DISTINCT PATTERNS OF IMMUNOGLOBULIN CLASSES AND IGG SUBCLASSES OF AUTOANTIBODIES IN PATIENTS WITH INFLAMMATORY BOWEL-DISEASE

Objective: The pathophysiological significance of autoantibodies in in flammatory bowel diseases (IBD) is still unclear. To assess specific i mmunological abnormalities we examined the distribution and restrictio n of immunoglobulin classes and subclasses of anti-neutrophil cytoplas mic antibodies (ANCAs) in ulcerative colitis and of antibodies to panc reatic juice (APJs) in Crohn's disease. Methods: 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 a ntibodies in an immunofluorescence assay with human granulocytes or pa ncreas as substrate. Twenty-five patients with Wegener's granulomatosi s were used for comparison. Results: In ulcerative colitis ANCAs were found in 74% of the patients. They were predominantly of the Ige (96%) and IgA class (37%). In Crohn's disease APJs (present in 28% of the c ases) were of the Ige (98%) and IgA class (71%). ANCAs in ulcerative c olitis 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 Ige subclass es in ulcerative colitis or Crohn's disease. Conclusion: The immunoglo bulin classes and Ige subclasses of autoantibodies in ulcerative colit is and Crohn's disease differ from each other and from the distributio n of autoantibodies in vasculitic diseases (Wegener's granulomatosis, microscopic vasculitis, systemic lupus erythematosus). These alteratio ns reflect specific pathophysiological features of ulcerative colitis and Crohn's disease.