Selective elimination of double‐positive immature thymocytes by a thymic epithelial cell line

A cloned epithelial cell line, TEL‐2, has been established from the stroma tissues of normal mouse thymus. Incubation of mouse thymocytes on TEL‐2 cells resulted in the selective elimination of double‐positive (CD4⁺CD8⁺ cells from the culture, whereas single‐positive (CD4⁺ CD8⁻ or CD4⁻CD8) thymocytes remaining in the culture were concentrated in non‐integrated cell population. The CD3⁻ or CD3 low‐positive thymocytes were also eliminated by the TEL‐2 cells from the culture, followed by the concentration of CD3 high‐positive cells in the culture. Only intact viable thymocytes were integrated into TEL‐2 cells. Electron microscopic examination showed that the integrated cells into TEL‐2 cytoplasm were gradually degenerated. Mature single‐positive T cells, mature B cells or double‐negative thymocytes were not integrated into TEL‐2 cells. The TEL‐2 cell may provide information on the mechanism of selective disappearance of double‐positive immature cells from the thymus.