Distinct patterns of immunoglobulin classes and IgG subclasses of autoantibodies in patients with inflammatory bowel...

The pathophysiological significance of autoantibodies in inflammatory bowel diseases (IBD) is still unclear. To assess specific immunological abnormalities we examined the distribution and restriction of immunoglobulin classes and subclasses of anti-neutrophil cytoplasmic antibodies (ANCAs) in ulcerative colitis and of antibodies to pancreatic juice (APJs) in Crohn's disease.

We tested 62 sera of patients with ulcerative colitis and 184 sera of patients with Crohn's disease for their immunoglobulin class and IgG subclass distribution of ANCAs (in ulcerative colitis patients) and APJs (in Crohn's disease patients) by fluorescence isothiocyanate (FITC)-labelled anti-human antibodies in an immunofluorescence assay with human granulocytes or pancreas as substrate. Twenty-five patients with Wegener's granulomatosis were used for comparison.

In ulcerative colitis ANCAs were found in 74% of the patients. They were predominantly of the IgG (96%) and IgA class (37%). In Crohn's disease APJs (present in 28% of the cases) were of the IgG (98%) and IgA class (71%). ANCAs in ulcerative colitis were of the IgG1 (73%) and IgG3 (5%) subclasses, APJs in Crohn's disease of the IgG1 (94%), IgG2 (20%) and IgG3 (2%) subclasses. The immunoglobulin class and IgG subclass distributions of ANCAs and APJs resembled the changes in total immunoglobulin classes and IgG subclasses in ulcerative colitis or Crohn's disease.

The immunoglobulin classes and IgG subclasses of autoantibodies in ulcerative colitis and Crohn's disease differ from each other and from the distribution of autoantibodies in vasculitic diseases (Wegener's granulomatosis, microscopic vasculitis, systemic lupus erythematosus). These alterations reflect specific pathophysiological features of ulcerative colitis and Crohn's disease.