Enzyme immunoassay for the detection of autoantibodies IgG against Sm.
Uracil-rich, small nuclear RNAs (U-snRNA) are physiologically complexed with proteins to form ribonucleoprotein particles (U-snRNP) which are involved in the splicing process of pre-mRNA. Different complexes (U1-U6) can be distinguished according to the participating RNA; their protein components are in part common, in part different.
Sm auto-antibodies (so-called according to the first described patient Smith) are directed against those proteins that are common to most RNPs. The largest ones, B, B' and D (28, 29 bzw. 16 kDa), are the most important antigenic targets. Sm antibodies are highly specific for systemic lupus erythematosus (SLE) but exhibit only limited sensitivity (prevalence < 30%).
The EULISA Sm IG is intended for the quantitative or qualitative determination of IgG antibodies in human serum, directed against Sm. The immobilised antigen is a mixture of the most abundant Sm-D polypeptide subtypes, all of them isolated from bovine thymus. Sm-B/B’ polypeptides are absent in the preparation since autoantibodies against the U1-RNP specific proteins A and C (primarily indicative for mixed connective tissue disease (MCTD)) tend to cross-react with these auto-antigens.
The test is fast (incubation time 30 - 30 - 30 minutes) and flexible (break apart wells, ready-to-use reagents). Six calibrators allow quantitative measurements; a negative and a positive control to check assay performance.
Contents of the kit
All kit components are stored at 2 - 8°C.