IgA subclass antibodies to gliadin in serum and intestinal juice of patients with coeliac disease.

Serum IgA anti-gliadin antibodies (AGA) were positive in 25 (68%) of 37 untreated adults with coeliac disease belonging mostly to IgA1 subclass (88%) and only in a few cases to IgA2 (12%). Antisecretory component IgA AGA were present in serum of seven patients (28%) by immunofluorescence and in nine (36%) by ELISA. The search for IgA AGA in jejunal juice of eight untreated children with coeliac disease was positive in seven cases (88%), with consistent finding of antisecretory component IgA AGA. These antibodies belonged with equal proportion to IgA1 and IgA2 subclasses. This study shows that in intestinal secretions of untreated coeliac disease cases the IgA immune response to gliadin is confined to polymeric anti-secretory component IgA with the same prevalence of IgA1 and IgA2 subclasses, while in serum IgA AGA are largely monomeric, more frequently of IgA1 than of IgA2 subclass, and with a lower proportion of polymeric anti-secretory component IgA (20-36%). The finding of secretory IgA AGA in serum of patients with coeliac disease could result from a spill-over from the intestinal mucosal synthesis into the circulation.