Interleukin 7 preferentially supports the growth of γδ T cell receptor-bearing T cells from fetal thymocytes in vitro

Abstract

Murine fetal thymus cells were cultured with various interleukins (IL-1, 2, 3, 4, 5, 6, and 7) in the absence or presence of phorbol 12-myristate 13-acetate (PMA), and it was found that only IL-4 and IL-7 induced a prominent proliferative response In the presence of PMA. A large proportion of cells grown in the cultures of fetal thymus cells (days 15 and 17 of gestation) stimulated with PMA plus IL-4 or with PMA plus IL-2 remained CD4-CD8-. In marked contrast, nearly 70% of the cells generated in the cultures of the same fetal thymocytes stimulated with PMA plus IL-7 expressed CD8 on their surface. Approximately 30% of these cells expressed TCR γ whereas TCR αβ⁺ cells were virtually undetectable. The cells grown in cultures stimulated with PMA plus IL-7 comprised three populations: CD4-Lyt-2–3-, CD4-Lyt-2⁺Lyt-3^- and CD4-Lyt-2⁺Lyt-3⁺, and that TCR γ⁺ T cells were found in all three populations. it was also found that the addition of IL-7 in the culture of adult CD4-CD8- thymocytes on the monolayer of a thymic stromal cell line, which selectively promotes the generation of αβ T cells, resulted in the generation of γ T cells. These results strongly suggest that IL-7 plays an important role in the development of γ cells.