Immunoprecipitation assays for the detection of specific extractable nuclear antigen ​autoantibodies: a role in the modern immunology laboratory?

To the Editor,
Extractable nuclear antigens (ENAs) is a term given to soluble cellular antigens that are retrieved from cell lysates; antigen-specific autoantibodies are termed anti-ENA and include anti-Ro60, anti-La, anti-Scl70 and anti-Jo-1. Historically, liquid-phase immunoprecipitation (IP) assays such as double immunodiffusion (Ouchterlony) and counterimmunoelectrophoresis (CIEP) have been used to detect specific autoantibodies.1 In these assays, antigen and antibodies passively or actively diffuse, via electric currents, in a gel medium. As antigens are in their native form, there is less likelihood of distorting or obscuring relevant antigen epitopes or creating neo-epitopes than when an antigen is adsorbed to a solid surface...