Smooth muscle autoantibodies with F-actin specificity.

Autoimmune hepatitis is a rare condition characterized by the presence of autoantibodies, among other features. Anti-smooth muscle autoantibodies with F-actin reactivity have long been considered specific markers of this disease, representing a valuable diagnostic element because they are distinctive of a subtype of autoimmune hepatitis: type 1. Indirect immunofluorescence is considered the best available method for detection of these autoantibodies, mainly because of its elevated sensibility, but it has some flaws: it is highly operator-dependent, and the standardization of the technique has not been achieved until now. We compared ELISA and Immunodot methods for confirming indirect immunofluorescence results in what concerns smooth-muscle autoantibodies' F-actin reactivity and concluded that ELISA is the most useful one. A new substrate is available for indirect immunofluorescence detection of anti-F-actin specificity, and seems to be a promising one, but further evaluation is needed.