Fig. 4. Inhibition of NF-B-mediated transcription by STAT6. HeLa cells were transiently transfected with pNF-B-luc together with various EGFP expression vectors. EGFP expression vectors expressing fusions with p65, STAT6 or both, or a control EGFP were transfected into the cells. Cells were pretreated for 40 minutes with either medium alone or 10 ng ml^-1 IL-4 (in medium) prior to treatment with 10 ng ml^-1 TNF for 6 hours. The luciferase activity in cell lysates was determined in pairs of samples treated either with TNF alone or with IL-4 and TNF. The relative luciferase activity obtained between these values reflects the level of inhibition obtained through prior stimulation with IL-4. These ratios are plotted as percentage inhibition for each different transfection condition. IL-4 treatment of EGFP-STAT6-expressing cells significantly inhibited transcription compared with all other transfection conditions (5% least significant difference). n=3, error bars±s.e.