title: Defective thymic progenitor development and mature T-cell responses in a mouse model for Down syndrome.
abstract: In addition to archetypal cognitive defects, Down syndrome (DS) is characterized by altered lymphocyte development and function, including premature thymic involution and increased incidence of infections. However, the potential mechanisms for these changes have not been fully elucidated. The current study used the Ts65Dn mouse model of DS to assess deficiencies in T-cell development and possible molecular alterations. Ts65Dn mice exhibited premature thymic involution and a threefold to fourfold decrease in the number and proportion of immature, double-negative thymocyte progenitors. In addition, there were twofold fewer double-positive and CD4 single-positive thymocytes in Ts65Dn thymuses. Reflecting this deficient thymic function, there were fewer naive T cells in the spleen and polyclonal stimulation of peripheral T cells exhibited a marked reduction in proliferation, suggesting a senescent phenotype. In contrast, B-cell progenitors were unchanged in the bone marrow of Ts65Dn mice, but in the spleen, there were decreased transitional and follicular B cells and these cells proliferated less upon antigen receptor stimulus but not in response to lipopolysaccharide. As a potential mechanism for diminished thymic function, immature thymocyte populations expressed diminished levels of the cytokine receptor interleukin-7Rα, which was associated with decreased proliferation and increased apoptosis. Increased oxidative stress and inhibition of the Notch pathway were identified as possible mediators of decreased interleukin-7Rα expression in Ts65Dn mice. The data suggest that immature thymocyte defects underlie immune dysfunction in DS and that increased oxidative stress and reduced cytokine signalling may alter lymphocyte development in Ts65Dn mice.
authors: Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
authors: Laureanne P E
authors: LP
authors: Lorenzo
authors: Kristen E
authors: KE
authors: Shatynski
authors: Sarah
authors: S
authors: Clark
authors: Paul J
authors: PJ
authors: Yarowsky
authors: Mark S
authors: MS
authors: Williams
mesh_terms: D056704:Adaptive Immunity; D000818:Animals; D017209:Apoptosis; D001402:B-Lymphocytes / Q000276:immunology; D015415:Biomarkers / Q000378:metabolism; D018791:CD4 Lymphocyte Count; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D049109:Cell Proliferation; D002478:Cells, Cultured; D016922:Cellular Senescence; D004195:Disease Models, Animal; D004314:Down Syndrome / Q000235:genetics / Q000276:immunology* / Q000473:pathology; D015536:Down-Regulation; D005260:Female; D008213:Lymphocyte Activation; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D018384:Oxidative Stress; D010641:Phenotype; D020395:Receptors, Interleukin-7 / Q000378:metabolism; D051880:Receptors, Notch / Q000378:metabolism; D015398:Signal Transduction; D013154:Spleen / Q000276:immunology; D013234:Stem Cells / Q000276:immunology* / Q000473:pathology; D013950:Thymus Gland / Q000276:immunology* / Q000473:pathology
chemical_list: D015415:Biomarkers; D020395:Receptors, Interleukin-7; D051880:Receptors, Notch; C415350:interleukin-7 receptor, alpha chain
keywords: Down syndrome; interleukin-7 receptor; lymphocyte development; reactive oxygen species; thymus