Kinetics of IL-6 mRNA expression after in vitro rhG-CSF stimulation. Purified PMNs from a normal donor were treated in vitro for 30 minutes to 24 hours with 10 ng/mL rhG-CSF. Total cellular RNA was isolated, reverse-transcribed, and PCR-amplified using IL-6–specific primers as described in the Materials and Methods. RNA integrity was evaluated in all experiments using β-actin primers. This is a representative gel from four experiments performed. The trend of IL-6 mRNA induction after rhG-CSF treatment was consistent across all donors evaluated with minor variations in the time of rhG-CSF stimulation necessary before seeing detectable IL-6 mRNA.