CD34+ cord blood cells transduced with the MFM vector and expanded with AP1903 express the F36Vmpl transgene. Immunohistochemical staining was performed to identify cells that contain the HA epitope as part of the F36Vmpl transgene. (See “Materials and Methods” for a complete description of the method.) Cord blood cells were transduced with the MFM vector and then incubated in the presence (A) or absence (B) of AP1903 for 14 days prior to staining for the HA epitope. Panel C shows mock transduced cells incubated for 14 days and then stained for the presence of the HA epitope.