Nucleoprotein autoantibodies in lupus erythematosus

Autoantibodies against deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) proteins are commonly detected in patients with lupus erythematosus (LE). Antibodies against native DNA are frequently detected in a subset of LE patients with a high prevalence of renal disease. Single-stranded DNA antibodies are also commonly detected in patients with systemic lupus erythematosus (SLE) but recent evidence indicates that approximately 25% of patients with benign, cutaneous (discoid) lupus also possess single-stranded DNA IgM autoantibodies. LE patients also frequently possess antibodies directed against a variety of ribonuclear proteins (RNP). These RNA protein autoantibodies are generally divided into two groups. One group is termed snRNPs (small nuclear ribonuclear protein); the other is termed scRNPs (small cytoplasmic ribonuclear protein). Anti-RNA protein autoantibodies occur as frequently in patients with SLE as do native DNA antibodies. Furthermore, in contradistinction to nDNA antibodies, lupus patients generally make large quantities (detected by gel precipitin techniques) of anti-RNP antibodies. The anti-RNP antibodies are directed against proteins that bind with specific RNA nucleotides. The best evidence at present indicates that these RNA proteins containing the specific RNA nucleotides are involved in RNA processing and post-translational activities such as protein synthesis. Furthermore, these SLE autoantibodies are now being employed, together with other autoantibody systems detected in other connective tissue diseases, to define the biological role of the respective RNA proteins.