Detection of Autoantibodies to Extractable Cellular Antigens

Abstract

When a sufficient number of antibody molecules are mixed with a soluble macromolecular antigen to which this antibody binds, large aggregates of antigen with antibody molecules occur which can be visualized in agar gel as a precipitin line (immunoprecipitation). The simplest way to indicate this reaction is to put the serum (antibody source) and the antigen source into separate wells on an agar gel and allow diffusion of antigen and antibody towards each other (Ouchterlony and Nilsson 1978). When antibody and antigen meet, they form a visible precipitin line (Ouchterlony gel immunodiffusion or Ouchterlony gel diffusion assay). This system is very valuable when: (1) the antigen is a macromolecular complex with many antibody binding sites; (2) the antigen source is a crude cellular (tissue) extract usually containing more than one antigen; (3) there is a need to examine the relatedness of unknown proteins in terms of their antigenic activity, using the patients’ sera as tools to study antigenic specificities; (4) the specificity of the antibodies in a serum is to be compared with the known specificity of the antibodies of a “control” serum (Janeway and Travers, 1996).