H/F-LV transduction does not facilitate VSVG-LV transduction. (A) Freshly isolated adult quiescent T and B cells were transduced with VSVG-LVs coding for the monomeric red fluorescent protein (VSVG-mRPF) at an MOI of 50, H/F-LV coding for GFP (H/F-GFP) at an MOI of 10, or with both vectors simultaneously. At day 3 after transduction mRFP versus GFP expression was measured by FACS. (B) T cells were preactivated through the T-cell receptor by incubation with anti-CD3 and anti-CD28 antibodies in the presence of rIL-2, whereas B cells were preactivated with SAC and rIL-2 for 24 hours before they were subjected to the same transduction protocol as indicated in panel A. (C) Freshly isolated adult quiescent T cells were transduced with H/F-LVs and VSVG-LVs as indicated in panel A. Percentages of mRFP⁺ versus GFP⁺ cells from single transductions or double transductions are indicated as determined by FACS (mean ± SD; n = 4). (D) Freshly isolated adult quiescent B cells were subjected to the same protocol as indicated in panel A. The percentage of mRFP versus GFP expression from single transductions or double transductions are indicated (mean ± SD; n = 4).