Routine diagnostic immunohistochemical labeling of extracellular antigens in formol saline solution-fixed,...

A technique involving modification of the routine paraffin embedding procedure that allows immunohistochemical examination of extracellular antigens by light microscopy is described. The method is thus suitable for routine diagnostic immunofluorescence studies, permitting reliable, reproducible immunolabeling of immunoglobulins and complement components usually not preserved by routine processing procedures. Immunoreactivity as measured by direct immunofluorescence and immunoenzymatic (peroxidase-antiperoxidase) histochemistry is comparable to results with fresh-frozen cryostat sections. Morphologic preservation is superior, however, and the processed material is suitable for routine hematoxylin-eosin staining.