Enhancement of virus-specific expansion of transgenic CD8 T cells in aged mice by dendritic cells

Abstract

Aging is associated with a decreased CD8 T cell response to multiple antigens and to virus infection. Although both intrinsic and extrinsic factors have been shown to contribute to the decrease, the mechanisms are still largely unknown. In this study, the role of dendritic cells (DCs) in the age-associated decrease was examined. Influenza-specific TCR transgenic CD8 T cells of young mice demonstrated limited expansion in response to influenza infection when adoptively transferred to aged compared to young mice. This decreased response in aged mice could be significantly enhanced when DCs of young mice were co-transferred. Co-transfer of DCs had no impact in young recipient mice. Adoptive transfer of the DCs also increased the endogenous CD8 T cell response of intact aged mice, although to a lesser degree. These results suggest that the diminished CD8 T cell response to virus infection in aged mice is partially attributable to age-associated changes in DCs.

FIG. 1

Enhancement of limited expansion of TCR Tg CD8 T cells in aged mice by DCs. 1×10⁴ purified CD8 T cells from spleens of Clone-4 mice (Thy1.1⁺) were adoptively transferred or co-transferred with CD11c⁺ cells of young BALB/c mice (1×10⁶/mouse) into congenic young and aged mice (Thy1.2⁺). Recipient mice were infected i.v. with PR8 6 h after transfer. On Day 4 post-infection, splenocytes were isolated and stained with antibodies to CD8, CD44, and Thy1.1. Tg CD8 T cells were identified by Thy1.1⁺CD44^high staining after gating on total CD8 T cells. The function of the specific CD8 T cells was examined by intracellular IFN-γ staining after in vitro stimulation with HA_518–526 peptide for 5 h. (A) Percentages of donor Tg CD8 T cells (Thy1.1⁺) of total CD8⁺ cells, and absolute numbers of CD8⁺Thy1.1⁺ cells. (B) Percentages of Thy1.1⁺IFN-γ⁺ cells gated on CD8⁺ cells, and absolute numbers of Thy1.1⁺IFN-γ⁺ cells. Each plot is representative of one mouse with numbers reflecting ± SD of 3–4 mice. * p < 0.05. Results are representative of three independent experiments with similar results.

FIG. 2

DCs enhance the response of a large number of Tg CD8 T cells in aged mice. Similar to Fig.1, except: 1) 1×10⁶ purified CD8 T cells from spleens of Clone-4 mice were adoptively transferred; and 2) splenocytes were isolated on Day 3 post-infection. (A) Percentages of Tg CD8 T cells of total CD8⁺ cells, and absolute numbers of CD8⁺Thy1.1⁺ cells. (B) Percentages of Thy1.1⁺IFN-γ⁺ cells gated on total CD8⁺ cells, and absolute numbers of Thy1.1⁺IFN-γ⁺ cells after in vitro stimulation with HA_518–526 peptide. Each plot is representative of one mouse with numbers reflecting ± SD of 3–4 mice. * p < 0.05. The experiment was performed three times with similar results.

FIG. 3

DCs provide limited enhancement of endogenous CD8 T cell response in aged mice. Enriched CD11c⁺ cells of spleens of young BALB/c mice (1×10⁶/mouse) were adoptively transferred into aged congenic mice. Mice were infected i.v. with PR8 6 h later. On Day 10 post infection, splenocytes were isolated, stained with CD8, CD44, and K^d-HA_518–526 tetramer, and assessed by flow cytometry. Tetramer⁺/CD44^high cells are presented as percent (A), and absolute number (B) of total CD8 T cells. Each plot shows CD8 T cells from one representative mouse with numbers indicating mean ± SD of 3–4 mice. * p < 0.05. Data are representative of four independent experiments with similar results.