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- Sjöberg, Veronika, 1980-
(author)
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Immune response of the small intestinal mucosa in children with celiac disease : impact of two environmental factors, resident microbiota and oats
- 2013
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Doctoral thesis (other academic/artistic)abstract
- Celiac disease (CD) is an immune-mediated enteropathy caused by permanent intolerance to dietary gliadin in wheat gluten and related prolamines in barley and rye. The pathogenesis of CD is still unknown and several different environmental factors have been associated with CD, such as dysbiosis of the microflora. In this translational study we investigated the immune status and the interplay of T-cells and Tregs in the mucosa of children with CD and controls, as well as the immune status in treated CD patients, provoked by either dietary oats, CD associated bacteria or gluten.The major findings in the studies were: First, indicators of extrathymic T-cells maturation (ETCM), i.e., the RAG1 enzyme required for recombination of the T cell receptor (TCR) genes and the preTα-surrogate chain in the immature TCR, were both expressed at lower levels in CD patients compared to controls. In addition, IELs expressing RAG1 were less abundant in CD patients compared to controls. The levels of these two indicators stayed low in treated CD patients as well, suggesting that impaired capacity of ETCM is an inherent feature of CD patients. Second, IL-17A, a cytokine involved in both inflammation and anti-bacterial responses was increased in active CD. The major cellular source was CD8+IELs. Furthermore, ex vivo challenge of biopsies from treated CD patients with gluten and with CD-associated bacteria induced an IL-17A response. The CD-associated bacteria also influenced the magnitude of the IL-17A response to gluten. Third, we investigated the effect of dietary oats on local immune status in the intestinal mucosa by comparing CD patients receiving GFD with and without oats. 22 different mRNAs for immunity effector molecules and tight junction proteins were analyzed. We found that expression of two down-regulatory cytokines, two activating NK-receptors and the tight-junction protein claudin-4 normalized in patients on a standard GFD while they did not normalize in patients on a GFD with oats. Fourth, we analyzed the expression level of mRNAs for chemokines, cytotoxic effector molecules, NK-receptors and their ligands in IELs and epithelial cells. Expression levels of several of these genes follow disease activity, suggesting massive recruitment of immune cells by both cell types accompanied by increased IEL-mediated cytotoxicity in the epithelium of inflamed mucosa.In this thesis we have identified three potential risk factors for development of CD: 1) an inherent lower level of ETCM in the small intestinal mucosa than in controls. This could lead to decreased generation of regulatory T cells and less capacity to tolerate gluten and adapt to the local milieu in the mucosa. 2) Dysbiosis of the resident microbiota with increased IL-17A production that could promote local inflammation and immune cell infiltration as well as antibacterial reactions. 3) Dietary oats may provoke a local immune response in a sub-population of CD patients. These patients should probably avoid oats in their GFD but larger studies are needed.
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| 2. |
- West, Christina, 1969-
(author)
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Feeding Lactobacillus paracasei ssp. paracasei strain F19 to infants during weaning : effects on adaptive immunity and gut microbial function
- 2008
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Doctoral thesis (other academic/artistic)abstract
- Introduction: Gut microbial composition has been associated with immune-mediated diseases. Breastfeeding yields a microbiota rich in bifidobacteria and promotes colonization by lactobacilli. Bifidobacteria and lactobacilli are considered health-promoting and are used as probiotics, i.e. live microbial food supplements which when ingested in adequate amounts confer a beneficial effect on the host. During weaning the developing gut immune system is exposed to an increasing variety of antigens from both foods and gut microbiota.Aims: We aimed to determine if daily feeding of 1x108 colony-forming units (CFU) of the probiotic Lactobacillus paracasei ssp. paracasei strain F19 (LF19) to healthy term infants from 4 to 13 months of age could maintain some of the beneficial effects conferred by breastfeeding on gut microbial composition, with possible effects on gut microbial function, T cell function, Th1/Th2 immune balance and eczema incidence.Study design: Infants were randomized to daily intake of cereals with (n=89) or without LF19 (n=90) from 4-13 months of age. Clinical outcome measures were monitored by diaries and a questionnaire. Stool and blood samples were obtained at 4, 6½, 9, 13 and 5½, 6½, 12 and 13 months of age, respectively. Stool samples were analyzed for lactobacilli counts by conventional culture methods and the presence of LF19 was verified by randomly amplified polymerase chain reaction (RAPD-PCR). Fecal short-chain fatty acid (SCFA) pattern, a proxy for gut microbial function, was determined by gas-liquid chromatography. After polyclonal or specific activation of T cells, the cytokine mRNA expression levels [interleukin 2 (IL2), IFN-, IL4 and IL10] were determined on isolated mRNA by quantitative real time reverse transcriptase-PCR. Serum concentrations of total and specific IgE antibodies, Haemophilus influenzae type b, diphtheria and tetanus toxoid specific IgG antibodies were analyzed by enzyme immunoassay.Results: Feeding LF19 maintained high fecal lactobacilli counts during weaning. Persistent colonization with LF19 induced differences in the fecal SCFA pattern. The cumulative incidence of eczema was lower in the probiotic group, in conjunction with a higher IFN-γ/IL4 mRNA ratio in polyclonally activated T cells. Even though there was an effect by LF19 on Th1/Th2 immune balance, there was no effect on IgE sensitization. Infants in both groups increased their capacity to express both Th1 and Th2 cytokines during the second half of infancy but the expression was still lower than that of adults. Infants in the probiotic group had lower IL2 levels after polyclonal T cell activation at 13 months of age compared with infants in the placebo group. Infants fed LF19 did not have fewer infections, but had fewer days with antibiotic prescription compared with infants fed placebo. In addition, compared to placebo, persistent colonization by LF19 enhanced specific vaccine responses to protein antigens during the course of vaccination.Conclusions: We conclude that feeding LF19 was safe, based on no observed adverse effects in our study. Infants in both groups demonstrated maturation of adaptive immune responses during weaning. Adding probiotics in complementary foods during weaning reduced the risk of eczema by 50%, with a concomitant shift towards an enhanced Th1/Th2 ratio. The reduction of eczema might be explained by probiotic effects on both T cell-mediated immune responses and reinforced gut microbial function.
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