title: Fibroblast dependency during early thymocyte development maps to the CD25+ CD44+ stage and involves interactions with fibroblast matrix molecules.
abstract: We have investigated the role of specific components of the thymic stroma during development of CD4-8-T cell precursors by separating and reaggregating precursor subsets with individual or combinations of stromal cells. We show that while the development of CD25+ 44+ precursors is dependent upon a combination of major histocompatibility complex (MHC) class II+ thymic epithelial cells and fibroblasts, their direct descendants, CD25+ 44- precursors, develop to the CD4+ 8+ stage in the presence of MHC class II+ thymic epithelial cells alone. Thus, CD25+ 44+ precursors are the last developmental stage to be dependent upon fibroblast support. In addition, while metabolically inactive, 1-ethyl-3-(3'-dimethylaminopropyl) carbodiimide (ECDI)-treated fibroblasts retain the ability to promote T cell development, prior treatment with hyaluronidase abrogates this effect, suggesting that fibroblast-associated extracellular matrix components are the key elements involved. In support of this, we show that fibroblasts are located in cortical regions of the thymus where T cell precursors are known to reside, and that these fibroblasts are associated with an extensive extracellular matrix not found on thymic epithelial cells. Finally, antibodies to alpha 4 integrin and CD44 interfere with the efficiency with which CD4+ 8+ cells are generated from CD25+ 44+ precursors in reaggregate cultures and also reduce the binding of the latter to 3T3 fibroblasts, suggesting these molecules play a role in bringing T cell precursors into contact with fibroblast-associated extracellular matrix.
authors.affiliation: Department of Anatomy/Centre for Clinical Research in Immunology and Signalling, Medical School, University of Birmingham, GB. andersog@novell2.bham.ac.uk
authors.forename: G
authors.initials: G
authors.lastname: Anderson
authors.forename: K L
authors.initials: KL
authors.lastname: Anderson
authors.forename: E Z
authors.initials: EZ
authors.lastname: Tchilian
authors.forename: J J
authors.initials: JJ
authors.lastname: Owen
authors.forename: E J
authors.initials: EJ
authors.lastname: Jenkinson
mesh_terms: D016475:3T3 Cells; D000818:Animals; D000831:Animals, Newborn; D000911:Antibodies, Monoclonal / Q000276:immunology; D015703:Antigens, CD / Q000276:immunology; D015704:CD4 Antigens / Q000032:analysis; D016827:CD8 Antigens / Q000032:analysis; D002449:Cell Aggregation / Q000276:immunology; D002450:Cell Communication / Q000276:immunology*; D002454:Cell Differentiation / Q000276:immunology; D005022:Ethyldimethylaminopropyl Carbodiimide; D016326:Extracellular Matrix Proteins / Q000096:biosynthesis / Q000378:metabolism*; D005347:Fibroblasts / Q000276:immunology; D006412:Hematopoietic Stem Cells / Q000276:immunology; D018960:Hyaluronan Receptors / Q000032:analysis* / Q000276:immunology; D006821:Hyaluronoglucosaminidase; D039441:Integrin alpha4; D051379:Mice; D008807:Mice, Inbred BALB C; D011817:Rabbits; D015375:Receptors, Interleukin-2 / Q000032:analysis*; D017154:Stromal Cells / Q000276:immunology; D016176:T-Lymphocyte Subsets / Q000166:cytology* / Q000276:immunology; D013950:Thymus Gland / Q000166:cytology* / Q000196:embryology / Q000254:growth & development
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D015704:CD4 Antigens; D016827:CD8 Antigens; D016326:Extracellular Matrix Proteins; D018960:Hyaluronan Receptors; D015375:Receptors, Interleukin-2; D039441:Integrin alpha4; D006821:Hyaluronoglucosaminidase; D005022:Ethyldimethylaminopropyl Carbodiimide