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A predominant IgG 4 subclass may be responsible for false‐negative direct immunofluorescence in bullous pemphigoid
Author(s) -
Buschman Kerry E.,
Seraly Mark,
Thong H. Y.,
Deng JauShyong,
Draviam Rose P.,
Abernethy John L.
Publication year - 2002
Publication title -
journal of cutaneous pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.597
H-Index - 75
eISSN - 1600-0560
pISSN - 0303-6987
DOI - 10.1034/j.1600-0560.2002.290504.x
Subject(s) - subclass , bullous pemphigoid , staining , antibody , pemphigoid , immunofluorescence , immunoglobulin g , direct fluorescent antibody , pathology , immunology , microbiology and biotechnology , chemistry , medicine , biology
Background: Bullous pemphigoid (BP) is an immune‐mediated blistering disease, usually characterized immunopathologically by the linear deposition of IgG and C3 along the basement membrane zone (BMZ) of skin. However, positive deposition of C3 but negative staining for IgG on direct immunofluorescence (DIF) studies has been noted in some patients. Methods: Twelve patients known to have BP but with absence of staining for IgG were included in this study. Frozen sections of skin specimens from the 12 patients were subjected to IgG DIF, as well as a sandwich double antibody method of staining for IgG, IgG subclasses, and light chains. Enzyme‐linked immunosorbent assay (ELISA) using commercially available human IgG subclasses was used to analyze the subclass restriction of FITC‐labeled antihuman IgG conjugates. Results: Of the 12 skin specimens with positive C3 and negative IgG on DIF, nine were positive for IgG with the double antibody sandwich method. In addition, all 12 specimens had positive linear staining for the subclass IgG 4 along the BMZ with this method. There was no IgG light chain restriction. Two commercially obtained antihuman IgG conjugates, both commonly used in our laboratory for DIF testing, were analyzed for separate IgG subclass specificity by ELISA. Both conjugates showed high reactivity to IgG 1 and IgG 3 with less reactivity to IgG 2 and IgG 4 . Conclusion: These results suggest that the following factors contribute to false‐negative staining for IgG on DIF in some BP patients: (i): subthreshold IgG in skin specimens; (ii) limited reactivity of commercial antihuman IgG conjugates to the IgG 4 subclass; and (iii) decreased sensitivity of DIF compared with double antibody methods for the detection of IgG. The use of sandwich double antibody immunofluorescence methods to test for IgG and/or IgG subclasses may be helpful in definitively diagnosing BP in patients with negative IgG and positive C3 staining on DIF.