Control of lymphokine expression in T helper 2 cells.

In this report we present evidence that Con A-activated T helper 2 cells transcribe the interleukin 2 (IL-2) gene when cycloheximide is added 3 hr after stimulation. This IL-2 mRNA can be translated into functional protein. However, no steady-state mRNA for gamma-interferon can be detected under the same experimental conditions. Furthermore, when cycloheximide is administered at time 0 of activation, no IL-2 mRNA is seen. Nuclear run-on experiments indicate that IL-2 transcription in T helper 2 cells depends on the presence of cycloheximide. It is likely, therefore, that activation of T helper 2 cells leads to the production of a labile regulatory protein that represses the expression of the IL-2 gene. These findings provide insight into the molecular mechanism that governs the differentiation of interleukin 4-producing T helper 2 cells from IL-2-producing precursor cells.