Direct immunofluorescence microscopy

Direct immunofluorescence plays an important role in the diagnosis of autoimmune blistering diseases. The purpose of direct immunofluorescence microscopy is to detect in vivo antibodies in patient's skin or mucosa. Direct immunofluorescence of pemphigus shows depositions of immunoglobulins and/or complement on the epithelial cell surface of keratinocytes, whereas pemphigoid shows linear deposition of immunoglobulins along the epidermal basement membrane zone. This linear deposition can be separated in an n-serrated pattern and a u-serrated pattern. An n-serrated pattern is seen in blistering diseases with binding above the lamina densa with antibodies against hemidesmosomal components, e.g. bullous pemphigoid, while a u-serrated pattern points to a sublamina densa binding diseases caused by autoantibodies against type VII collagen, e.g. epidermolysis bullosa acquisita. Finally, dermatitis herpetiformis shows a granular IgA deposition along the epidermal basement membrane zone.