IL-6 mRNA expression by PMNs analyzed by RT-PCR. Total cellular RNA was isolated from purified PMNs from a normal donor (the PMNs were maintained in culture media for 24 hours before RNA extraction; lane 1), PMNs from a normal donor treated for 24 hours in vitro with rhG-CSF (lane 2), or PMNs from a patient treated with rhG-CSF in vivo (lane 3). RNA was reverse-transcribed and PCR-amplified using IL-6–specific primers as described in the Materials and Methods. RNA integrity was checked using β-actin primer. This is a representative gel from four experiments performed.