Extracellular matrix of the human thymus: immunofluorescence studies on frozen sections and cultured epithelial cells.

Abstract

The immunohistochemical detection of elements of the human thymic extracellular matrix in situ and in vitro is described. In the normal thymus, the intracapsular and intraseptal fibers were strongly labeled by anti-type I collagen antiserum. Basement membranes bordering the capsule, septae, and perivascular spaces were intensely stained by anti-type IV collagen, anti-fibronectin, and anti-laminm sera. In hyperplastic myasthenia gravis thymuses, the major changes consisted of discontinuities of the basement membrane adjacent to clusters of epithelial (keratin-contaming) cells, among which an unusual connective framework (densely labeled by all the antisera) was observed. In vitro, most epithelial cells were strongly labeled by anti-fibronectin serum and to a lesser extent by the anti-type IV collagen and anti-laminin sera. In addition, fibronectin, laminin, and type IV collagen were detected in the intercellular spaces bordering the epithelial cells in culture. Results show that thymic epithelial cells participate in the synthesis of extracellular matrix elements, which as a result of their localization and influence on epithelial cell growth, should be regarded as constitutive components of the thymic microenvironment.

p38 MAPK is a critical regulator of the constitutive and the β4 integrin‐regulated expression of IL‐6 in human normal thymic epithelial cells

“…Previous and ours results have demonstrated that (1) TEC derived from normal thymus and grown to organized monolayers, constitutively produce extracellular matrix proteins (laminins, fibronectin and collagen type IV); (2) these cells display two sets of integrins polarized at discrete locations ( § 2 g 1 and § 3 g 1 heterodimers, mostly located at the TEC-TEC boundaries, and § 6 g 4, colocalized with its ligand laminin at the base of the monolayer); and (3) thymocyte or lymphocyte adhesion remodels this pattern, so that § 6 g 4 and § 3 g 1, but not § 2 g 1 integrins, cluster also around individual lymphoid cells, recognizing yet unknown cellular ligands expressed by T cells [10][11][12][13].…”

Triiodothyronine Modulates Thymocyte Migration

“…Both were polyclonal immunosera produced in rabbits by the injection of human plasma fibronectin or laminin purified from the murine Erlich sarcoma [29]. These reagents recognize their corresponding molecules in mouse and human thymuses [30,31]. Goat anti-rabbit IgG antibodies conjugated to fluoresceinisothiocyanate (FITC) were purchased from Pharmingen/Becton-Dickinson.…”

A monokine which binds to class II histocompatibility proteins

“…Thymic epithelial cells have also been shown to be the source of thymic hormones which induce the appearance of maturation markers on thymocytes (10). More recently, the epithelial cells have also been shown to be a source of IL-1 (11).…”