ABSTRACT: Dendritic cells (DC) dictate not only the type of T-cell immunity, but also homing patterns of T cells in mice. In humans, we characterized normal human gut DC and tested whether gut-specific homeostatic DC could be generated from blood precursors by factors in the gut microenvironment.
We characterized the phenotype and function of healthy human gut DC compared with blood and skin DC, and studied whether conditioning of blood DC in the presence of colonic biopsy supernatants (Bx-SN) induced gut-like phenotype and functions.
Blood DC mostly expressed both gut and skin homing markers, indicating potential to migrate to both major immune surface organs, and induced multi-homing T cells. However, DC within gut or skin did not demonstrate this multi-homing phenotype, were tissue-specific, and induced tissue-specific T cells. Human gut DC were less stimulatory for allogeneic T cells than their dermal and blood counterparts. Human blood DC cultured in vitro lost homing marker expression. Conditioning of human enriched blood DC with colonic Bx-SN from healthy controls induced a gut-homing phenotype and a homeostatic profile. Moreover, Bx-SN-conditioned DC demonstrated a restricted T-cell stimulatory capacity and preferentially induced gut-specific T cells. Retinoic acid and transforming growth factor beta (TGF-β) mediated the acquisition of the gut-homing and homeostatic properties, respectively, induced by colonic Bx-SN on blood enriched DC.
Tissue-specific factors manipulate immunity via modulating characteristics of DC and may provide tools to generate tissue-specific immunotherapy.
Inflammatory Bowel Diseases 10/2011; 18(7):1275-86. · 4.86 Impact Factor
ABSTRACT: Patients with Crohn's disease (CD) have an intestinal dysbiosis with components of the microbiota exerting differential immune effects. Smoking is associated with an increased incidence of CD, more frequent relapse, and greater burden of surgery. This study aimed to investigate the association between smoking and the intestinal microbiota in patients with active CD.
Patients with active CD (n = 103) and healthy controls (n = 66) were recruited and demographic and clinical data recorded including current smoking behavior. Fecal samples were collected and analyzed by fluorescent in situ hybridization using probes targeting 16S rRNA of bacteria previously shown to be altered in active CD (bifidobacteria, bacteroides, Clostridium coccoides-Eubacterium rectale, Escherichia coli, and Faecalibacterium prausnitzii).
In total, 29/101 (29%) patients with CD and 8/58 (14%) controls were current smokers (P = 0.032). Following multivariate analysis, smoking was found to have a significant and independent effect on the microbiota of patients with CD, with higher Bacteroides-Prevotella in smokers (38.4%) compared with nonsmokers (28.1%) (F((1,93)) = 12.6, P = 0.001). Healthy controls who smoked also had higher Bacteroides-Prevotella (34.8%) than nonsmokers (24.1%) (F((1,55)) = 4.5, P = 0.038). In the pooled multivariate analysis, patients with CD had higher bifidobacteria (F((1,156)) = 30.5, P < 0.001), higher Bacteroides-Prevotella (F((1,156)) = 6.5, P = 0.012), and lower F. prausnitzii (F((1,156)) = 3.8, P = 0.052) compared with healthy controls.
Smokers have luminal microbiota that consist of significantly higher bacteroides. Investigation of whether this is one mechanism through which the negative effects of smoking on CD are mediated is warranted.
Inflammatory Bowel Diseases 08/2011; 18(6):1092-100. · 4.86 Impact Factor
ABSTRACT: The commensal intestinal microbiota drive the inflammation associated with Crohn's disease. However, bacteria such as bifidobacteria and Faecalibacterium prausnitzii appear to be immunoregulatory. In healthy subjects the intestinal microbiota are influenced by prebiotic carbohydrates such as fructo-oligosaccharides (FOS). Preliminary data suggest that FOS increase faecal bifidobacteria, induce immunoregulatory dendritic cell (DC) responses and reduce disease activity in patients with Crohn's disease.
To assess the impact of FOS in patients with active Crohn's disease using an adequately powered randomised double-blind placebo-controlled trial with predefined clinical, microbiological and immunological end points. Patients with active Crohn's disease were randomised to 15 g/day FOS or non-prebiotic placebo for 4 weeks. The primary end point was clinical response at week 4 (fall in Crohn's Disease Activity Index of ≥ 70 points) in the intention-to-treat (ITT) population.
103 patients were randomised to receive FOS (n = 54) or placebo (n = 49). More patients receiving FOS (14 (26%) vs 4 (8%); p = 0.018) withdrew before the 4-week end point. There was no significant difference in the number of patients achieving a clinical response between the FOS and placebo groups in the ITT analysis (12 (22%) vs 19 (39%), p = 0.067). Patients receiving FOS had reduced proportions of interleukin (IL)-6-positive lamina propria DC and increased DC staining of IL-10 (p < 0.05) but no change in IL-12p40 production. There were no significant differences in the faecal concentration of bifidobacteria and F prausnitzii between the groups at baseline or after the 4-week intervention.
An adequately powered placebo-controlled trial of FOS showed no clinical benefit in patients with active Crohn's disease, despite impacting on DC function. ISRCTN50422530.
Gut 01/2011; 60(7):923-9. · 10.11 Impact Factor