In the simplest form of direct immunofluorescence, an antibody molecule that recognizes a specific antigen, (such as a pathogen surface protein) is coupled to a fluorescent marker. If the antibody finds its target in a patient sample assay, the result can be detected under a microscope or in a fluorescent plate reader. The assay can be used for tissue testing (fluorescence microscopy), serum testing (reports on drugs, pathogens, acute phase proteins), FACS analysis and a host of other applications. In the Indirect Fluorescence configuration, the fluorescent marker is coupled to an anti-immunoglobulin. The primary immunoglobulin designed to react with molecule in the patient's sample is the marker's target. The larger immune complex that results from a positive test is more easily detected through amplification of the reaction.

Actual microscopic appearance.

Biomedical Laboratory Animations Last modified 11-15-03.

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