In Vivo Biological Effect of Allogeneic Cultured Thymic Epithelium on Thymus‐Dependent Immunity in Athymic Nude Rats

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Abstract
We have extended our previous siudy of induction of T‐lymphocyte immunocompetence in athymic nude rats by cultured epithelium (CTE) of syngencic urigin to that by CTE of allogeneic origin. Immune responsiveness (IgG‐class antibody und delayed‐type hypersensi‐liviiy) after ovalbumin immunization is detectable by ‐1–6 weeks after transplantation. However, the antibody appears at a slower rate when compared with heterozygous immunocompeient littermates. Seven weeks after transplantation phytohaemagglutinm responsiveness of spleen cells is detectable, and in‘Independent areas of lymphoid organs lymphocytes with helper and non‐helper T‐cell phcnotype are presenl, bul at lower levels than those in heterozygous immunocompetenl littermates. Levels comparable to that of immunocompeient rals are reached about 20 weeks after transplantation. Since CTE contains thymocytes. control experiments consisted of transplantation with high numbers of allogeneic freshly isolated thymocytes in alhymic nude ratv These animals showed IgG‐class antibody formation after ovalbumin immunization, but at lower levels than CTE‐treated rats, and were almost negative in T‐cell immunocompetence assessed in the other assays. We conclude that CTE of allogeneic origin induces T‐eell immunocompetence in athymic nude rats to the level of heterozygous immunocompeteni littermates. This study adds to the rationale of CTE transplantation applied in treatment of thymic dysfunction.