Immunocytochemical demonstration of lineage-specific cell marker expression of infected cultures. Cytospins of day-12 colony assays from human CB cells infected with a control (A,C,E) or mut10 carrying vector (B,D,F) were subjected to immunocytochemical staining. Mut10-transduced cells with an abnormal promyelocytic morphology exhibit a promiscuously positive immunoreactivity for myeloperoxidase (99% positive; B), lysozyme (76% positive; D), and glycophorin A (71.6% positive; F). The control cells show a lineage restricted immunoreactivity of myeloperoxidase (A), lysozyme (C), or glycophorin A (E) in promyelocytic, monocytic, and erythroid cells, respectively. Original magnification, × 560.