title: Complete TCR-delta rearrangements and partial (D-J) recombination of the TCR-beta locus in CD34+7+ precursors from human cord blood.
abstract: In the neonatal human thymus, early immature precursors co-express CD34 and CD7 cell surface Ags, and we have recently shown that its most primitive CD34+7+1- fraction includes TCR-beta-rearranging cells. Bone marrow and cord blood also contain a CD34+7+ population. Although this population is heterogeneous in terms of both phenotype and differentiation capacities, it may include T cell-committed thymus colonizing precursors (prothymocytes). Recently, it has been shown in the mouse that initiation of TCR-beta rearrangements is not restricted to early thymocytes. In the present study, we examined the TCR-beta and TCR-delta rearrangement and transcription status of cord blood CD34+7- and CD34+7+ subpopulations. RNA and DNA were isolated from these cell subsets purified by two consecutive rounds of fluorescence-activated cell sorting from CD3-depleted cord blood cells. Using D-J(beta) or V-J(beta) primer sets and genomic DNA PCR amplification, we showed that CD34+7+, but not CD34+7-, contained D-J(beta) rearrangements without concomitant V-D(beta) recombination. These partial TCR-beta rearrangements within CD34+7+ progenitors were also confirmed at the transcriptional level. Furthermore, whereas none of the CD34+ cord blood cell fraction expressed TCR-alpha transcripts, mature V(delta)1-C(delta) mRNA could be amplified from the CD34+7+ subset. The TdT gene was also transcriptionally active in CD34+7+ cells, thus confirming their lymphoid progenitor content. These data indicate that cord blood CD34+7+ cells, like CD34+7+1- neonatal thymocytes, can initiate TCR-beta gene recombination, reinforcing the idea that T cell commitment may occur before prothymocyte migration to the thymus.
authors.affiliation: Laboratory of Cellular and Tissue Immunology, National Center for Scientific Research (CNRS), Paris, France.
authors.forename: S
authors.initials: S
authors.lastname: Ktorza
authors.forename: C
authors.initials: C
authors.lastname: Blanc
authors.forename: C
authors.initials: C
authors.lastname: Laurent
authors.forename: S
authors.initials: S
authors.lastname: Sarun
authors.forename: M P
authors.initials: MP
authors.lastname: Verpilleux
authors.forename: P
authors.initials: P
authors.lastname: Debré
authors.forename: C
authors.initials: C
authors.lastname: Schmitt
mesh_terms: D000818:Animals; D018952:Antigens, CD34 / Q000378:metabolism; D019011:Antigens, CD7 / Q000378:metabolism; D001483:Base Sequence; D002454:Cell Differentiation; D017931:DNA Primers / Q000235:genetics; D015342:DNA Probes / Q000235:genetics; D005312:Fetal Blood / Q000166:cytology / Q000276:immunology*; D015333:Gene Rearrangement, beta-Chain T-Cell Antigen Receptor; D016694:Gene Rearrangement, delta-Chain T-Cell Antigen Receptor; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000276:immunology*; D006801:Humans; D018189:Immunomagnetic Separation; D007231:Infant, Newborn; D051379:Mice; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics*; D011995:Recombination, Genetic; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology*; D014158:Transcription, Genetic
chemical_list: D018952:Antigens, CD34; D019011:Antigens, CD7; D017931:DNA Primers; D015342:DNA Probes; D016693:Receptors, Antigen, T-Cell, alpha-beta