Exposure of intestinal epithelial cells to UV-killed Lactobacillus GG but not Bifidobacterium breve enhances the effector immune response in vitro.
BACKGROUND
Intestinal bacteria and intestinal epithelial cells (IEC) may modulate the mucosal immune response. In this study, immune modulation by Lactobacillus GG (LGG) and Bifidobacterium breve (Bb1, Bb2) in the presence or absence of IEC was addressed in an in vitro transwell co-culture model.


METHODS
UV-killed LGG,Bb1, Bb2 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-gamma, IL-12), T helper 2 (IL-13), inflammatory (TNF-alpha) and regulatory (IL-10) cytokine secretion was determined.


RESULTS
Both UV-killed LGG and Bb enhanced IL-12, IFN-gamma, TNF-alpha and IL-10, and reduced IL-13 secretion when added directly to stimulated PBMC, similar to live bacteria. IEC reduced IL-13, IFN-gamma and IL-10 secretion by stimulated PBMC. Apically added LGG, TLR2 and NOD2 ligands,but not Bb, enhanced IFN-gamma, IL-12 and/or TNF-alpha secretion. Bacteria did not induce cytokine secretion when added to HT-29/unstimulated PBMC co-cultures, whereas direct incubations with PBMC did.


CONCLUSIONS
UV-killed LGG as well as Bb supported a T helper 1 and/or regulatory phenotype when added directly to activated PBMC, similar to live bacteria. In contrast, LGG, TLR2 or NOD2 ligands - but not Bb - 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.
van Hoffen
Els
E
Dermatology/Allergology, University Medical Center Utrecht, Utrecht, The Netherlands.
Korthagen
Nicoline M
NM
de Kivit
Sander
S
Schouten
Bastiaan
B
Bardoel
Bart
B
Duivelshof
Arjan
A
Knol
Jan
J
Garssen
Johan
J
Willemsen
Linette E M
LE
D000119:Acetylmuramyl-Alanyl-Isoglutamine / Q000494:pharmacology; D000276:Adjuvants, Immunologic / Q000494:pharmacology; D000906:Antibodies / Q000276:immunology / Q000494:pharmacology; D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology; D001644:Bifidobacterium / Q000276:immunology* / Q000528:radiation effects; D049109:Cell Proliferation / Q000187:drug effects; D018920:Coculture Techniques; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D019073:HT29 Cells; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism; D007378:Interleukins / Q000378:metabolism; D007413:Intestinal Mucosa / Q000166:cytology* / Q000276:immunology; D007778:Lactobacillus / Q000276:immunology* / Q000528:radiation effects; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D055666:Lipopeptides / Q000494:pharmacology; D053473:Nod2 Signaling Adaptor Protein / Q000819:agonists; D019936:Probiotics / Q000494:pharmacology; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D051195:Toll-Like Receptor 2 / Q000819:agonists; D053773:Transforming Growth Factor beta1 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D014466:Ultraviolet Rays
D000276:Adjuvants, Immunologic; D000906:Antibodies; D000945:Antigens, Differentiation, T-Lymphocyte; D007378:Interleukins; D055666:Lipopeptides; C429018:NOD2 protein, human; D053473:Nod2 Signaling Adaptor Protein; C508075:Pam(3)CSK(4) peptide; C495342:TLR2 protein, human; D051195:Toll-Like Receptor 2; D053773:Transforming Growth Factor beta1; D014409:Tumor Necrosis Factor-alpha; D000119:Acetylmuramyl-Alanyl-Isoglutamine; D007371:Interferon-gamma