Cell lines were obtained from the German Collection of Microorganisms and Cell Cultures (Brunswick, Germany). All cells but retinal pigment epithelial (RPE) were cultured in RPMI-1640 medium (Invitrogen, Grand Island, NY) supplemented with penicillin/streptomycin and 10% fetal bovine serum. RPE cells were cultured in DMEM (Invitrogen, Grand Island, NY) medium supplemented with penicillin/streptomycin and 10% fetal bovine serum. Suspension and adherent cells were maintained at a density of 0.5–1 million cells/ml or 50–90% confluence, respectively, at 37 ºC in a humidified atmosphere with 5% CO2. Jurkat cells engineered to express GFP were generated by retroviral transduction as described.23 (link)–24 (link) Cell counts were measured using the Neubauer hemocytometer (Hausser Scientific, Horsham, PA), according to manufacturer’s instructions.