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Akira Motegi, Manabu Kinoshita, Akihito Inatsu, Yoshiko Habu, Daizoh Saitoh, Shuhji Seki, IL-15-induced CD8+CD122+ T cells increase antibacterial and anti-tumor immune responses: implications for immune function in aged mice, Journal of Leukocyte Biology, Volume 84, Issue 4, Oct 2008, Pages 1047–1056, https://doi.org/10.1189/jlb.0807530
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Abstract
We previously proposed that mouse CD8+CD122+ T cells and human CD57+ T cells, which increase with age and exhibit potent IFN-γ production, represent a double-edged sword as they play critical roles in host defense and the lethal IL-12/LPS-induced generalized Shwartzman reaction (GSR). However, our proposal was based solely on comparisons of young and old mice. In this study, we attempted to increase CD8+CD122+ T cells in young mice with exogenous IL-15 and confirm their countervailing functions in young mice. After young mice (6 weeks) were injected with IL-15, they showed significant increases in CD8+CD122+ T cells in the liver and spleen. Liver CD8+CD122+ T cells from IL-15-pretreated mice had a potent capacity to produce IFN-γ after IL-12 injection or Escherichia coli infection. IL-15-pretreated mice showed increased survival to E. coli infections and enhanced anti-tumor activities against liver metastatic EL4 cells, as well as an exacerbation of the GSR. Correspondingly, liver CD8+CD122+ T cells produced more perforin than CD8+CD122− T cells in EL4-inoculated mice. Unexpectedly, comparable IL-15 treatment did not induce further increases in CD8+CD122+ T cells in aged mice and did not enhance their defenses against bacterial infection or tumor growth. Interestingly, however, nontreated, aged mice (50 weeks) showed twofold higher IL-15 levels (but not TNF or IFN-γ) in liver homogenates compared with young mice. Our results further support that CD8+CD122+ T cells, which are increased physiologically or therapeutically by IL-15, are involved in antibacterial immunity, anti-tumor immunity, and the GSR.
