Which tests are used in research labs to diagnosis bullous pemphigoid (BP)?

Updated: Oct 14, 2020
  • Author: Lawrence S Chan, MD; Chief Editor: Dirk M Elston, MD  more...
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Answer

Experimental procedures available in research laboratories include direct and indirect immunoelectron microscopy, immunoblotting, immunoprecipitation, and enzyme-linked immunosorbent assay (ELISA), as follows:

  • Direct and indirect immunoelectron microscopy: Direct and indirect immunoelectron microscopy (immunoEM) ultrastructurally localize in vivo–bound IgG autoantibodies (direct immunoEM) or the binding site of circulating IgG autoantibodies (indirect immunoEM) at the basement membrane. IgG autoantibodies are detected at the hemidesmosome/upper lamina lucida areas of the skin basement membrane.

  • Immunoblotting [60] : Immunoblotting or Western blotting demonstrates reactivity of IgG in the sera of patients with proteins extracted from healthy human skin. The sensitivity of immunoblotting varies. In 75% of patients, a reaction occurs with the BP230 antigen, while, in 50% of patients, a reaction occurs with the BP180 antigen.

  • Immunoprecipitation: Like immunoblotting, immunoprecipitation demonstrates reactivity with BP230 and BP180. Unlike immunoblotting, immunoprecipitation is performed with native, rather than denatured, protein and is more sensitive. Immunoprecipitation is more difficult to perform and generally less available than immunoblotting. In most cases, immunoprecipitation detects autoantibodies specific for BP230 and BP180.

  • Enzyme-linked immunosorbent assay: The ELISA technique analyzes the bullous pemphigoid antigen-specific IgG autoantibodies in the patients' sera by using various lengths of recombinant proteins of the BPAg1 or BPAg2 antigens. In several reports, ELISA has been demonstrated to be highly sensitive and specific. [61] ELISA kits for testing bullous pemphigoid antigen-specific IgG autoantibodies are now available commercially. However, only a few medical centers currently offer this service. ELISAs based on recombinant proteins encoded by BP230 and BP180 have been developed. [62] These assays are not commercially available, but they offer promise as investigational tools. An ELISA based on BP180 demonstrates sera reactivity with more than 90% of patients with bullous pemphigoid.

  • Immunohistochemistry: If freshly frozen tissue is not available for direct immunofluorescence microscopy, formalin-fixed skin sections from patients with bullous pemphigoid may be used to examine the presence of C3 deposition along the epidermal basement membrane zone, for the confirmation of the diagnosis. [63]


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