Detection of luciferase expression in CD34⁺ cells by immunohistochemistry. Cytospin slides prepared from transduced CD34⁺ cells after 3 days of culture were stained with monoclonal antiluciferase antibody. Luciferase-positive cells have green cytoplasm; nuclei stained with DAPI are blue. Nontransduced, cultured CD34⁺ cells were used as a negative control. Original magnification, × 40.