title: Characterization of CD34+ thymic stromal cells located in the subcapsular cortex of the human thymus.
abstract: In this paper we report that suspensions of human fetal thymocytes contain cells that express high levels of CD34 and Thy-1. These cells were characterized with regard to location within the thymus, phenotype, and function. Confocal laser scan analysis of frozen sections of fetal thymus with anti-CD34 and Thy-1 antibodies revealed that the double-labeled cells were located in the pericortical area. In addition, it was found that the CD34+Thy-1+ cells lacked CD45 and CD50, indicating that these cells are not of hematopoietic origin; this was confirmed by the finding that these cells could be cultured as adherent cells in a medium with cholera toxin and dexamethasone, but failed to grow in mixtures of hematopoietic growth factors. Further analysis indicated that most cultured CD34+Thy-1+ cells expressed cytokeratin (CK) 14 but lacked CK 13, suggesting that these cells are immature epithelial cells. Cultured CD34+Thy-1+ cells were able to induce differentiation of CD1-CD34+CD3-CD4-CD8- thymic precursors into CD4+CD8+ cells in a reaggregate culture in the absence of exogenous cytokines. The CD4+CD8+ cells that developed in these cultures did not express CD3, indicating that CD34+Thy-1+ thymic stromal cells are not capable of completing full T cell differentiation of thymic hematopoietic progenitor cells.
authors.affiliation: Division of Immunology, The Netherlands Cancer Institute, Amsterdam.
authors.forename: E
authors.initials: E
authors.lastname: Martínez-Cáceres
authors.forename: A C
authors.initials: AC
authors.lastname: Jaleco
authors.forename: P
authors.initials: P
authors.lastname: Res
authors.forename: E
authors.initials: E
authors.lastname: Noteboom
authors.forename: K
authors.initials: K
authors.lastname: Weijer
authors.forename: H
authors.initials: H
authors.lastname: Spits
mesh_terms: D002454:Cell Differentiation / Q000276:immunology; D002478:Cells, Cultured; D006801:Humans; D018613:Microscopy, Confocal; D009924:Organ Culture Techniques; D017154:Stromal Cells / Q000276:immunology; D018800:Thy-1 Antigens / Q000032:analysis*; D013950:Thymus Gland / Q000166:cytology / Q000196:embryology / Q000276:immunology*
chemical_list: D018800:Thy-1 Antigens