title: Phenotypic characterization and ontogeny of mesodermal-derived and endocrine epithelial components of the human thymic microenvironment.
abstract: Using murine monoclonal antibodies TE-4 and TE-7 raised against human thymic stroma, we identified two distinct and mutually exclusive thymic microenvironment components: the thymic endocrine epithelium (TE-4+) and mesodermal-derived fibrous stroma (TE-7+). TE-4-reactive epithelium did not react with antibody TE-7, contained thymosin alpha 1 and keratin, and expressed other known markers of thymic endocrine epithelium (A2B5 and p19). Moreover, TE-4+ thymic epithelial cells strongly expressed class I (HLA-A, -B and -C) and class II (Ia-like) major histocompatibility complex (MHC) antigens. In contrast, TE-7+ thymic fibrous stroma did not react with antibody TE-4, did not contain thymosin alpha 1 nor keratin, and did not express the thymic endocrine epithelium markers A2B5 and p19. TE-7+ thymic stromal cells weakly expressed class I and did not express class II MHC antigens. Both TE-4+ and TE-7+ thymic microenvironment compartments were identifiable in thymus from 7 wk gestation through adult life. At 7 wk fetal gestation, TE-7+ stroma surrounded a cylindrical TE-4+, A2B5+ thymic epithelial rudiment. Between 10 and 15 wk fetal gestation, TE-7+ thymic stroma surrounded early thymic lobules. By 15 wk fetal gestation, antibody TE-4 defined subcapsular cortical and medullary zones of endocrine thymic epithelium, while antibody TE-7 bound to interlobular fibrous septae, vessels, and thymic fibrous capsule. While otherwise specific for endocrine thymic epithelium, antibody TE-4 reacted with the basal layer of squamous epithelium in skin, tonsil, conjunctiva, and upper esophagus.
mesh_terms: D000293:Adolescent; D000328:Adult; D000375:Aging; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000937:Antigen-Antibody Reactions; D000951:Antigens, Neoplasm / Q000235:genetics / Q000276:immunology; D000954:Antigens, Surface / Q000235:genetics / Q000276:immunology; D002450:Cell Communication; D002648:Child; D002675:Child, Preschool; D004702:Endocrine Glands / Q000166:cytology / Q000276:immunology* / Q000502:physiology; D004847:Epithelial Cells; D004848:Epithelium / Q000276:immunology / Q000502:physiology; D000939:Epitopes / Q000235:genetics; D005260:Female; D006801:Humans; D007223:Infant; D007633:Keratins / Q000276:immunology; D008562:Membrane Glycoproteins; D008648:Mesoderm / Q000166:cytology / Q000276:immunology* / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D009928:Organ Specificity; D010641:Phenotype; D011247:Pregnancy; D000077596:Thymalfasin; D013947:Thymosin / Q000031:analogs & derivatives / Q000276:immunology; D013950:Thymus Gland / Q000196:embryology / Q000276:immunology* / Q000502:physiology
chemical_list: D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; D000954:Antigens, Surface; D000939:Epitopes; D008562:Membrane Glycoproteins; C028388:thymus-leukemia antigens; D013947:Thymosin; D007633:Keratins; D000077596:Thymalfasin