Mouse fetal thymus lobes cultured in IL-2 generate CD3⁺, TCR-γδ-expressing CD4^-/CD8⁺ and CD4^-/CD8^- cells

Whole, undisrupted, 14-day fetal mouse thymus lobes were liquid-cultured in medium supplemented with 10 U/ml rIL-2. The cells that emerged from these fetal thymus lobes grew in an IL-2-dependent manner and showed non-MHC-restricted cytolytic activity. By two-color flow microfluorimetric analysis they could be subdivided into CD4^-/CD8⁺ and CD4^-/CD8^- subpopulations both of which contained CD3⁺ cells. Northern analysis of total cellular RNA revealed full-length transcripts of γ- and δ-message, predominantly the truncated (1.0 kb) β- and no detectable α-message. Taken together, these results show that by culturing 14-day fetal thymus lobes in IL-2, in the absence of deliberate mitogen stimulation, CD3⁺, TcR-γδ-expressing CD4^-/CD8⁺ and CD4^-/CD8^- T cells are obtained. Such cells may represent the precursors of similar cells found outside the thymus in adult mice.