CD33 wild-type protein expression of parental and transduced cell lines. CD33 cell surface staining intensity, represented by the mean fluorescence intensity of cells stained with monoclonal anti-CD33 antibody (after subtraction of the mean fluorescence intensity of cells stained with isotype control antibody) of (A) murine 32D, (B) human OCI-AML3, and (C) human KG-1a cells. Results from one representative experiment are shown for each cell line. MOI denotes multiplicity of infection. Fluorescence intensity values cannot be directly compared between cell lines, because the brightness of the staining of CD33-transduced OCI-AML3 cells required data acquisition with modified voltage parameters.