Overexpression of IL-15 in vivo increases antigen-driven memory CD8+ T cells following a microbe exposure

T Yajima, H Nishimura, R Ishimitsu… - The Journal of …, 2002 - journals.aai.org
T Yajima, H Nishimura, R Ishimitsu, T Watase, DH Busch, EG Pamer, H Kuwano, Y Yoshikai
The Journal of Immunology, 2002journals.aai.org
To elucidate potential roles of IL-15 in the maintenance of memory CD8+ T cells, we
followed the fate of Ag-specific CD8+ T cells directly visualized with MHC class I tetramers
coupled with listeriolysin O (LLO) 91–99 in IL-15 transgenic (Tg) mice after Listeria
monocytogenes infection. The numbers of LLO 91–99-positive memory CD8+ T cells were
significantly higher at 3 and 6 wk after infection than those in non-Tg mice. The LLO 91–99-
positive CD8+ T cells produced IFN-γ in response to LLO 91–99, and an adoptive transfer of …
Abstract
To elucidate potential roles of IL-15 in the maintenance of memory CD8+ T cells, we followed the fate of Ag-specific CD8+ T cells directly visualized with MHC class I tetramers coupled with listeriolysin O (LLO) 91–99 in IL-15 transgenic (Tg) mice after Listeria monocytogenes infection. The numbers of LLO 91–99-positive memory CD8+ T cells were significantly higher at 3 and 6 wk after infection than those in non-Tg mice. The LLO 91–99-positive CD8+ T cells produced IFN-γ in response to LLO 91–99, and an adoptive transfer of CD8+ T cells from IL-15 Tg mice infected with L. monocytogenes conferred a higher level of resistance against L. monocytogenes in normal mice. The CD44+ CD8+ T cells from infected IL-15 Tg mice expressed the higher level of Bcl-2. Transferred CD44+ CD8+ T cells divided more vigorously in naive IL-15 Tg mice than in non-Tg mice. These results suggest that IL-15 plays an important role in long-term maintenance of Ag-specific memory CD8+ T cells following microbial exposure via promotion of cell survival and homeostatic proliferation.
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