Nuclear localization effect of the GFP-MGMT* fusion protein in marked blood cells. Confocal microscopy image of GFP expression in peripheral blood (A) lymphocytes, (B) monocytes, and (C) granulocytes of in vivo–treated XSCID dog 1547. Note the green nuclei due to nuclear localization effect of MGMT* from the GFP-MGMT* fusion protein. Staining with an (A) anti-CD3 and (B-C) antineutrophil/antimonocyte monoclonal antibody with secondary red-Alexa Fluor–labeling confirms morphologic diagnosis.