ANTI-ACTIN SPECIFICITY OF HUMAN SMOOTH-MUSCLE ANTIBODIES IN CHRONIC ACTIVE HEPATITIS

Abstract

Sera (30) reacting by IFL [immunofluorescence] technique in titers .gtoreq. 100 with smooth muscle fibers of rat stomach, rat renal glomeruli and with the membrane region of thyroid cells, were randomly chosen among sera sent in for routine testing of tissue antibodies. All sera but 1 were derived from patients with chronic active hepatitis. The smooth muscle and other relevant cell staining were abolished after absorption of sera with actin, prepared from rabbit skeletal muscle and found to be homogeneous by SDS [sodium dodecyl sulfate] gel-electrophoresis and by EM. The actin antibodies were purified by precipitation of sera with F[fibrous]-actin and elution of the precipitates at acid pH. The purified antibodies stained all tissues in the same way as the original sera. In double immunodiffusion tests, all 30 sera gave precipitation with actin. These broad-reacting SMA [smooth muscle antibodies] are directed against actin. The finding of high-titered SMA is of diagnostic value and supports the clinical diagnosis of active chronic hepatitis. Anti-actin antibodies eluted from human sera are a suitable tool for studying actin-containing cellular structures.