Anti-actin IgA antibodies in severe coeliac disease

Abstract

Anti-actin IgA antibodies have been found in sera of coeliacs. Our aim was to define the prevalence and clinical significance of anti-actin IgA in coeliacs before and after gluten withdrawal. One hundred and two biopsy-proven coeliacs, 95 disease controls and 50 blood donors were studied. Anti-actin IgA were evaluated by different methods: (a) antimicrofilament positivity on HEp-2 cells and on cultured fibroblasts by immunofluorescence; (b) anti-actin positivity by enzyme-linked immuosorbent assay (ELISA); and (c) presence of the tubular/glomerular pattern of anti-smooth muscle antibodies on rat kidney sections by immunofluorescence. Antimicrofilament IgA were present in 27% of coeliacs and in none of the controls. Antimicrofilament antibodies were found in 25 of 54 (46%) coeliacs with severe villous atrophy and in three of 48 (6%) with mild damage (P < 0.0001). In the 20 patients tested, antimicrofilaments IgA disappeared after gluten withdrawal in accordance with histological recovery. Our study shows a significant correlation between antimicrofilament IgA and the severity of intestinal damage in untreated coeliacs. The disappearance of antimicrofilament IgA after gluten withdrawal predicts the normalization of intestinal mucosa and could be considered a useful tool in the follow-up of severe coeliac disease.

Fig. 1

Case no. 4. Anti-microfilaments antibodies (titre 1 : 160) on fibroblasts (a, magnification 40×) and HEp-2 cells (b, magnification 40×) at initial dilution of 1 : 5 with antihuman IgA FITC conjugate as secondary antibodies. Typical positive actin stress fibres (microfilaments) appear as cytoplasmic parallel filaments. Negative effect on microfilaments staining on HEp-2 cells after absorption of serum with 500 µg of rabbit muscle actin. One hundred µl of absorbed serum at dilution of 1 : 5 was used (c, magnification 40×).

Fig. 2

IgA Anti-actin reactivity by ELISA of five anti-tTG/AAA/anti-MF positive sera. Mean of percentage (± standard deviation) of residual absorbance (optical density at 492 nm) is on the y-axis. Absorbance was reduced by preincubation with increasing amounts of actin, whereas it remained virtually unaltered by preincubation with tTG.

Fig. 3

IgA Anti-tTG reactivity by ELISA of five anti-tTG/AAA/anti-MF positive sera. Mean of percentage (± standard deviation) of residual absorbance (optical density at 450 nm) is on the y-axis. Preincubation with actin did not modify absorbance, which remained unaltered.