The development of a speech sound screening test for European French-speaking monolingual and bilingual children.

PURPOSE: This study presents normative data on a screening test, referred to as the Dépistage Rapide Articulation et Phonologie (DRAP), designed to detect European French-speaking children who are at risk for having speech sound disorders. METHOD: The test consists of 20 words which contain late-acquired phonological features such as medial and final /r/, consonant clusters, /s/C sequences, and alveolar and post-alveolar fricatives. The test was given to 196 children, monolingual and bilingual, living in Geneva and San Francisco, and ranging in age from 2.11 through to 6.11. Our analyses examined the influence of bilingualism, context (Geneva or San Francisco), gender and age on the test scores and also looked at the influence of these factors on phonological features in the test. RESULT: There were no strong effects of bilingualism, context, and gender on the test results but strong effects of age. Validity and internal consistency of the test were in the acceptable range. A focus on phonological features indicated that children had difficulty with final clusters and post-alveolar fricatives. CONCLUSION: The study provides encouraging results for the use of this test as a screening measure with French-speaking children.

Visualizing intermolecular interactions in T cells.

The use of appropriate fluorescent proteins has allowed the use of FRET microscopy for investigation of intermolecular interactions in living cells. This method has the advantage of both being dynamic and of working at the subcellular level, so that the time and place where proteins interact can be visualized. We have used FRET microscopy to analyze the interactions between the T cell antigen receptor and the coreceptors CD4 and CD8. This chapter reviews data on how these coreceptors are recruited to the immunological synapse, and how they interact when the T cell is stimulated by different ligands.

Thymocyte stimulation by anti-TCR-beta, but not by anti-TCR-alpha, leads to induction of developmental transcription program.

Anti-T cell receptor (aTCR) antibody (Ab) stimulation of T cells results in TCR down-modulation and T cell activation. Differences in the effect of anti-alpha-chain and beta-chain Ab have been reported on thymocytes. Anti-beta-chain Ab but not anti-alpha-chain reagents cause long-term TCR down-modulation. However, both types of Ab result in TCR cross-linking and activate early steps in signal transduction. In this study, we show that TCR internalization and calcium flux, hallmarks of T cell activation, are similar with aValpha and aVbeta treatment. Therefore, we have compared the gene expression profiles of preselection thymocytes stimulated with these reagents. We find that aValpha treatment does not cause any significant change in gene expression compared with control culture conditions. In contrast, aVbeta stimulation results in numerous changes in gene expression. The alterations of expression of genes known to be expressed in thymocytes are similar to changes caused by positive thymic selection, suggesting that the expression of some of the genes without known roles in thymocyte development and of novel genes whose expression is found to be altered may also be involved in this process.

Thymocyte stimulation by anti-TCR-ß, but not by anti-TCR-α, leads to induction of developmental transcription program.

Anti-T cell receptor (aTCR) antibody (Ab) stimulation of T cells results in TCR down-modulation and T cell activation. Differences in the effect of anti-α-chain and ß-chain Ab have been reported on thymocytes. Anti-ß-chain Ab but not anti-α-chain reagents cause long-term TCR down-modulation. However, both types of Ab result in TCR cross-linking and activate early steps in signal transduction. In this study, we show that TCR iternalization and calcium flux, hallmarks of T cell activation, are similar with aVα and aVß treatment. Therefore, we have compared the gene expression profiles of preselection thymocytes stimulated with these reagents. We find that aVα treatment does not cause any significant change in gene expression compared with control culture conditions. In contrast, aVß stimulation results in numerous changes in gene expression. The alterations of expression of genes known to be expressed in thymocytes are similar to changes caused by positive thymic selection, suggesting that the expression of some of the genes without known roles in thymocyte development and of novel genes whose expression is found to be altered may also be involved in this process.

Surprisingly minor influence of TRAV11 (Valpha14) polymorphism on NK T-receptor mCD1/alpha-galactosylceramide binding kinetics.

Defects in natural killer T (NK T) cell function and of interleukin-4 -production in SJL and NOD mice have been linked to susceptibility to autoimmune disease. As SJL and NOD mice both carry the T-cell receptor (TCR) alpha-chain locus "c" (Tcra(c)) haplotype, found in few other strains, we have attempted to determine the influence of Tcra polymorphism on NK T-cell recognition of ligand, selection, and immune responses. The majority of NK T cells use an "invariant" TRAV11J15 (previously called AV14J18 or Valpha14 Jalpha281) alpha- chain paired with either TRBV13-2, BV29, or BV1 to recognize ligands presented by mCD1 molecules, including the glycolipid alpha-galactosylceramide (alpha-GalCer). Sequencing of TRAV11 from the mouse strains B10.A (encoding the Tcra(b) haplotype), B10.A- Tcra(c), and NOD (Tcra(c)) shows that Tcra(c) has a single TRAV11 gene (TRAV11*01) and that Tcra(b) has a single expressed gene (TRAV11*02), plus a closely related pseudogene. There is no apparent difference in alpha-chain J-region usage or in the CDR3alpha sequence at the TRAV11-J15 junction between the haplotypes in TRAV11-bearing NK T cells. Using Biacore and tetramer-binding and decay assays, we have determined that the interaction between Tcra(c) TRAV11*01 NK T TCR and the mCD1/alpha-GalCer complex is slightly weaker than that of Tcra(b) (i.e., TRAV11*02) NK T TCR. These differences are minor compared with differences between agonist and antagonist ligands in other TCR systems, suggesting that it is unlikely that TCR polymorphism explains the defect in NK T cells in the autoimmune mouse strains.

Allelic exclusion of the TCR alpha-chain is an active process requiring TCR-mediated signaling and c-Cbl.

Phenotypic allelic exclusion at the TCRalpha locus is developmentally regulated in thymocytes. Many immature thymocytes express two cell surface alpha-chain species. Following positive selection, the vast majority of mature thymocytes and peripheral T cells display a single cell surface alpha-chain. A posttranslational mechanism occurring at the same time as positive selection and TCR up-regulation leads to this phenotypic allelic exclusion. Different models have been proposed to explain the posttranslational regulation of the alpha-chain allelic exclusion. In this study, we report that allelic exclusion is not regulated by competition between distinct alpha-chains for a single beta-chain, as proposed by the dueling alpha-chain model, nor by limiting CD3 zeta-chain in mature TCR(high) thymocytes. Our data instead favor the selective retention model where the positive selection signal through the TCR leads to phenotypic allelic exclusion by specifically maintaining cell surface expression of the selected alpha-chain while the nonselected alpha-chain is internalized. The use of inhibitors specific for Lck and/or other Src kinases indicates a role for these protein tyrosine kinases in the signaling events leading to the down-regulation of the nonselectable alpha-chain. Loss of the ubiquitin ligase/TCR signaling adapter molecule c-Cbl, which is important in TCR down-modulation and is a negative regulator of T cell signaling, leads to increased dual alpha-chain expression on the cell surface of double-positive thymocytes. Thus, not only is there an important role for TCR signaling in causing alpha-chain allelic exclusion, but differential ubiquitination by c-Cbl may be an important factor in causing only the nonselected alpha-chain to be down-modulated.