Blood from a blood source is drawn into a fluid flow circuit. A mononuclear cell product is separated from the blood, followed by at least a portion of the mononuclear cell product being conveyed into an electroporation device without disconnecting the blood source from the fluid flow circuit. The electroporation device opens pores in a membrane of at least one of the cells of the mononuclear cell product to allow DNA material (which is added to the mononuclear cell product prior to electroporation) to enter and modify the genome of the cell. At least a portion of the modified mononuclear cell product is returned to the blood source. The mononuclear cell product may be washed prior to being conveyed into the electroporation device. The modified mononuclear cell product may be washed after exiting the electroporation device.
