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

Inflammation and inflammatory bowel disease

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

D Hallera,b,
C Bodea,
W P Hammesb,
A M A Pfeiferc,
E J Schiffrinc,
S Blumc
aInstitute of Biological Chemistry and Nutrition Science, University Hohenheim, Germany, bInstitute of Food Technology, University Hohenheim, Germany, cImmunology, Nestlé Research Centre, Lausanne, Switzerland
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

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 and_Lactobacillus 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 enteropathogenic_E 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.

CaCO-2 cells
leucocytes
enteropathogenic_E coli_
Lactobacilli
tumour necrosis factor
interleukin 1β
interleukin 10
chemokines
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

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