Serum secretory IgA, IgA1 and IgA2 subclasses in inflammatory bowel and chronic liver diseases

Healthy controls and patients with autoimmune chronic active hepatitis (CAH), primary biliary cirrhosis (PBC), coeliac disease (GSE), Crohn's disease (CD) and ulcerative colitis (UC) were examined for serum immunoglobulin A (IgA), secretory IgA (sIgA) and subclasses IgA1 and IgA2 concentrations separately. Elevated secretory IgA levels are found in CAH and PBC. IgA2 level as well as the proportional part of IgA2 out of the serum total IgA are significantly increased in GSE and in CD, while in UC IgA1 levels are significantly decreased as compared to controls. Serial determinations of IgA subclasses may provide a differential diagnostic tool in inflammatory bowel diseases and the findings support the view that increased sIgA levels in CAH and PBC probably have a different origin.