Cultured Thymic Epithelium. Its Morphological Characterization and Biological Effect in Vivo in Athymic Nude Rats

Abstract

The thymic epithelial cell plays an essential role in T cell maturation, either by direct contact with so-called “prethymic” precursor T cells, or by the secretion of biologically active factors (e.g. thymosin) (1). Apart from fetal thymus, transplantation of cultured thymic epithelium (CTE) has become a treatment procedure in patients with deficiency of thymic function, such as di George syndrome and some forms of severe combined immune deficiency. By culturing thymic expiants thymocytes disappear from the tissue (2), whose cells are responsible for graft-versus-host disease which may occur in the recipient. Conditions to get CTE with biological activity of the epithelial cells deprived of thymocytes are rather ill-defined. This prompted us to establish optimal culture conditions of CTE of human and rat origin for transplantation purposes. We looked for morphological criteria, and for the biological activity of CTE both in vitro (synthesis of biologically active factors) and in vivo (induction of thymus dependent immunity in athymic [nude] rats).