Interleukin 1‐induced maturation of progenitor thymocytes

Regulation of thymocyte development was assesed by culturing purified CD4−CD8− thymocytes with cytokines. Sorted CD3−CD4−CD8− adult thymocytes responded to the combination of interleukin (IL) 1 plus IL 2 without additional mitogens or co-mitogens with both cellular proliferation and cell surface expression of the T cell receptor (TcR)/CD3 complex. IL 2 alone induced neither proliferation nor cell surface TcR/CD3 expression. IL 1 alone was sufficient to induce cell surface TcR/CD3 without proliferation. Prior to stimulation with cytokines, the progenitor CD4−CD8− thymocytes accumulated TcR β and CD3 γ, δ, e and ϱ, mRNA but TcR α mRNA was not detectable. Stimulation with IL 1 led to a dramatic induction of TcR α mRNA without an increase in the other transcripts. These studies suggest that IL 1 regulates the differentiation status of immature adult thymocytes. Nuclear run-on studies suggested that the increase in TcR α mRNA accumulation induced by cytokines might result from post-transcriptional accumulation.