IL-15 promotes the survival of naive and memory phenotype CD8+ T cells.
IL-15 stimulates the proliferation of memory phenotype CD44(high)CD8(+) T cells and is thought to play a key role in regulating the turnover of these cells in vivo. We have investigated whether IL-15 also has the capacity to affect the life span of naive phenotype (CD44(low)) CD8(+) T cells. We report that IL-15 promotes the survival of both CD44(low) and CD44(high) CD8(+) T cells, doing so at much lower concentrations than required to induce proliferation of CD44(high) cells. Rescue from apoptosis was associated with the up-regulation of Bcl-2 in both cell types, whereas elevated expression of Bcl-x(L) was observed among CD44(high) but not CD44(low) CD8(+) cells. An investigation into the role of IL-15R subunits in mediating the effects of IL-15 revealed distinct contributions of the alpha- and beta- and gamma-chains. Most strikingly, IL-15R alpha was not essential for either induction of proliferation or promotion of survival by IL-15, but did greatly enhance the sensitivity of cells to low concentrations of IL-15. By contrast, the beta- and gamma-chains of the IL-15R were absolutely required for the proliferative and pro-survival effects of IL-15, although it was not necessary for CD44(high)CD8(+) cells to express higher levels of IL-15R beta than CD44(low) cells to proliferate in response to IL-15. These results show that IL-15 has multiple effects on CD8 T cells and possesses the potential to regulate the life span of naive as well as memory CD8(+) T cells.
Edward Jenner Institute for Vaccine Research, Compton, Newbury, Berkshire, United Kingdom.
Marion
M
Berard
Katja
K
Brandt
Silvia
S
Bulfone-Paus
David F
DF
Tough
D000818:Animals; D017209:Apoptosis / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism*; D002455:Cell Division / Q000276:immunology; D002470:Cell Survival / Q000276:immunology; D002478:Cells, Cultured; D004306:Dose-Response Relationship, Immunologic; D018960:Hyaluronan Receptors / Q000096:biosynthesis; D007156:Immunologic Memory / Q000276:immunology*; D016130:Immunophenotyping; D019409:Interleukin-15 / Q000378:metabolism / Q000494:pharmacology*; D007399:Interphase / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D021122:Protein Subunits / Q000096:biosynthesis / Q000502:physiology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D053647:Receptors, Interleukin-15; D015375:Receptors, Interleukin-2 / Q000096:biosynthesis / Q000502:physiology; D016176:T-Lymphocyte Subsets / Q000276:immunology* / Q000378:metabolism*; D015854:Up-Regulation / Q000276:immunology; D051020:bcl-X Protein
C494812:Bcl2l1 protein, mouse; D018960:Hyaluronan Receptors; C508025:Il15ra protein, mouse; D019409:Interleukin-15; D021122:Protein Subunits; D019253:Proto-Oncogene Proteins c-bcl-2; D053647:Receptors, Interleukin-15; D015375:Receptors, Interleukin-2; D051020:bcl-X Protein