CHME-5 and BV2 cells were cultured in Dulbecco Modified Eagle’s Medium (DMEM, Gibco) supplemented with 10% fetal bovine serum, penicillin-streptomycin (100 U/ml) and 2 mM l-glutamine. Transfections were carried out by Lipofectamine LTX (Invitrogen) according to the manufacturer’s instructions; the p277.pCCLsin.hPGK plasmid encoding for farnesyl-GFP (f-EGFP) was provided by Prof. Luigi Naldini (Università Vita-Salute San Raffaele, Milano). Peripheral blood mononuclear cells were separated from whole blood by density gradient centrifugation (Ficoll-PaqueTM Plus, GE Healthcare) and CD14+ monocytes were purified by immunomagnetic beads [immunomagnetic MicroBeads (MACS® Miltenyi Biotec)]. Monocytes were stimulated with cytokines 18 h after seeding. Blood samples came from three healthy donors recruited among the lab workers, who signed an appropriate informed consent. The study was approved by the local Ethical Committee.