Class and subclass-associated specificity differences of anti-gliadin antibodies from mucosa and serum

The class and subclass distribution of antibodies against gliadin in intestinal lavage fluid, saliva and serum was investigated in individuals with coeliac disease. Serum antibodies against gliadin were mainly or even exclusively of the IgA1 subclass. In intestinal lavage fluid and saliva, antibodies of both IgA1 and IgA2 subclasses were found. In patients with and without IgA deficiency, an IgG response was detected both in serum and intestinal lavage fluid with a predominance of IgG1 in selected patients. Specific IgG2, IgG3 and IgG4 antibodies were also detected in intestinal lavage fluid, while no specific IgG2, IgG3 or IgG4 antibodies were found in serum, suggesting a local production of specific IgG antibodies. In Western blot analysis, intestinal lavage fluid and serum IgA antibodies reacted against gliadin components with a MW between 33,000 and 42,000. Serum IgA1 antibodies directed against a gliadin component with a MW slightly higher than 42,000 were also observed. Specific IgG and IgM antibodies in both the secretion and serum against gliadin components with a MW between 33,000 and 42,000 were also detected. This study shows that mucosa-derived gliadin-specific IgA and IgG antibodies may be produced even when there is an absence of specific antibodies of the corresponding immunoglobulin subclass in serum. Furthermore, the specificity of serum and intestinal lavage fluid anti-gliadin IgA1 antibodies may differ.