IP-10 mRNA expression is controlled at the level of transcription. (A) TG-elicited macrophages were treated with LPS (10 ng/mL) for various times in the absence or presence of IL-10 (25 ng/mL) before isolation of nuclei and analysis of transcription by nuclear run-on. Radiolabeled nuclear RNA was hybridized with nylon membranes containing equivalent amounts of denatured plasmid DNA encoding IP-10 and tubulin (top panel). (B) Slot blots shown in the top panel were quantified by phosphorimage analysis and levels of IP-10 transcript normalized for levels of tubulin. Similar results were obtained in three separate experiments.