title: IL-15 as a mediator of CD4+ help for CD8+ T cell longevity and avoidance of TRAIL-mediated apoptosis.
abstract: CD4+ helper T cells contribute to the induction and maintenance of antigen-specific CD8+ T cells. Their absence results in short-lived antigen-specific CD8+ T cells and defective secondary CD8+ T cell responses because of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis. Here, we show that IL-15 codelivered with vaccines can overcome CD4+ T cell deficiency for promoting longevity of antigen-specific CD8+ T cells and avoidance of TRAIL-mediated apoptosis. In both priming and secondary responses, IL-15 down-regulates proapoptotic Bax, an intermediate in TRAIL-mediated apoptosis, and increases anti-apoptotic Bcl-X(L) in CD8+ T cells. Thus, IL-15 is sufficient to mimic CD4+ T cell help. Antigen-specific CD4+ T cells induce dendritic cells (DCs) to produce IL-15. IL-15 is also necessary for optimal help, because helper cells do not deliver effective help through IL-15-/- DCs. Therefore, IL-15 codelivered with vaccines can overcome CD4+ helper T cell deficiency for induction of functionally efficient CD8+ T cells and maintenance of CD8+ cytotoxic T lymphocytes (CTLs), and IL-15 is probably one of the natural mediators of help. These findings suggest new vaccine strategies against infections and cancers, especially in individuals with CD4-deficiency.
authors: Vaccine Branch and Metabolism Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-1578, USA.
authors: Sangkon
authors: S
authors: Oh
authors: Liyanage P
authors: LP
authors: Perera
authors: Masaki
authors: M
authors: Terabe
authors: Ling
authors: L
authors: Ni
authors: Thomas A
authors: TA
authors: Waldmann
authors: Jay A
authors: JA
authors: Berzofsky
mesh_terms: D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology; D017209:Apoptosis / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism*; D053148:Caspase 3 / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D003713:Dendritic Cells / Q000276:immunology / Q000378:metabolism; D015536:Down-Regulation; D005260:Female; D007156:Immunologic Memory / Q000276:immunology; D019409:Interleukin-15 / Q000172:deficiency / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009369:Neoplasms / Q000276:immunology / Q000473:pathology; D011485:Protein Binding; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism*; D015854:Up-Regulation; D014612:Vaccines / Q000276:immunology; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: D019409:Interleukin-15; D053221:TNF-Related Apoptosis-Inducing Ligand; D014612:Vaccines; D051028:bcl-2-Associated X Protein; D053148:Caspase 3