Investigators from Wellington, New Zealand, examined the role of the mucosal immune system in the pathogenesis of irritable bowel syndrome.
Histologic and immunohistologic studies were performed on colonoscopic biopsy specimens from 77 patients with symptoms satisfying the Rome criteria and 28 asymptomatic control patients.
Histologic assessment of biopsy specimens from symptomatic patients indicated 3 different groups.
The first (n = 38) had normal conventional histology. However, immunohistology showed increased intraepithelial lymphocytes (median, 1.8-fold), lamina propria CD3+ cells (2-fold), and CD25+ cells (6.5-fold), compared with asymptomatic controls.
The second group (n = 31) had nonspecific microscopic inflammation. Immunohistology showed similar increases in lymphocyte populations, as well as increased numbers of neutrophil leukocytes and mast cells.
The third group (n = 8) fulfilled histologic and immunohistologic criteria for classic lymphocytic colitis.
| Immunohistology showed increases in activated immunocompetent cells.
| Gastroenterology |
Dr Vinton S. Chadwick, of the Wakefield Hospital, Wellington, said on behalf of colleagues, "Examination of colonoscopic biopsy specimens from irritable bowel syndrome patients showed subgroups with normal and abnormal conventional histology."
"All groups showed increased numbers of activated immunocompetent cells in the intestinal mucosa on quantitative immunohistology, implicating the mucosal immune system in pathogenesis," it was concluded.
In an accompanying Editorial, Stephen M. Collins, of the McMaster University Medical Center, Hamilton, Ontario, Canada, comments, "This article is an important contribution to our conceptualization of IBS.
"It promotes the hypothesis that, in at least in a subset of patients, low-grade inflammation and immune activation plays a pathophysiological role."
"The study requires confirmation and extension before attempts are made to extrapolate these findings to the IBS patient population at large," he concludes.