Anti-RNP/Sm

Anti-RNP/Sm

Anti-RNP/Sm is an ELISA-based, automated, in-vitro test system for the quantitative determination of IgG antibodies against the RNP/Sm ribonucleoprotein complex in human serum or plasma.

The RNP/Sm complex is an extractable nuclear antigen (ENA) and is useful in the diagnosis of mixed connective tissue disorder (MCTD, Sharp syndrome) and related autoimmune diseases. The antigen is a multi-enzyme complex made of three U1-specific ribonucleoproteins (U1-A, U1-C, U1-70 kDa) and nine different Sm core proteins. Antibodies against the 70 kDa protein of this complex are a very specific marker for Sharp syndrome. Nearly all affected patients have autoantibodies against this target antigen; absence of RNP/Sm antibodies thus rules out this disease. The Sm proteins and the ribonuncleoproteins A and C are recognized by antibodies that also occur in cases of mixed connective tissue disorder and systemic lupus erythematosus. However, SLE patients generally have lower titres of antibodies against the 70 kDa protein than MCTD patients.