title: Exogenous control of I-A expression in fetal thymus explants.
abstract: With the use of a system in which 14 day fetal thymus lobes were cultured in vitro with bone marrow or other lymphoid cells, evidence was obtained that entry of macrophage/dendritic cells (M phi/DC) into the thymus causes a marked rise in the density of endogenous I-A molecules expressed in the cortex, presumably on epithelial cells. High cortical I-A expression also occurred when thymus lobes were cultured with supernatants containing IFN-gamma; addition of anti-IFN-gamma antibody blocked I-A induction. The working hypothesis for these findings is that cellular interactions occurring in the medullary region between M phi/DC and a subset of thymocytes leads to production of IFN-gamma, which then diffuses into the cortex and promotes epithelial I-A expression. The possible relevance of this scheme to the process of thymic "education" is discussed.
authors.forename: D
authors.initials: D
authors.lastname: Lo
authors.forename: J
authors.initials: J
authors.lastname: Sprent
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells; D002465:Cell Movement; D046508:Culture Techniques; D006412:Hematopoietic Stem Cells / Q000276:immunology; D000949:Histocompatibility Antigens Class II / Q000276:immunology*; D008099:Liver / Q000166:cytology; D051379:Mice; D013950:Thymus Gland / Q000196:embryology / Q000276:immunology*
chemical_list: D000949:Histocompatibility Antigens Class II