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Karger Publishers, International Archives of Allergy and Immunology, 2(152), p. 159-168, 2009

DOI: 10.1159/000265537

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Exposure of Intestinal Epithelial Cells to UV-Killed Lactobacillus GG but Not Bifidobacterium breve Enhances the Effector Immune Response in vitro

This paper is available in a repository.
This paper is available in a repository.

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Abstract

<i>Background:</i> Intestinal bacteria and intestinal epithelial cells (IEC) may modulate the mucosal immune response. In this study, immune modulation by <i>Lactobacillus GG (LGG)</i> and <i>Bifidobacterium breve (Bb1, Bb2)</i> in the presence or absence of IEC was addressed in an in vitro transwell co-culture model. <i>Methods:</i> UV-killed <i>LGG,</i><i>Bb1, Bb2 </i>or Toll-like receptor (TLR) 2 or nucleotide oligomerization domain (NOD) 2 ligands were added directly to unstimulated or anti-CD3/CD28-stimulated PBMC, or applied apically to human IEC (HT-29) co-cultured with PBMC. A mixture of live bacteria was used as reference. The effect on T helper 1 (IFN-γ, IL-12), T helper 2 (IL-13), inflammatory (TNF-α) and regulatory (IL-10) cytokine secretion was determined. <i>Results:</i> Both UV-killed <i>LGG</i> and <i>Bb</i> enhanced IL-12, IFN-γ, TNF-α and IL-10, and reduced IL-13 secretion when added directly to stimulated PBMC, similar to live bacteria. IEC reduced IL-13, IFN-γ and IL-10 secretion by stimulated PBMC. Apically added <i>LGG, </i>TLR2 and NOD2 ligands,but not<i> Bb</i>, enhanced IFN-γ, IL-12 and/or TNF-α secretion. Bacteria did not induce cytokine secretion when added to HT-29/unstimulated PBMC co-cultures, whereas direct incubations with PBMC did. <i>Conclusion:</i> UV-killed <i>LGG</i> as well as <i>Bb</i> supported a T helper 1 and/or regulatory phenotype when added directly to activated PBMC, similar to live bacteria. In contrast, <i>LGG</i>, TLR2 or NOD2 ligands – but not <i>Bb</i> – enhanced T helper 1 type cytokine secretion when added to IEC, while IL-10 secretion remained suppressed. Co-cultures combining IEC and PBMC may reveal differences between bacterial strains relevant for the in vivo situation.