What Are Smooth Muscle Antibodies?

Serum SMA in the normal population was negative and the titer was <1:10 (indirect immunofluorescence method). The SMA positive rate in the elderly is about 5%.

Anti-smooth muscle antibody (SMA) is an autoantibody with the body's smooth muscle tissue as the antigen. It has no organ and species specificity and is mainly of the IgG and IgM types. Tissues such as rat liver, kidney, human thyroid and platelets share common antigenicity with smooth muscle actin. Therefore, using purified myosin as an antigen, SMA can be detected by precipitation test, indirect hemagglutination test, radioimmunoassay and enzyme immunoassay. But the most commonly used indirect immunofluorescence method is to use smooth muscle as the antigen sheet.

Name: Anti-smooth muscle antibody

category: Immunology

Anti-smooth muscle antibody normal value

Serum SMA in the normal population was negative and the titer was <1:10 (indirect immunofluorescence method). The SMA positive rate in the elderly is about 5%.

Clinical significance of anti-smooth muscle antibodies

(1) SMA is mainly found in autoimmune (lupus-like) hepatitis, which can be used to distinguish it from SLE. The positive rate of this antibody is higher in primary biliary cirrhosis and chronic active hepatitis, but the serum SMA titer of the latter is very high. Low, the acute SMA positive rate can be as high as 80% in acute viral hepatitis, mostly appearing in the first week of onset.
(2) SMA is also found in other diseases, such as mycoplasma pneumonia, infectious mononucleosis, leprosy, children with skin and mucosal lymph node syndrome, syphilis, Sjogren's syndrome, rheumatoid arthritis, etc. People also have different degrees of positive detection rate.