Antibodies targeting extractable nuclear antigens: historical development and current knowledge.

Abstract

The extractable nuclear antigens (ENA) are a heterogeneous group of ribonucleoproteins and non‐histone proteins with different functions in nuclear metabolism. The detection of antibodies targeting ENA is a well‐established tool in the diagnosis of autoimmune diseases such as lupus erythematosus (LE), progressive systemic sclerosis (PSS), polymyositis (PM), dermatomyositis (DM), mixed connective tissue disease (MCTD), Sjögren's syndrome (SS) and overlap syndromes. Descriptions of precipitin reactions between soluble tissue components and sera of patients suffering from these diseases, as well as identification of the antigen–antibody reactions, have been the subject of a large number of investigations in recent years. Most of the corresponding antigens have been identified (over 20 antigen systems) and knowledge about the clinical and genetic association of the antibodies detected has improved. Antibodies targeting ENA were first described in 1959, when Holman et al. recorded a precipitin reaction of sera from systemic LE (SLE) patients with extractable antigens isolated from crushed calf thymus.1 This observation was interpreted as an antigen–antibody reaction of autoantibodies in the SLE sera with soluble nuclear antigens. The nomenclature of an autoantibody to ENA depended on the group first describing it, and was made corresponding to the nuclear function of the antigen (RNP), the name of the patient providing the prototype serum (Ro, La, Sm, Jo, Mi) or the disease from which the serum donor suffered (SSA, SSB, SSC, Scl‐70, PM‐1, PM‐Scl).