Introduction: Immunofluorescence (IF) is a laboratory technique introduced to dermatology in 1960s for the purposes of investigating the patophysiology and establishing the diagnosis of skin diseases, particularly autoimmune bullous diseases and connective tissues diseases. There are three basic types of IF techniques: the direct IF (DIF), which is used for the detection of antibodies and complement components fixed in the tissue, the indirect IF (IIF), which is used for the detection of circulating antibodies in patients' serum, and complement-fixed IIF (K-IIF), which is more sensitive in the detection of complement-binding circulating antibodies.
Autoimmune bullous diseases: Autoimmune bullous diseases (ABD) can be divided into two groups, depending on the site of blister formation: intraepidermal and subepidermal ABD. The detection of antibodies against the adhesion molecules by DIF technique in both groups of ABD has almost 100% diagnostic accuracy. The titer of circulating antibodies detected and measured by IIF correlates with the activity of pemphigus, but not with the pemphigoid. There are also two modified IIF techniques routinely used, split-skin DIF and IIF, both are most employed in differentiating of subepidermal ABD, since they share many clinical, histopathological and immunopathological features.
Connective tissue diseases: DIF test is most useful in diagnosing the connective tissue diseases (CTD), especially lupus erythematosus. Since there are false positive and negative results, DIF findings should be correlated with clinical histological and serological features.
Vasculitis: DIF test is used for detection of different immunoreactansts in leukocytoclastic vasculitis and Henoch-Schoenlein purpura.
Lichen planus, erythema multiforme: The characteristic pattern of fluorescence in DIF test can be found in most patients with these diseases.