Enhancement of proliferation and downregulation of TRAIL expression on CD8+ T cells by IL-21.
Mounting evidence indicates that the cytokine IL-21 can significantly enhance the survival of CD8(+) T lymphocytes. Given that CD4(+) T lymphocytes constitute the main cellular source for IL-21 in vivo, it is tempting to speculate a direct role in mediating the "help" provided by these CD4(+) T cells to the CD8 response. A new report in this issue of the European Journal of Immunology advances this notion by showing that CD8(+) T cells lacking the IL-21 receptor phenocopy those primed in the absence of CD4(+) T cells (the so-called "helpless" CD8(+) T cells) in their induction of the pro-apoptotic factor TRAIL. This finding helps to define the role of IL-21 in the CD8 response, and raises new questions relevant for achieving a broader understanding of this multifunctional cytokine.
Department of Immunohematology, Leiden University Medical Center, Leiden, The Netherlands. C.Melief@lumc.nl
Cornelis J M
CJ
Melief
Stephen P
SP
Schoenberger
D000818:Animals; D017209:Apoptosis / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D049109:Cell Proliferation; D002470:Cell Survival / Q000276:immunology; D015536:Down-Regulation / Q000276:immunology*; D006801:Humans; D007378:Interleukins / Q000276:immunology* / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000096:biosynthesis / Q000276:immunology*; D000098546:Interleukin-21
D007378:Interleukins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D000098546:Interleukin-21