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T-cell receptor beta-chain gene rearrangement and expression during human thymic ontogenesis.

Abstract：

:T-cell receptor (TCR) beta-chain proteins appear early (approximately 15th week of gestation) during human thymic ontogenesis. These beta-chain proteins, which appear before terminal deoxynucleotidyl transferase (TdT), could be an expression of a fully rearranged (V-D-J), incompletely rearranged (D-J), or germline TCR beta-chain gene. The aims of this study, performed from the 15th week onward, were the following: (1) to investigate whether or not TCR beta gene rearranges at an early stage during human thymic ontogenesis; (2) to investigate whether complete presumptive functional (1.3 kb) TCR beta gene transcript is present at these early stages of development, or if incomplete (1 kb) or germ-line (1.1 kb) transcripts are expressed; (3) to examine the phenotype of TCR beta-chain+ cells with two-color fluorescence using monoclonal antibody (MoAb) beta F1 and MoAbs that recognize CD1, CD2, CD3, CD4, CD8, CD5, and CD7 antigens (rabbit anti-calf TdT antiserum was used to detect TdT); and (4) to demonstrate whether or not beta gene N-diversity regions are detectable as early as the 15th week and whether or not N-nucleotide insertions correlate to TdT expression. Fifteen- to 22-week fetal thymuses and pediatric thymuses were investigated. We demonstrated that TCR beta-chain gene rearranged as early as the 15th week in human thymus and that a complete functional TCR beta gene transcript was expressed at these early stages of human development. No other analyses to date have investigated TCR beta gene expression in early human thymus using molecular biology techniques. No significant differences were detectable between phenotypic analysis of fetal and pediatric samples, except for TdT expression, which appeared after the 20th week. Essentially all mCD3+ (OKT3+) cells were beta-chain+ at the different weeks investigated. A significant percentage of CD1+ cells were beta-chain+, and the percentage increased along with the age of development. After the 20th week, we identified three main populations: TdT+, cCD3+, beta F-(early thymic precursors); TdT+, CD1+, beta F1+ (intermediate maturity cortical thymocytes); and TdT-, mCD3+, beta F1++ (mature medullary thymocytes). Given these values, we may consider beta-chain expression an ordered process. beta gene N-nucleotide insertions were correlated to TdT expression, since N-regions increased considerably after the 20th week. A further increase of N-nucleotide insertions was detected from the 22nd week to the 32nd week.

journal_name

Blood

journal_title

Blood

authors

Bonati A,Zanelli P,Ferrari S,Plebani A,Starcich B,Savi M,Neri TM

subject

Has Abstract

pub_date

1992-03-15 00:00:00

pages

1472-83

issue

eissn

0006-4971

issn

1528-0020

journal_volume

pub_type

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T-cell receptor beta-chain gene rearrangement and expression during human thymic ontogenesis.