title: Anticytokeratins are a potential source of false-positive indirect immunofluorescence assays for C-ANCA.
abstract: Antibodies to neutrophil cytoplasmic antigens (ANCA) targeted toward granule enzymes have been recognized as a valuable diagnostic tool in the detection of Wegener's granulomatosis and systemic vasculitides. However, the most commonly used method of detection, the indirect immunofluorescence assay, is prone to false-positive results due to antibodies of different pathological significance either targeted to, or cross-reacting with, similarly distributed epitopes. Using double immunofluorescence, the present study demonstrates that anticytokeratin antibodies are able to produce false-positive C-ANCA immunofluorescence assays. In addition, a case of natural appearance of cytokeratin-reactive antibodies causing a false-positive "pseudo-ANCA" staining pattern in a patient presenting with sepsis is reported. Since the expression of cytokeratins is almost exclusively confined to epithelial cells, the most plausible explanation for both phenomena is a crossreaction of anticytokeratin antibodies with granule associated epitopes. Due to the natural appearance of anticytokeratin antibodies in association with a variety of other pathologic entities, it is of crucial importance for the diagnostic significance of the C-ANCA immunofluorescence assay to exclude anticytokeratin caused false-positive results. It is shown that supplementary indirect immunofluorescence tests performed on cultured human epithelial cells readily distinguish anticytokeratin caused "pseudo-ANCA" from true C-ANCA.
authors.affiliation: Department of Anatomy, University of Vienna, Austria. Johannes.Streicher@univie.ac.at
authors.forename: J
authors.initials: J
authors.lastname: Streicher
authors.forename: B
authors.initials: B
authors.lastname: Fabian
authors.forename: K
authors.initials: K
authors.lastname: Herkner
authors.forename: H
authors.initials: H
authors.lastname: Pointner
authors.forename: P M
authors.initials: PM
authors.lastname: Bayer
mesh_terms: D019268:Antibodies, Antineutrophil Cytoplasmic / Q000097:blood* / Q000276:immunology; D001323:Autoantibodies / Q000276:immunology*; D003429:Cross Reactions; D004797:Enzyme-Linked Immunosorbent Assay; D005189:False Positive Reactions; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D007633:Keratins / Q000276:immunology*; D008875:Middle Aged; D009504:Neutrophils / Q000737:chemistry
chemical_list: D019268:Antibodies, Antineutrophil Cytoplasmic; D001323:Autoantibodies; D007633:Keratins