Stimulation of endothelial cells with IL-4 or OSM does not activate NF-κB. Nuclear extracts from HUVEC or BAEC incubated for 4 hours in the presence or absence of 100 U/mL TNF-α, 10 ng/mL IL-4, or 10 ng/mL OSM were incubated with a radiolabeled oligonucleotide containing the κB element from the murine H-2K^b gene. DNA-protein complexes were analyzed by a gel mobility shift assay, followed by autoradiography. The arrow marks the inducible complex containing the p50/p65 heterodimeric NF-κB protein. Complex formation was inhibited by an excess of unlabeled oligonucleotide, confirming its specificity (data not shown).