A pilot study of colonic B cell pattern in irritable bowel syndrome

Objective. Low-grade gastrointestinal inflammation has been reported in patients with irritable bowel syndrome (IBS). However, the colonic B-cell pattern has not been investigated in these patients. Therefore, the aim of this pilot study was to investigate the distribution and isotype of immunoglobulin-producing B cells in the colonic mucosa of IBS patients. Material and methods. Patients with IBS (n=12) fulfilling the Rome II criteria were compared with controls (n=11). Immunohistochemical staining of biopsies from the sigmoid and ascending colon was performed. Results. The number of IgA+ B cells in the ascending colon was lower in IBS patients than in controls (p=0.039). Furthermore, unlike controls, IBS patients had a reduction of IgA+ B cells in the ascending colon relative to the sigmoid colon (p=0.04). Neither the IgG+, nor the IgM+ colonic B-cell numbers differed between IBS patients and controls. Very few colonic IgE+ cells were detected and there was no difference between the two subject groups. Conclusions. The reduced number of colonic IgA+ B cells in IBS patients suggests that the disorder may be associated with a modified gut immune defence. Whether this phenomenon is causally related to symptoms remains unknown and merits further investigation in a larger group of patients.