CD19 and infection: By using lentiviral vectors and transducing at a multiplicity of infection (M.O.I.)of 5, we achieved a high level (∼ 68%) of CD19-BBζ CAR expression in primary human T cells, and the mean fluorescence intensity (MFI) of CAR staining in the transduced T cells was much higher than in untransduced T cells (Fig. 1C).