Define and describe direct immunofluorescence of the skin.

Direct immunofluorescence (DIF) of the skin is a histologic stain for antibodies or other tissue proteins in skin biopsy specimens. A skin sample obtained from the patient is immediately frozen in liquid nitrogen or placed in special media to preserve the immunoreactants. Arrangements should be made to ensure proper and timely transport to the immunofluorescence laboratory. Once received, the tissue is sectioned and then incubated with antibodies to human immunoglobulins or complement components that have been tagged with a fluorescent molecule to allow their visualization. The samples are then examined with a fluorescence microscope, where fluorescence indicates that immunoreactants were deposited in the patient’s tissue. The specific immunoreactants present, and the pattern and intensity of staining, are used to determine the diseases most likely to be associated with the DIF findings.

Zillikens D: Diagnosis of autoimmune bullous skin disease, Clin Lab 54:491–503, 2008.