Stable and high level secretion of sTNFR-Fc in transduced cells. (A) Immunoblot detection of sTNFR-Fc protein in transfected cells. Mock = supernatant from mock transfected 293T cells; Intracellular = transfected cell lysate; and Secreted = supernatant from the transfected 293T cells. (B) Immunoblot detection of sTNFR-Fc protein in transduced cells intracellularly (cell lysate) and extracellularly (supernatant). HTB-T = transduced HTB-11 cells; CHME-T2 = CHME-5 cells transduced twice with the vector; CHME-T1 = CHME-5 cells transduced once with the vector. (C) Stable expression of sTNFR-Fc protein in conditioned medium of transduced cells. Expression of sTNFR-Fc in supernatants from transduced cells was measured by ELISA; results shown at different cell passages represent mean values from three independent experiments and error bars denote the standard deviation. (D) Stable expression of GFP in lentivirus vector-transduced cells. Transduced cells were passed in vitro and the percentage of GFP positive cells was determined every 5 passages by calculating the percentage of GFP+ cells within the culture using an inverted fluorescent microscope (Nikon Eclipse TE2000-U) with a digital camera attachment. Data presented here represent mean values from at least three independent experiments and error bars denote the standard deviation.