Significance of smooth muscle/anti-actin autoantibodies in celiac disease

Abstract

Background/aim: Smooth muscle antibody (SMA) specific for the protein actin, a major component of the cytoskeleton of epithelial cells, is one of the most prevalent non-organ specific autoantibodies in the serum of celiac disease (CD) patients. Our aim was to explore the clinical relevance of the presence of IgA type anti-actin antibody (AAA) and SMA in a series of patients with CD.

Methods: We evaluated frozen serum samples collected at diagnosis from 92 adult patients with CD and 52 control individuals in whom CD was excluded. Patients were re-evaluated a median time of 5 yr after treatment. IgA type AAA was detected using a modified commercial ELISA assay and IgA SMA was detected using indirect immunofluorescence on primate esophagus substrate.

Results: At diagnosis, samples from CD patients had significantly higher AAA values than controls (p<0.00001). While all active CD patients had serum AAA values over the cut-off for healthy controls, we observed a very significant reduction of these antibodies after treatment (p>0.0001). AAA had a highly significant correlation with both, tissue, transglutaminase (r=0.62) and antigliadin (r=0.60, p<0.00001) antibodies as well as the severity of the intestinal injury (p<0.05). SMA was detected in sera of 35 consecutive CD patients. At diagnosis, SMA positive patients had significantly higher values of AAA (p<0.0002), increased number of autoimmune disorders (p<0.04), delayed menarche (p<0.04), lower hemoglobin levels (p<0.01), increased fecal a-I antitrypsin clearance (p<0.01) and more severe diarrhea (p<0.06). We also detected a trend to more severe complications at follow-up (p=0.059).

Conclusions: Based on our findings we suggest that the presence of increased IgA AAA serum levels is a highly sensitive marker of the disturbed architecture of intestinal epithelial cells of CD patients with a potential relevance to diagnosis and follow-up. The presence of SMA seems to define a distinct subset of CD patients with a more severe clinical outcome.