title: Immunofixation reveals an apparent alpha heavy chain caused by precipitation of fibrinogen with IgA antiserum.
abstract: BACKGROUND
  Fibrinogen present in serum specimens can interfere with the interpretation of serum protein electrophoresis. We report here the unexpected precipitation of fibrinogen by an IgA antiserum used in immunofixation electrophoresis.
  
  
  METHODS
  Immunofixation electrophoresis of plasma combined with ethanol precipitation, serial dilution of plasma, and fibrinogen adsorption of the antiserum were used to investigate the apparent immunoreactivity of a commercial source of IgA antiserum to fibrinogen.
  
  
  RESULTS
  Fibrinogen immunoreactivity by IgA antiserum was observed at fibrinogen concentrations > or =0.93 g/l. Ethanol precipitation of plasma removed fibrinogen and prevented the immunofixation of the protein by the IgA antiserum. Adsorption of the IgA antiserum with human fibrinogen removed its ability to precipitate fibrinogen, demonstrating cross-reactivity between the IgA antiserum and fibrinogen.
  
  
  CONCLUSIONS
  Commercial sources of antiserum used for immunofixation electrophoresis may contain antibodies with specificity towards proteins typically absent from serum such as fibrinogen and can produce clinically misleading results.
authors.affiliation: University of North Carolina at Chapel Hill, School of Medicine, Department of Pathology and Laboratory Medicine, CB #7525, Chapel Hill, NC 27599, USA.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Snyder
authors.forename: Monte S
authors.initials: MS
authors.lastname: Willis
authors.forename: David G
authors.initials: DG
authors.lastname: Grenache
mesh_terms: D005260:Female; D005340:Fibrinogen / Q000737:chemistry* / Q000276:immunology*; D006801:Humans; D007137:Immunoglobulin alpha-Chains / Q000097:blood* / Q000276:immunology*; D047468:Immunoprecipitation; D008875:Middle Aged
chemical_list: D007137:Immunoglobulin alpha-Chains; D005340:Fibrinogen