The total cellular RNA was isolated by using a TRIzol reagent (Gibco). One microgram of the RNA was reversed-transcribed using a cDNA synthesis kit (Boehringer Mannheim, Indianapolis, IN). The cDNA was then amplified in a 20 μL reaction mixture by PCR using the following conditions: 0.4 μM each primer, 0.2 mM deoxynucleoside triphosphate mixture (Perkin Elmer Corp., Foster City, CA), 50 mM KCl, 10 mM Tris-HCl (pH 8.3), 1.5 mM MgCl2, and 1 unit Taq polymerase (Perkin Elmer Corp.). The reaction mixtures were incubated in a thermal controller (Model PTC-100; MJ Research, Watertown, MA) for 35 cycles of denaturation for 45 seconds at 95°C, annealing for 1 minute at 58°C, and extension for 45 seconds at 72°C. The quantity of the amplified products was analyzed using an image documentation system (ImageMaster VDS; Pharmacia Biotech Inc., Uppsala, Sweden). The primer sequences specific to the genes examined and the predicted sizes for the human IL-6 cDNA were 5′-ACAGCCACTCACCTCTTCAG-3′ and 5′-GATGATTTTCACCAGGCAAG-3′, yielding a 214 bp amplification product. The primers used for the human β-actin cDNA were 5′-GTACAGTTGTTGGCGAGCA-3′ and 5′-TGCATCAGAAGTAAGCCTCTC-3′, yielding a 320 bp amplification product. All primer sequences were designed by using primer selection software offered through a web site (Primer 3; Center for Genome Research, the Whitehead Institute for Biomedical Research, Cambridge, MA; www.genome.wi.mit.edu).