Mucosal cytokine production in small-intestinal bacterial overgrowth

Scand J Gastroenterol. 1996 Oct;31(10):977-84. doi: 10.3109/00365529609003117.


Background: Mucosal production of interferon-gamma, interleukin-6, and tumour necrosis factor-alpha is increased in inflammatory bowel disease and parallels disease activity. Interferon-gamma production is also increased in coeliac disease. Conversely, local cytokine profiles have not been investigated in small-intestinal bacterial overgrowth. This study addressed this issue.

Methods: Eighteen adult subjects were studies with culture of proximal small-intestinal luminal secretion and measurement of luminal interferon-gamma, interleukin-6, and tumour necrosis factor-alpha concentrations by enzyme-linked immunosorbent assay. Small-intestinal histology was assessed by light microscopy.

Results: Interferon-gamma, interleukin-6, and tumour necrosis factor-alpha were measurable in proximal small-intestinal luminal secretions of all subjects, even in the absence of light microscopic evidence of enteropathy. Small-intestinal bacterial overgrowth was present in 12 of 18 (66.7%) subjects. Luminal concentrations of neither interferon-gamma nor tumour necrosis factor-alpha differed significantly in subjects with and without small-intestinal bacterial overgrowth (P + 0.06 and P = 1.0, respectively). Conversely, luminal interleukin-6 concentrations were significantly increased in subjects with this disorder (P = 0.02). Multivariate linear regression analysis suggested that colonic-type rather than salivary-type flora mediated this increased interleukin-6 response (P = 0.02 and P = 0.64, respectively). No correlation was found between luminal interleukin-6 and tumour necrosis factor-alpha concentrations, even after the confounding influence of colonic-type bacteria was excluded (P = 0.60).

Conclusions: These findings suggest that increased mucosal production of interleukin-6 occurs in small-intestinal bacterial overgrowth, particularly when the overgrowth flora includes colonic-type bacteria. Conversely, luminal levels of neither interferon-gamma nor tumour necrosis factor-alpha are increased in the circumstance, distinguishing the local cytokine profile in this disorder from those that occur in coeliac disease and inflammatory bowel disease.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Colony Count, Microbial
  • Cytokines / analysis
  • Cytokines / metabolism
  • Endoscopy, Gastrointestinal
  • Enzyme-Linked Immunosorbent Assay
  • Humans
  • Interferon-gamma / analysis
  • Interferon-gamma / metabolism*
  • Interleukin-6 / analysis
  • Interleukin-6 / metabolism*
  • Intestinal Diseases / metabolism
  • Intestinal Diseases / physiopathology
  • Intestinal Mucosa / metabolism*
  • Intestinal Mucosa / microbiology
  • Intestinal Mucosa / pathology
  • Intestine, Small / metabolism
  • Intestine, Small / microbiology*
  • Intestine, Small / pathology
  • Linear Models
  • Middle Aged
  • Multivariate Analysis
  • Regression Analysis
  • Tumor Necrosis Factor-alpha / analysis
  • Tumor Necrosis Factor-alpha / metabolism*


  • Cytokines
  • Interleukin-6
  • Tumor Necrosis Factor-alpha
  • Interferon-gamma