title: Bone marrow-derived cells fail to induce positive selection in thymus reaggregation cultures.
abstract: The requirements for inducing positive selection of T cells were examined in thymus reaggregation cultures, a system in which dispersed populations of immature CD4+8+ cells and purified thymic epithelial cells (TEC) are reaggregated in tissue culture. Studies with TEC from mice selectively lacking major histocompatibility complex (MHC) class I (I-II+), class II (I+II-), or both class I and II (I-II-) molecules showed that class II expression was essential for the differentiation of CD4+8+ cells into CD4+8- cells. Unexpectedly, the generation of TCRhi CD4-8+ cells from CD4+8+ cells was apparent with I-II+ TEC but not with I-II- TEC, perhaps reflecting cross-reactive specificity of CD4-8+ cells for class II molecules. Significantly, the failure of I-II- TEC to generate TCRhi CD4+8- or CD4-8+ cells could not be overcome by adding MHC+ bone marrow-derived cells. These findings, together with experiments on purified subsets of TEC, suggest that positive selection in thymus reaggregation cultures is an exclusive property of cortical TEC.
authors.affiliation: Department of Immunology, IMM4, The Scripps Research Institute, La Jolla, California 92037, USA.
authors.forename: B B
authors.initials: BB
authors.lastname: Ernst
authors.forename: C D
authors.initials: CD
authors.lastname: Surh
authors.forename: J
authors.initials: J
authors.lastname: Sprent
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis; D001853:Bone Marrow / Q000276:immunology; D001854:Bone Marrow Cells; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology; D002449:Cell Aggregation; D002454:Cell Differentiation; D002478:Cells, Cultured; D004847:Epithelial Cells; D005333:Fetus; D005434:Flow Cytometry; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000276:immunology; D015395:Histocompatibility Antigens Class I / Q000032:analysis / Q000276:immunology; D000949:Histocompatibility Antigens Class II / Q000032:analysis / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D008817:Mice, Mutant Strains; D011948:Receptors, Antigen, T-Cell / Q000276:immunology; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology*; D013601:T-Lymphocytes / Q000166:cytology* / Q000276:immunology*; D013950:Thymus Gland / Q000166:cytology / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte; D015395:Histocompatibility Antigens Class I; D000949:Histocompatibility Antigens Class II; D011948:Receptors, Antigen, T-Cell