Bacteroides ovatusas the Predominant Commensal Intestinal Microbe Causing a Systemic Antibody Response in Inflammatory Bowel Disease

Abstract

To clarify what bacterial species of commensal intestinal microbes are recognized as the antigens that induce a serum antibody response in patients with inflammatory bowel disease (IBD), 72 subjects consisting of 12 Crohn’s disease patients, 30 ulcerative colitis patients, and 30 healthy volunteers were examined for their titers of serum antibody to these intestinal bacteria. In IBD patients, as a result, significant elevations of both the immunoglobulin G (IgG) and IgA titers toBacteroides ovatuswere found. Immunoblotting showed that a definite 19.5-kDa band ofB. ovatuswas bound to the serum antibody raised in IBD patients. It was thus concluded thatB. ovatuscauses serum antibody responses in IBD patients, and a 19.5-kDa molecule of this bacterium appears to be the responsible antigen, although the role of this event in pathogenesis remains unclear.