title: IL-15 regulates CD8+ T cell contraction during primary infection.
abstract: During the course of acute infection with an intracellular pathogen, Ag-specific T cells proliferate in the expansion phase, and then most of the T cells die by apoptosis in the following contraction phase, but the few that survive become memory cells and persist for a long period of time. Although IL-15 is known to play an important role in long-term maintenance of memory CD8+ T cells, the potential roles of IL-15 in CD8+ T cell contraction are not known. Using an adoptive transfer system of OT-I cells expressing OVA257-264/Kb-specific TCR into control, IL-15 knockout (KO) and IL-15 transgenic (Tg) mice followed by challenge with recombinant Listeria monocytogenes expressing OVA, we found that the survival of CD44+CD62L-CD127- effector OT-I cells during the contraction phase is critically dependent on IL-15. In correlation with the expression level of Bcl-2 in OT-I cells, the number of OT-I cells was markedly reduced in IL-15 KO mice but remained at a high level in IL-15 Tg mice during the contraction phase, compared with control mice. In vivo administration of rIL-15 during the contraction phase in IL-15 KO mice inhibited the contraction of effector OT-I cells accompanied by up-regulation of Bcl-2 expression. Furthermore, enforced expression of Bcl-2 protected the majority of effector OT-I cells from death in IL-15 KO mice after infection. These results suggest that IL-15 plays a critical role in protecting effector CD8+ T cells from apoptosis during the contraction phase following a microbial infection via inducing antiapoptotic molecules.
authors.affiliation: Division of Host Defense, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan. yajimato@bioreg.kyushu-u.ac.jp
authors.forename: Toshiki
authors.initials: T
authors.lastname: Yajima
authors.forename: Kazufumi
authors.initials: K
authors.lastname: Yoshihara
authors.forename: Kenji
authors.initials: K
authors.lastname: Nakazato
authors.forename: Shino
authors.initials: S
authors.lastname: Kumabe
authors.forename: Shigeo
authors.initials: S
authors.lastname: Koyasu
authors.forename: Subash
authors.initials: S
authors.lastname: Sad
authors.forename: Hao
authors.initials: H
authors.lastname: Shen
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kuwano
authors.forename: Yasunobu
authors.initials: Y
authors.lastname: Yoshikai
mesh_terms: D019264:Adoptive Transfer; D000818:Animals; D017209:Apoptosis / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D002470:Cell Survival / Q000276:immunology; D004527:Egg Proteins / Q000276:immunology; D005434:Flow Cytometry; D007156:Immunologic Memory; D019409:Interleukin-15 / Q000276:immunology*; D008089:Listeria monocytogenes / Q000276:immunology; D008088:Listeriosis / Q000276:immunology*; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D010047:Ovalbumin / Q000276:immunology; D010446:Peptide Fragments; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000276:immunology
chemical_list: D004527:Egg Proteins; D019409:Interleukin-15; C110366:OVA-8; D010446:Peptide Fragments; D019253:Proto-Oncogene Proteins c-bcl-2; D011948:Receptors, Antigen, T-Cell; D010047:Ovalbumin