Another example of the indirect fluorescent antibody test is the test for antibodies against the measles virus. Inactivated measles virus-infected cells (the known antigen) are fixed to a microscope slide. The patient's serum is then added. If the person has measles, antibodies of the isotype IgG will be made against the measles virus and will bind to viral epitopes on the know measles virus-infected cells. After washing the slide to remove any unbound IgG, fluorescent antihuman IgG is added. The fluoprescent antihuman IgG then binds to the patient's IgG that is bound to the infected cells. When viewed with a fluorescent microscope, the infected cells will fluoresce green. Syncytia are fused virus-infected cells.

Indirect Immunofluorescence for Detection of Measles Antibody.
Kristina M. Obom, Patrick J. Cummings, Maria A. DeBernardi, Gary Brooker, authors.
Licensed for use, ASM MicrobeLibrary.