Endocytosis of the TCR/CD3 complex upon transduction. (A-B) Downmodulation of CD3 (A) and TCR (B) on PBMC stimulated only with IL-2 and transduced with CD3-LVs (in absence of Vectofusin-1), VSV-LV, or left untransduced but activated (αCD3/αCD28). The mean fluorescence intensities measured were normalized to those of untreated nonactivated cells. N = 3 donors, mean ± standard error of the mean. *P < .05, **P < .01, ***P < .001 by 2-way ANOVA with Dunnett's correction. (C-D) Inhibition of endocytosis with Bafilomycin A1 (Bfla1) (C) or NH₄Cl (D) increases transduction efficiency on Jurkat cells with CD3-LVs. Mean ± SD of 3-4 independent experiments (E), or 1 experiment with 3 technical replicates (D). *P < .05, **P < .01, ****P < .0001 by unpaired Student t test. (E) Transduction of primary PBMC cultured in IL-2 by CD3-LVs upon treatment with Bfla1. N = 2 technical replicates from 1 donor, mean ± SD.