B-Cell Epitopes of Intracellular Autoantigens: Myth and Reality

Patients with systemic autoimmune diseases often develop autoantibodies directed against large intracellular complexes composed of a number of proteins that are non-covalently associated with nucleic acid components. For example, antibodies against nucleosomes, a complex of double stranded DNA and histones, are typically found in Systemic Lupus Erythematosus (SLE) patients. Antibodies targeting spliceosomes, the complex of small nuclear RNAs (snRNAs) or uridine rich RNAs (URNAs) with (Sm) and (RNP) proteins involved in the processing of RNA, are found in SLE and Mixed Connective Tissue Disease (MCTD) patients. Similarly, antibodies against the Ro ribonucleoprotein complex that consist of Ro and La proteins bound to small cytoplasmic RNAs (YRNAs) are most commonly detected in primary Sjogrenís Syndrome (pSS) and SLE; whereas, antibodies to topoisomerase I, an enzyme involved in the DNA duplication process, are found in patients with Systemic Scleroderma (SCL) ( 1 , 2 ).