title: An actin-myosin functional assay for analysis of smooth muscle (anti-microfilament) autoantibodies in human plasma.
abstract: The detection of serum autoantibodies to smooth muscle (SMA) on rodent gastric mucosa by indirect immunofluorescence (IIF) has long been an immunodiagnostic marker for autoimmune hepatitis type 1 (AIH-1). The reactive antigenic moieties are cytoskeletal proteins which include polymeric F-actin as judged by the staining of microfilaments of tissue by IIF. However, their specificity for actin in AIH-1 can be and usually is uncertain. Using an in vitro functional assay, we compared the effects of Fab fragments of immunoglobulin (IgG) prepared from SMA-positive plasma from two patients with the effects of Fabs from 10 healthy subjects. Fabs are incorporated into an assay where actin (the putative antigen) activates skeletal muscle heavy meromyosin (HMM) ATPase activity. The data from these functional assays provide new insights into the significance of anti-microfilament assays in the diagnosis, and perhaps also pathogenesis, of AIH-1.
authors.affiliation: School of Medical Sciences, Bosch Institute , The University of Sydney, Sydney NSW 2006, Australia.
authors.forename: R
authors.initials: R
authors.lastname: Martinez-Neira
authors.forename: C G
authors.initials: CG
authors.lastname: dos Remedios
authors.forename: I R
authors.initials: IR
authors.lastname: Mackay
mesh_terms: D008841:Actin Cytoskeleton / Q000276:immunology*; D000199:Actins / Q000502:physiology*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D001323:Autoantibodies / Q000097:blood*; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D009130:Muscle, Smooth / Q000276:immunology*; D015879:Myosin Subfragments / Q000378:metabolism*
chemical_list: D000199:Actins; D001323:Autoantibodies; D007140:Immunoglobulin Fab Fragments; D015879:Myosin Subfragments; D000251:Adenosine Triphosphatases