ANTI-MICROFILAMENT IGG ANTIBODIES IN NORMAL ADULTS AND IN PATIENTS WITH AUTOIMMUNE-DISEASES - IMMUNOFLUORESCENCE AND IMMUNOBLOTTING ANALYSIS OF 201 SUBJECTS REVEALS POLYREACTIVITY WITH MICROFILAMENT-ASSOCIATEDPROTEINS

We have investigated IgG antibodies to microfilament-associated protei ns in sera from 29 normal controls and from 172 patients with autoimmu ne diseases such as rheumatoid arthritis (n = 45), systemic lupus eryt hematosus (n = 43), polymyositis/dermatomyositis (n = 36), systemic sc lerosis (n = 35), and autoimmune chronic active hepatitis (CAH, n = 13 ). We observed, by indirect immunofluorescence, a staining pattern in which the fluorescence was continuously distributed along microfilamen ts by using several animal and human cell lines as substrate. Because no reactivity with individual bands or specific combinations of bands was observed by immunoblotting using different cell lines, we further characterized our sera by immunoblotting using a panel of the purified microfilament-associated proteins filamin, myosin, alpha-actinin, act in, tropomyosin, and myosin light chain. Results shows that normal as well as autoimmune sera are polyreactive with microfilament proteins. The specificity of reactivity against a particular microfilament-assoc iated protein was demonstrated by inhibition experiments with the spec ific protein. No correlation was observed between immunoblot and immun ofluorescence results. Of the 201 sera, 40 (20%), 42 (21%), 31 (15%), 26 (13%), 34 (17%), 24 (12%), 4 (2%), and 0 (0%) reacted, respectively , by immunoblotting with 0, 1, 2, 3, 4, 5, 6, or 7 of the microfilamen t-associated proteins. Furthermore, 57 different profiles of reactivit y with the panel proteins were observed. All autoimmune CAH sera react ed with at least 3 proteins. This result was strikingly unique to this group. Anti-actin antibodies were as common in normal as in CAH sera. Anti-alpha-actinin antibodies were strikingly more frequent in CAH th an in any group. We conclude that a remarkable diversity of anti-micro filament antibodies is present in normal as well as in autoimmune sera and that a continuous microfilament fluorescent pattern is not restri cted simply to anti-actin antibodies. Furthermore, sera negative by im munofluorescence react with several microfilament-associated proteins by immunoblotting. Reactivity with multiple (greater than or equal to 3) microfilament-associated proteins including alpha-actinin distingui shes CAH sera from normal and other autoimmune sera. (C) 1995 Academic Press, Inc.