Another example of immunofluorescence, this one used to detect the presence of one kind of autoantibody, "anti-nuclear antibody" (ANA) in serum, a diagnostic marker for various autoimmune diseases. The patient's serum is placed onto human HEp-2 cells on a microscope slide, then overlayed with a fluorescein-labelled anti-human IgG antibody. The presence of ANA is indicated by the green visible stain over the cell nuclei.