Antibodies in human serum that precipitate ribonuclease P.

Sera from certain patients with systemic lupus erythematosus (SLE) and related rheumatic diseases contain antibodies that selectively deplete extracts of HeLa cells of RNase P activity. Most of the sera that recognize RNase P, an endoribonuclease with an essential RNA subunit, also contain antibodies against another small ribonucleoprotein known as the Th antigen. A species of RNA about 400 nucleotides in length is the only RNA species found in common in all immunoprecipitates prepared with anti-RNase P antibodies. The discovery of antibodies against RNase P defines a major class of antibodies produced by patients with autoimmune disease.