TCR-DEPENDENT AND TCR-INDEPENDENT SIGNALING MECHANISMS DIFFERENTIALLYREGULATE LYMPHOKINE GENE-EXPRESSION IN THE MURINE T-HELPER CLONE D10.G4.1

The signaling mechanisms that regulate lymphokine gene expression in t he murine Th2 clone D10.G4.1 were investigated by comparing the steady state mRNA levels of six lymphokine genes in response to cellular tre atment with various activators and inhibitors of several key signaling pathways. A surprising degree of differential regulation was found. A ll of the genes studied (IL-3, IL-4, IL-5, IL-6, IL-10, and granulocyt e-macrophage (GM)-CSF) were induced by the lectin Con A and the-TCR id iotype-specific mAb 3D3. However, the induction of the IL-3, IL-4, and GM-CSF genes, but not the IL-5, IL-6, and IL-10 genes, was strongly i nhibited by cyclosporin A. Furthermore, IL-5, IL-6, and IL-10 genes we re independently induced by IL-1 alpha, the phorbol ester PMA, and by forskolin, an activator of adenylate cyclase. Results of studies perfo rmed with use of the Ca2+ ionophore A23187 indicated that elevation of intracellular Ca2+ levels is sufficient to fully induce IL-3 and IL-4 gene expression. Protein kinase C activation was also required for fu ll induction of the GM-CSF gene and seemed to be obligatory for maxima l IL-5 gene expression. The patterns of mRNA induction by the differen t stimuli broadly correlated with increased rates of transcription. In addition to their induction by IL-1 alpha, the IL-5, IL-6, and IL-10 genes were also induced by mAbs to CD2 and to CD45. In contrast, addin g CD45 mAb strongly inhibited the induction of IL-3, IL-4, and CM-CSF genes through TCR stimulation. These results indicate that distinct gr oups of lymphokine genes may be differentially regulated by signaling pathways that are activated by stimulation of the TCR and other cell s urface molecules.