authors.initials: YM
authors.lastname: Cao
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D001402:B-Lymphocytes; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D004198:Disease Susceptibility / Q000276:immunology*; D005260:Female; D005786:Gene Expression Regulation / Q000276:immunology; D007074:Immunoglobulin G / Q000145:classification / Q000378:metabolism; D007371:Interferon-gamma / Q000378:metabolism; D008288:Malaria / Q000276:immunology / Q000662:veterinary*; D051379:Mice; D009569:Nitric Oxide / Q000378:metabolism; D018512:Parasitemia; D010967:Plasmodium yoelii / Q000502:physiology*; D013154:Spleen / Q000166:cytology
chemical_list: D016207:Cytokines; D007074:Immunoglobulin G; D009569:Nitric Oxide; D007371:Interferon-gamma