Responsiveness of Fetal and Adult CD4-, CD8- Thymocytes to T Cell Activation

摘要

Day-14 fetal CD4-, CD8- thymocytes showed a greater proliferative response to PMA + IL-4 than did adult double-negative thymocytes. In contrast, adult double-negative thymocytes were more responsive to PMA + IL-1 + IL-2 or to IL-1 + IL-2 alone. The adult double-negative thymocytes showed significantly greater proliferation than fetal thymocytes after stimulation via anti-CD 3 or anti-Thy-1 in the presence or absence of interleukins (IL-1 + IL-2 or IL-4). Adult CD4-, CD8- thymocytes also exhibited greater calcium mobilization following anti-CD3 stimulation IL-2-dependent activation with anti-Thy-1 or IL-2 in the absence of PMA resulted in marked expansion of CD 3+, F23.1+, CD4-, CD8-thymocytes, a population absent in fetal thymocytes but constituting 4% of pre-cultured CD4-, CD8-adult thymocytes. IL-4 + PMA failed to expand this CD3+ population. It is hypothesized that before expression of functional TCR, T cell development may be more dependent on activation pathways not using IL-2; after TCR expression, IL-2 dependent pathways, including Thy-1-mediated stimulation, become functional. Keywords: T cell ontogeny; Thymus; T cell receptor; Calcium; Interleukin; Lymphocyte activation; Reprints. (AW)