Elizabeth A. Harden

In vitro growth and phenotypic characterization of mesodermal-derived and epithelial components of normal and abnormal human thymus

Long-term in vitro cultures of human thymic tissue were established and phenotypically characterized using monoclonal reagents that define distinct components of the human thymic microenvironment. The epithelial component of the thymus, defined by monoclonal antibodies TE-3, TE-4, BBTECS, and AE1 (anti-keratin) was isolated from the mesodermal component, defined by antibody TE-7, and maintained separately in long-term culture. The epithelial cells were subcultured repeatedly and recovered from storage in liquid nitrogen. The in vitro phenotype of the cultured cells was compared to that of cultured human epidermal cells. A subpopulation of cultured thymic epithelial cells along with a subpopulation of cultured epidermal cells expressed antigens (TE-8, TE-15) characteristic of late stages of keratinized epithelial cell differentiation. Thus, we have established a system whereby components of the human thymic microenvironment can be cultivated in vitro while maintaining the capacity to differentiate. 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, keratin-containing thymic epithelial cells were successfully cultured from thymuses obtained from patients with myasthenia gravis and thymoma. Cultivation of abnormal thymic epithelium will provide insight into aberrant T lymphocyte-thymic epithelial interaction.

Antibody 3–40 Binds to Keratin and Vimentin Intermediate Filaments

In 1983, Naito et al. reported the production of the murine monoclonal antibody 3–40, produced by immunizing mice with the human T-ALL cell line MOLT-4 (1). By cytotoxicity, absorption, and indirect immunofluorescence assays, antibody 3–40 reacted with a 35–40-Kd surface protein on most T-ALL cell lines, but not with surface molecules of normal hematopoietic cells, including thymocytes (1).