Recent clinical observations have assigned increased significance to the anti-Sm and anti-RNP antibodies found in the sera of patients with systemic lupus erythematosus (SLE) and certain other related disorders. The anti-Sm antibodies are highly specific for SLE, whereas the anti-RNP antibodies show a wider distribution and help define a new syndrome termed 'mixed connective tissue disease'. Considerable interest has centered on the character of the antigens recognized by these autoantibodies because of their probable involvement in the processing of transcribed RNA. It has been known for some years that they are present in the nuclei of a wide variety of cells and that RNP antigen is sensitive to RNase. Some work has been carried out on the isolation of these antigens with emphasis on their size, charge, and antigenicity. Very recently, considerably more insight has been gained from the work of Lerner and co-workers. Their work has identified the RNA precipitated by these two types of autoimmune sera, and differences in RNA composition were noted, although the same protein bands were precipitated by both types of sera. These results are difficult to relate to earlier studies that suggested a role for specific proteins in the differential reactivity of these sera. The present studies indicate that both Sm and RNP coexist in a single complex that can be dissociated to give clearly distinct antigenic proteins. The Sm determinants reside primarily on proteins of 25,000 and 16,000 daltons, whereas the RNP determinants reside at least in part on a protein of 19,000 daltons.
ASJC Scopus subject areas
- Immunology and Allergy