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.
Phenotypic characterization and ontogeny of mesodermal-derived and endocrine epithelial components of the human thymic microenvironment.
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B F Haynes, R M Scearce, D F Lobach, L L Hensley; Phenotypic characterization and ontogeny of mesodermal-derived and endocrine epithelial components of the human thymic microenvironment.. J Exp Med 1 April 1984; 159 (4): 1149–1168. doi: https://doi.org/10.1084/jem.159.4.1149
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