title: IL-7 administration alters the CD4:CD8 ratio, increases T cell numbers, and increases T cell function in the absence of activation.
abstract: IL-7 is vital for the development of the immune system and profoundly enhances the function of mature T cells. Chronic administration of IL-7 to mice markedly increases T cell numbers, especially CD8(+) T cells, and enhances T cell functional potential. However, the mechanism by which these effects occur remains unclear. This report demonstrates that only 2 days of IL-7 treatment is needed for maximal enhancement of T cell function, as measured by proliferation, with a 6- to 12-fold increase in the proportion of CD4(+) and CD8(+) T cells in cell cycle by 18 h of ex vivo stimulation. Moreover, a 2-day administration of IL-7 in vivo increases basal proliferation by 4- and 14-fold in CD4(+) and CD8(+) T cells, respectively. These effects occur in the absence of cytokine production, increases in most activation markers, and changes in memory markers. This enhanced basal proliferation is the basis for the increase in T cell numbers in that IL-7 induces an additional 60% and 85% of resting CD4(+) and CD8(+) T cells, respectively, to enter cell cycle in mice given IL-7 for 7 days. These results demonstrate that in vivo administration of IL-7 increases T cell numbers and functional potential via a homeostatic, nonactivating process. These findings may suggest a unique clinical niche for IL-7 in that IL-7 therapy may increase T cell numbers and enhance responses to specific antigenic targets while avoiding a general, nonspecific activation of the T cell population.
authors.affiliation: Laboratory of Experimental Immunology, Division of Basic Sciences, National Cancer Institute-Frederick Cancer Research and Development Center, Frederick, MD 21702, USA.
authors.forename: L A
authors.initials: LA
authors.lastname: Geiselhart
authors.forename: C A
authors.initials: CA
authors.lastname: Humphries
authors.forename: T A
authors.initials: TA
authors.lastname: Gregorio
authors.forename: S
authors.initials: S
authors.lastname: Mou
authors.forename: J
authors.initials: J
authors.lastname: Subleski
authors.forename: K L
authors.initials: KL
authors.lastname: Komschlies
mesh_terms: D000818:Animals; D000945:Antigens, Differentiation, T-Lymphocyte / Q000096:biosynthesis; D016516:CD4-CD8 Ratio; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D002453:Cell Cycle / Q000276:immunology; D002478:Cells, Cultured; D016207:Cytokines / Q000096:biosynthesis; D004306:Dose-Response Relationship, Immunologic; D004334:Drug Administration Schedule; D007156:Immunologic Memory; D007274:Injections, Intraperitoneal; D015851:Interleukin-7 / Q000008:administration & dosage*; D007552:Isotonic Solutions / Q000008:administration & dosage; D008198:Lymph Nodes / Q000166:cytology / Q000276:immunology; D008213:Lymphocyte Activation; D018655:Lymphocyte Count; D051379:Mice; D020297:Mice, Congenic; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016176:T-Lymphocyte Subsets / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism; D015854:Up-Regulation / Q000276:immunology*
chemical_list: D000945:Antigens, Differentiation, T-Lymphocyte; D016207:Cytokines; C072670:Hanks Balanced Salt Solution; D015851:Interleukin-7; D007552:Isotonic Solutions