title: Antigen-independent changes in naive CD4 T cells with aging.
abstract: In the elderly, a dramatic shift within the CD4+ T cell population occurs, with an increased proportion having a memory phenotype with markedly decreased responsiveness. To determine what aspects of the aged phenotype are dependent upon repeated contact with antigen in the environment, we examined CD4+ cells isolated from TCR Tg mice. There is good evidence that no cross-reacting antigens for the Tg TCR recognizing pigeon cytochrome c are found in the environment of the animal, so that alterations in the Tg CD4+ cells with aging are likely to be due to antigen-independent processes. We found that in aged animals, TCR transgene(pos) CD4+ cells, although decreased in number and antigen responsiveness, maintain a naive phenotype rather than acquiring a prototypical aged memory phenotype. In contrast, the population of transgene(1o-neg) CD4+ cells increase in proportion and express the aged phenotype. Consistent with their naive status, transgene(pos) cells of aged individuals remain CD44lo CD45RBhi, secrete IL-2 and not IL-4 or IFN-gamma upon antigenic stimulation, and require co-stimulation to proliferate to anti-CD3 stimulation. These findings suggest that the aging-associated shift to CD4 cells expressing the memory phenotype is dependent on antigenic stimulation. However, the decrease in antigen responsiveness of naive transgenepos cells, as revealed by a lower secretion of IL-2 and IL-3 and a lower proliferative capacity, suggests that additional intrinsic changes occur with aging that do not depend on encounter with antigen.
authors.affiliation: Sidney Kimmel Cancer Center, San Diego, California 92121, USA.
authors.forename: P J
authors.initials: PJ
authors.lastname: Linton
authors.forename: L
authors.initials: L
authors.lastname: Haynes
authors.forename: N R
authors.initials: NR
authors.lastname: Klinman
authors.forename: S L
authors.initials: SL
authors.lastname: Swain
mesh_terms: D000375:Aging / Q000276:immunology*; D000818:Animals; D000941:Antigens / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D010856:Columbidae; D003574:Cytochrome c Group / Q000276:immunology; D006183:H-2 Antigens; D018960:Hyaluronan Receptors; D007156:Immunologic Memory; D007371:Interferon-gamma / Q000378:metabolism; D007378:Interleukins / Q000378:metabolism; D017493:Leukocyte Common Antigens; D008213:Lymphocyte Activation; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D010641:Phenotype; D011948:Receptors, Antigen, T-Cell / Q000235:genetics / Q000276:immunology; D016176:T-Lymphocyte Subsets
chemical_list: D000941:Antigens; D003574:Cytochrome c Group; D006183:H-2 Antigens; D018960:Hyaluronan Receptors; D007378:Interleukins; D011948:Receptors, Antigen, T-Cell; D007371:Interferon-gamma; D017493:Leukocyte Common Antigens