Decreased levels of gene transfer in naive PB T cells can be overcome by increasing the number of exposures to retroviral supernatant.

(A) CD45RA and CD45RO expression on freshly purified adult PB T cells was monitored by FACS analysis. The percentage of positive cells is indicated. (B) FACS-purified CD5⁺, CD5⁺/CD45RO⁻(RA⁺), and CD5⁺/CD45RA⁻(RO⁺) cells, stimulated for 2 days with immobilized anti-CD3 and anti-CD28 antibodies, were transduced either once or twice with LZRS-EGFP retroviral supernatants on fibronectin-coated plates. The T cells used in the 2 experiments presented here were isolated from different donors. The percentage of EGFP⁺ cells and the level of EGFP expression (MFI) are indicated.