INDUCTION OF THE TNF-ALPHA PROMOTER IN THE MURINE DENDRITIC CELL-LINE-18 AND THE MURINE MAST-CELL LINE CPII IS DIFFERENTLY REGULATED

While it was recently shown that activation of dendritic cells (DC) re sults in the production of a number of cytokines, the signal pathways and transcription factors involved in this process have not been descr ibed. To address this issue we compared the events resulting in the ac tivation of the human TNF-alpha promoter occurring in the fetal dendri tic cell line 18 (DC18) with those in the well-characterized murine ma st cell line CPII. As stimuli we employed the protein kinase C inducer , PMA, and the Ca2+ ionophore, ionomycin, both of which are known to a ctivate a large variety of intracellular signaling pathways. In the DC 18 cells, PMA alone induces the TNF-alpha promoter in a macrolide-inse nsitive manner. In contrast, in the mast cell line CPII, both stimuli (PMA plus ionomycin) are necessary for promoter activation which, in a ddition, is sensitive to immunosuppressive drugs. Mapping of the TNF-a lpha promoter showed that in both cell types the so-called kappa 3 fac tor binding site is the crucial promoter element for the induction. We show that in DC18 cells, this sequence is bound to and controlled by NF-kappa B proteins p50 (NF-kappa 1) and p65 (RelA), whereas in CPII m ast cells, NF-AT and AP1 factors are the predominant proteins that bin d to and control the kappa(3) element of the TNF-alpha promoter. These and further experimental data indicate that in DC, NF-kappa B factors play a predominant role in the activation of the TNF-alpha promoter a nd, possibly, of other cytokine promoters.