Expression of Antigens by Cultured Epithelial Cells: Comparison of Epidermis and Thymic Epithelium

Abstract

We have established long term in vitro cultures of human thymic epithelium and human epidermis free of contaminating fibroblasts. The cultured cells were examined using a panel of monoclonal antibodies which were raised against human thymic stroma and recognize tissue specific differentiation antigens of human epidermis and thymic epithelium. A subset of cultured epidermal cells (50%) and thymic epithelial cells (18%) expressed the TE-4 antigen characteristic of basal keratinocytes in skin and endocrine epithelium found in the subcapsular cortex and medulla of the thymus. Subpopulations of the cultured cells expressed the antigens detected by antibodies TE-8 and TE-15. In tissue sections antibodies TE-8 and TE-15 bound to the stratum granulosum and stratum corneum of skin and to the Hassall's bodies of thymus, and therefore recognize antigens characteristic of late stages of keratinized epithelial differentiation. In addition, a subset of thymic epithelial cells expressed the antigen detected by antibody TE-3 which is expressed by nonendocrine thymic epithelium found in the thymic cortex. Thus, in vitro cultures of both epidermal and thymic epithelial cells expressed the entire array of differentiation antigens detected by our panel of monoclonal antibodies. This approach can be used to evaluate the role of components of the thymic microenvironment at various stages of differentiation on developing T lymphocytes. In addition, the cultured epidermal cells can be used to evaluate epidermis as a site of extrathymic T cell maturation.

Corticosteroids Regulate Epithelial Cell Differentiation and Hassall Body Formation in the Human Thymus

“…TE cells were obtained by an explant technique using TE medium containing 67% DMEM (Life Technologies, Grand Island, NY), 22% Ham's F-12 (Life Technologies), 5% Fetal Clone II serum (HyClone, Logan, UT), 0.4 g/ml hydrocortisone, 5 g/ml insulin, 11 ng/ml recombinant human epidermal growth factor (Collaborative Biomedical, Bedford, MA), 0.18 M adenine, 10 Ϫ10 M cholera toxin (ICN Biomedicals, Aurora, OH), 0.25 g/ml Fungizone, and 50 g/ml gentamicin on mitomycin-C-treated NIH-3T3 fibroblast feeder layers as described (23,24). Contaminating fibroblasts were removed from TE cultures by treatment with 0.02% EDTA in PBS followed by complement-mediated lysis with mAb 1B10, which binds to a cell surface Ag on fibroblasts (25).…”

Antigenic Thymus-Epidermis Relationships

“…In thymus, the function of the epithelium with regard to maturation (or education) of T cells may be related to its stage of differentiation. The data recently reported by Singer et al [7] demonstrated antigenic similarities beetween two groups of structures: on the one hand, the thymic epithelial network and the epidermal basal cell layer and on the other hand, HC and the suprabasal epidermal cell layer. Our results (table IV) obtained with a new panel of antithymic epithelium MCA, confirm these similarities between the two groups of struc tures.…”

“…Antigenic similarities have been revealed us ing various human and experimental anti bodies [2][3][4][5][6][7]. Recently, the heterogeneity of the thymic epithelial cells was documented on the basis of keratin polypeptide analysis [29,30] or tissue-specific differentiation an tigens identified by MCA [31,32], These an tibodies were used to define antigenic similarities between thymic epithelial cells and kcratinocytes.…”

“…If was demonstrated by immunohistocheniistry that HC contained some keratin subunits found in the stratum corneum [4] and also a concanavalin-A-reactive glycoprotein (GP 37) expressed in the upper layers of the nor mal epidermis [6], Recently the use of MCA directed against keratin polypeptides [30] or components of the human thymic microen vironment [7] allowed us to confirm the similarities between HC and the terminally differentiated cells of the epidermis. Our results are in accordance with the recent data obtained in this field [7,30].…”

“…Only a few facts are actually known about the epidermis-thymus interactions which remain a matter of hypothesis in cutaneous immunopathology [1], Similari ties between skin and thymus have been postulated since antigenic cross-reactivities were demonstrated between thymic epitheli al cells and the epidermis [2][3][4][5][6][7], In addition to the expression of common antigens, func tional similarities between skin and thymus have been reported: (a) the production of thymopoietin (a thymic factor) by the cul tured epidermal cells [8], and (b) the capa bility of supernatants from keratinocytes to induce undifferentiated murine bone mar row cells and human T cells to express ter minal deoxynucleotidyl transferase, which is an early marker of T cell differentiation [9], Recently, Thy-l-positive dendritic cells have been described in mouse epidermis [10,11]. These cells are now considered as a source of extra-thymic population of T cell precursors [12].…”