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Chapter 48 : Immunofluorescence Methods in the Diagnosis of Renal and Skin Diseases
In many skin diseases, demonstration of immunoglobulin (Ig) or complement deposition in specific structures in the dermis and epidermis is an essential criterion for accurate diagnosis. For the skin, the focus is primarily on the immunofluorescence findings in bullous and connective tissue disorders, vasculitides, and other mucocutaneous conditions, for which this immunohistochemistry technique can provide useful diagnostic information. This chapter emphasizes the common immunofluorescence techniques used for diagnosis and interpretation with kidney and skin biopsy specimens. For skin specimens used for immunofluorescence studies, the proper choice of a biopsy site is critical to maximize the probability of obtaining diagnostic information. In most if not all cases of bullous skin diseases, namely, those autoimmune in nature, biopsy specimens should be obtained from perilesional tissue. For the diagnosis of pemphigoid, pemphigus, linear IgA bullous disease, epidermolysis bullosa acquisita (EBA), and dermatitis herpetiformis, the tissue sample should be taken from inflamed but unblistered skin. Most diagnostic studies using direct immunofluorescence techniques are performed with unfixed frozen tissue sections, since many antigens can be altered or destroyed by fixation. Indirect immunofluorescence is used to detect circulating autoantibodies with tissue specificity. These include anti-glomerular basement (anti-GBM) and anti-tubular basement antibodies in renal disease and bullous pemphigoid and pemphigus antibodies in skin disease. Photography is the only permanent record one has of the immunofluorescence findings. Many immunopathology laboratories are now using a digital camera interfaced with a computer to capture fluorescence images for documentation of results.
Direct immunofluorescence of a skin biopsy specimen. There is granular IgG deposition along the basement membrane zone. This pattern is characteristic of that seen in connective tissue disease-associated interface dermatitis, including lupus erythematosus.
Direct immunofluorescence of a skin biopsy specimen. There is fine linear wavy IgG deposition along the basement membrane zone. This pattern is characteristic of that seen in bullous pemphigoid.
Acute humoral rejection of a renal allograft. A three-step immunofluorescence technique shows diffuse C4d deposition (arrow) in peritubular capillaries.