title: Allelic exclusion of mouse T cell receptor alpha chains occurs at the time of thymocyte TCR up-regulation.
abstract: We report a detailed analysis of TCR V alpha and V beta chain expression on immature versus mature thymocytes of normal, TCR beta-transgenic, and TCR alpha-hemizygous mice. Chain pairing between TCR V alpha and V beta chains is random on immature thymocytes, but individual chain pairs are selected in mature thymocytes. This indicates that V alpha-V beta chain pairing preferences are determined during thymic selection, and not as a result of structural constraints. Dual V alpha chain expression is found frequently on immature, but not mature thymocytes. It is not found in TCR alpha-hemizygous mice, showing that cell surface expression of dual alpha chains is caused by lack of allelic exclusion in immature thymocytes. Down-regulation of one of the alpha chains occurs concurrently with differentiation from TCRlo, CD69- to TCRhi, CD69+ phenotype, suggesting that it is associated with positive selection of the functional TCR.
authors.affiliation: Department of Immunology, Scripps Research Institute, La Jolla, California 92037, USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Alam
authors.forename: I N
authors.initials: IN
authors.lastname: Crispe
authors.forename: N R
authors.initials: NR
authors.lastname: Gascoigne
mesh_terms: D000483:Alleles; D000818:Animals; D015703:Antigens, CD / Q000276:immunology; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*; D013950:Thymus Gland / Q000276:immunology*; D015854:Up-Regulation
chemical_list: D015703:Antigens, CD; D016693:Receptors, Antigen, T-Cell, alpha-beta