title: Decreased level of T cell receptor expression by Down syndrome (trisomy 21) thymocytes.
abstract: Individuals with Down syndrome (DS) have an enhanced susceptibility to viral and bacterial infections. Previous studies by our laboratory demonstrated alterations in the proportions of peripheral T cell subpopulations and decreased proliferative, interleukin-2, and antibody responses to viral and bacterial antigens in DS. These data suggested that DS lymphocytes have a diminished ability to recognize and respond to specific antigen. It has been proposed that the abnormalities in T cell function in DS may be a result of aberrant T cell maturation within the DS thymus. Therefore, we examined by immunofluorescence and flow cytometry the cell surface expression of the alpha,beta chains of the T cell receptor (TCR alpha,beta) and the associated CD3 molecule on thymocytes from 10 DS and 27 control children. A significantly smaller proportion of cells expressing high levels of TCR alpha,beta was observed in DS thymuses compared to controls (17.0% vs. 34.3%, respectively; P less than 0.01). A similar observation was made for CD3, a molecule responsible for signal transduction through the TCR, where a lower proportion of cells expressing high levels of CD3 was found in DS compared to controls (18.4% vs. 43.3%, respectively; P less than 0.001). These data are evidence for aberrant T cell maturation in DS. In addition, our findings of decreased acquisition of high levels of the molecules which are critical for antigen-specific recognition by T cells suggest a possible mechanism for the decreased T cell function found in individuals with DS.
authors: Department of Pediatrics, University of California, San Francisco 94143.
authors: M
authors: M
authors: Murphy
authors: M J
authors: MJ
authors: Lempert
authors: L B
authors: LB
authors: Epstein
mesh_terms: D015703:Antigens, CD / Q000032:analysis*; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis*; D017252:CD3 Complex; D002648:Child; D004314:Down Syndrome / Q000276:immunology*; D005455:Fluorescent Antibody Technique; D006801:Humans; D011948:Receptors, Antigen, T-Cell / Q000032:analysis*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D011948:Receptors, Antigen, T-Cell