Alterations in serum anti-alpha-galactosyl antibodies in patients with Crohn's disease and ulcerative colitis.

Anti-galactosyl alpha1-3-galactosyl (anti-Gal) is a natural serum antibody abundantly produced in humans in response to immune stimulation by enteric bacteria. Marked elevation of its titer has been detected in parasitic diseases and in some autoimmune disorders. Because persistent intestinal infection and defective mucosal barrier have been suggested as potential etiologic agents of inflammatory bowel disease, the aim of this study was to analyze the sera levels of anti-Gal antibodies in patients with Crohn's disease and ulcerative colitis. An ELISA assay was performed to analyze circulating antibody using the disaccharide Gal (alpha 1-3)Gal coupled to human serum albumin as antigen and alkaline phosphatase-conjugated rabbit anti-human immunoglobulin G, A, M as antibody. Immunoglobulin classes were assayed using class-specific antibodies. The optical densities of sera from Crohn's disease (1.83 +/- 0.63) and ulcerative colitis (1.45 +/- 0.7) were significantly higher (P < 0.0001 and P < 0.0005, respectively) than those of the control group (0.97 +/- 0.39). In Crohn's disease the increase was distributed among the three immunoglobulin classes; in ulcerative colitis a significant increase was observed only for immunoglobulin A. The increased levels of circulating antibodies against Gal (alpha 1-3)Gal in the presence of intestinal bacterial strains expressing antigenic epitopes and breakdown of mucosal barrier could contribute to the dysregulated immune response observed in inflammatory bowel disease.