Immunocytochemistry of undifferentiated and differentiated transfected HL-60 cells. Cytospin of undifferentiated (left panels) and DMSO/RA-differentiated (right panels) transfected HL-60 cells containing NGAL cDNA were fixed in 4% formaldehyde in 0.1 mol/L phosphate buffer, permeabilized with Triton X-100, and labeled with affinity-purified rabbit anti-NGAL antibody (2.5 μg/mL; upper panel) or anti-MPO antibody (76 μg/mL; lower panel).