title: The role of B7 costimulation in CD4/CD8 T cell homeostasis.
abstract: The effect of B7-mediated costimulation on T cell homeostasis was examined in studies of B7-1 (CD80) and B7-2 (CD86) transgenic as well as B7-deficient mice. B7 overexpression in transgenic mice resulted in marked polyclonal peripheral T cell hyperplasia accompanied by skewing toward an increased proportion of CD8 single-positive cells and a decreased proportion of CD4 single-positive cells in thymus and more markedly in peripheral T cells. B7-induced T cell expansion was dependent on both CD28 and TCR expression. Transgenic overexpression of B7-1 or B7-2 resulted in down-regulation of cell surface CD28 on thymocytes and peripheral T cells through a mechanism mediated by intercellular interaction. Mice deficient in B7-1 and B7-2 exhibited changes that were the reciprocal of those observed in B7-overexpressing transgenics: a marked increase in the CD4/CD8 ratio in peripheral T cells and an increase in cell surface CD28 in thymus and peripheral T cells. These reciprocal effects of genetically engineered increase or decrease in B7 expression indicate that B7 costimulation plays a physiological role in the regulation of CD4+ and CD8+ T cell homeostasis.
authors.affiliation: Experimental Immunology Branch, National Cancer Institute, and National Institute on Aging, National Institutes of Health, Bethesda, MD 20892, USA. yux@intra.nei.nih.gov
authors.forename: X
authors.initials: X
authors.lastname: Yu
authors.forename: S
authors.initials: S
authors.lastname: Fournier
authors.forename: J P
authors.initials: JP
authors.lastname: Allison
authors.forename: A H
authors.initials: AH
authors.lastname: Sharpe
authors.forename: R J
authors.initials: RJ
authors.lastname: Hodes
mesh_terms: D000069594:Abatacept; D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D000943:Antigens, Differentiation / Q000096:biosynthesis / Q000235:genetics; D018122:B7-1 Antigen / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D051940:B7-2 Antigen; D018106:CD28 Antigens / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; 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; D060908:CTLA-4 Antigen; D015536:Down-Regulation / Q000235:genetics / Q000276:immunology; D006706:Homeostasis / Q000235:genetics / Q000276:immunology*; D006965:Hyperplasia; D018796:Immunoconjugates; D008213:Lymphocyte Activation / Q000235:genetics; D008221:Lymphoid Tissue / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D051379:Mice; D020297:Mice, Congenic; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D008822:Mice, Transgenic; D010641:Phenotype; D011948:Receptors, Antigen, T-Cell / Q000096:biosynthesis / Q000235:genetics; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000096:biosynthesis / Q000235:genetics; D016176:T-Lymphocyte Subsets / Q000276:immunology / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D000943:Antigens, Differentiation; D018122:B7-1 Antigen; D051940:B7-2 Antigen; D018106:CD28 Antigens; D060908:CTLA-4 Antigen; C497965:Cd86 protein, mouse; C556707:Ctla4 protein, mouse; D018796:Immunoconjugates; D008562:Membrane Glycoproteins; D011948:Receptors, Antigen, T-Cell; D016693:Receptors, Antigen, T-Cell, alpha-beta; D000069594:Abatacept