title: Generation and growth of CD28nullCD8+ memory T cells mediated by IL-15 and its induced cytokines.
abstract: Accumulation of CD28(null)CD8+ T cells and the defects of these cells in response to antigenic stimulation are the hallmarks of age-associated decline of T cell function. However, the mechanism of these age-associated changes is not fully understood. In this study, we report an analysis of the growth of human CD28(null) and CD28+CD8+ memory T cells in response to homeostatic cytokine IL-15 in vitro. We showed that 1) there was no proliferative defect of CD28(null)CD8+ memory T cells in response to IL-15 compared with their CD28+ counterparts; 2) stable loss of CD28 expression occurred in those actively dividing CD28+CD8+ memory T cells responding to IL-15; 3) the loss of CD28 was in part mediated by TNF-alpha that was induced by IL-15; and 4) CCL4 (MIP-1beta), also induced by IL-15, had a significant inhibitory effect on the growth of CD28(null) cells, which in turn down-regulated their expression of CCL4 receptor CCR5. Together, these findings demonstrate that CD28(null)CD8+ memory T cells proliferate normally in response to IL-15 and that IL-15 and its induced cytokines regulate the generation and growth of CD28(null)CD8+ T cells, suggesting a possible role of IL-15 in the increase in CD28(null)CD8+ T cells that occurs with aging.
authors.affiliation: Laboratory of Immunology, National Institute on Aging, National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA.
authors.forename: Wai Kan
authors.initials: WK
authors.lastname: Chiu
authors.forename: Monchou
authors.initials: M
authors.lastname: Fann
authors.forename: Nan-ping
authors.initials: NP
authors.lastname: Weng
mesh_terms: D000375:Aging; D018106:CD28 Antigens / Q000276:immunology* / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D049109:Cell Proliferation; D016207:Cytokines / Q000276:immunology; D006801:Humans; D007156:Immunologic Memory; D019409:Interleukin-15 / Q000276:immunology* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D018106:CD28 Antigens; D016207:Cytokines; D019409:Interleukin-15