title: IL-2 is not required for the initiation of CD8 T cell cycling but sustains expansion.
abstract: Based primarily on in vitro data, IL-2 is believed to be the key cytokine for initiation of the cell cycle of activated T cells. However, the role of IL-2 remains unresolved for T cell responses in vivo. We examined whether the absence of IL-2-mediated signaling in CD8 T cells affected initiation of proliferation. Our results conclusively demonstrated that initial division of Ag-specific CD8 T cells following priming was IL-2 independent, regardless of the context in which Ag was presented. In contrast, the latter stage of the proliferative phase was IL-2-dependent, particularly in nonlymphoid tissues. Thus, activated CD8 T cells initially undergo IL-2-independent proliferation, but reach a critical juncture where the requirement for IL-2 as a growth factor gains prominence.
authors.affiliation: Department of Medicine, Division of Immunology, University of Connecticut Health Center, Farmington, CT 06030, USA.
authors.forename: Warren N
authors.initials: WN
authors.lastname: D'Souza
authors.forename: Leo
authors.initials: L
authors.lastname: Lefrançois
mesh_terms: D000818:Animals; D000951:Antigens, Neoplasm / Q000008:administration & dosage / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology* / Q000276:immunology* / Q000473:pathology / Q000821:virology; D002453:Cell Cycle / Q000276:immunology*; D002455:Cell Division / Q000276:immunology; D045744:Cell Line, Tumor; D006801:Humans; D007274:Injections, Intraperitoneal; D007376:Interleukin-2 / Q000008:administration & dosage / Q000096:biosynthesis / Q000172:deficiency / Q000502:physiology*; D053645:Interleukin-2 Receptor alpha Subunit; D008198:Lymph Nodes / Q000276:immunology / Q000473:pathology / Q000821:virology; D008213:Lymphocyte Activation / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D010047:Ovalbumin / Q000008:administration & dosage / Q000276:immunology; D018123:Receptors, Interleukin / Q000096:biosynthesis / Q000502:physiology; D015375:Receptors, Interleukin-2 / Q000378:metabolism; D011994:Recombinant Proteins / Q000008:administration & dosage; D013280:Stomatitis / Q000276:immunology / Q000473:pathology; D014721:Vesicular stomatitis Indiana virus / Q000276:immunology
chemical_list: D000951:Antigens, Neoplasm; C508017:IL2RA protein, human; C508018:Il2ra protein, mouse; D007376:Interleukin-2; D053645:Interleukin-2 Receptor alpha Subunit; D018123:Receptors, Interleukin; D015375:Receptors, Interleukin-2; D011994:Recombinant Proteins; D010047:Ovalbumin