Pseudomonas syringae pv. pisi for indirect fluorescence

Indirect immunofluorescence (IIF) relies on the use of antibodies to label a specific target antigen with an antibody. The primary antibody is unconjugated and recognizes the antigen, a secondary antibody directed against the primary antibody is used for detection. This secondary antibody is fluorescently labelled (also called fluorophores or fluorochromes) such as fluorescein isothiocyanate (FITC). ​The fluorophore allows visualization of the target distribution in the sample under a fluorescent microscope (eg epifluorescence and confocal microscopes).