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Gut 47:79-87 doi:10.1136/gut.47.1.79
  • Inflammation and inflammatory bowel disease

Non-pathogenic bacteria elicit a differential cytokine response by intestinal epithelial cell/leucocyte co-cultures

  1. D Hallera,b,
  2. C Bodea,
  3. W P Hammesb,
  4. A M A Pfeiferc,
  5. E J Schiffrinc,
  6. S Blumc
  1. aInstitute of Biological Chemistry and Nutrition Science, University Hohenheim, Germany, bInstitute of Food Technology, University Hohenheim, Germany, cImmunology, Nestlé Research Centre, Lausanne, Switzerland
  1. Dr S Blum, Department of Immunology, Nestlé Research Centre, Vers-Chez-les-Blanc, Ch-1000 Lausanne 26, Switzerland. Email: stephanie.blum-sperisen{at}rdls.nestle.com
  • Accepted 8 February 2000

Abstract

BACKGROUND AND AIM Intestinal epithelial cells (IEC) are thought to participate in the mucosal defence against bacteria and in the regulation of mucosal tissue homeostasis. Reactivity of IEC to bacterial signals may depend on interactions with immunocompetent cells. To address the question of whether non-pathogenic bacteria modify the immune response of the intestinal epithelium, we co-cultivated enterocyte-like CaCO-2 cells with human blood leucocytes in separate compartments of transwell cultures.

METHODS CaCO-2/PBMC co-cultures were stimulated with non-pathogenic bacteria and enteropathogenic Escherichia coli. Expression of tumour necrosis factor alpha (TNF-α), interleukin (IL)-1β, IL-8, monocyte chemoattracting protein 1 (MCP-1), and IL-10 was studied by enzyme linked immunosorbent assays (cytokine secretion) and by semiquantitative reverse transcription-polymerase chain reaction.

RESULTS Challenge of CaCO-2 cells with non-pathogenic E coli andLactobacillus sakei induced expression of IL-8, MCP-1, IL-1β, and TNF-α mRNA in the presence of underlying leucocytes. Leucocyte sensitised CaCO-2 cells produced TNF-α and IL-1β whereas IL-10 was exclusively secreted by human peripheral blood mononuclear cells. CaCO-2 cells alone remained hyporesponsive to the bacterial challenge. Lactobacillus johnsonii, an intestinal isolate, showed reduced potential to induce proinflammatory cytokines but increased transforming growth factor beta mRΝA in leucocyte sensitised CaCO-2 cells. TNF-α was identified as one of the early mediators involved in cellular cross talk. In the presence of leucocytes, discriminative activation of CaCO-2 cells was observed between enteropathogenicE coli and non-pathogenic bacteria.

CONCLUSION The differential recognition of non-pathogenic bacteria by CaCO-2 cells required the presence of underlying leucocytes. These results strengthen the hypothesis that bacterial signalling at the mucosal surface is dependent on a network of cellular interactions.

Footnotes

  • Abbreviations used in this paper:
    IEC
    intestinal epithelial cells
    PBMC
    peripheral blood mononuclear cells
    TNF-α
    tumour necrosis factor alpha
    IL-1β
    interleukin 1 beta
    IEL
    intraepithelial lymphocytes
    PBL
    peripheral blood lymphocytes
    LPL
    lamina propria lymphocytes
    RT-PCR
    reverse transcription-polymerase chain reaction
    TGF-β
    transforming growth factor beta
    PBS
    phosphate buffered saline
    TEER
    transepithelial electrical resistance
    LPS
    lipopolysaccharide
    bp
    base pair
    cfu
    colony forming units
    MCP-1
    monocyte chemoattracting protein 1
    mAb
    monoclonal antibody
    IBD
    inflammatory bowel disease