Sofia Östman

Impaired regulatory T cell function in germ-free mice

Regulatory T cells (Treg) are crucial for the maintenance of tolerance to auto‐antigens and harmless exogenous antigens. Here, we studied the role of the commensal microbiota for the development and function of Treg. CD4+CD25+ T cells were obtained from peripheral lymph nodes (PLN) and mesenteric lymph nodes (MLN) of germ‐free (GF) and conventional (conv) NMRI mice and tested for phenotype and functional suppressive capacity. CD4+CD25+ T cells from GF mice showed a lower relative gene expression of fork head box p3 gene (Foxp3) and were not as potent suppressors in vitro as CD4+CD25+ T cells from conv animals. Intracellular staining for Foxp3 and CTLA‐4 revealed proportional and regional differences in putative Treg subsets between conv and GF mice. Fewer of the CD4+CD25+ T cells in GF MLN expressed Foxp3 and CTLA‐4, while the expression of these markers was similar amongst the CD4+CD25+ T cells in PLN of conv and GF mice. The largest difference between conv and GF Treg was observed in the liver draining celiac lymph node, where GF mice had fewer putative Treg as compared to conv mice. We propose that the presence of a microbial flora favors the development of a fully functional Treg population.

Tolerosome-induced oral tolerance is MHC dependent

Oral administration of a protein antigen generates a serum factor that induces tolerance when transferred into naïve recipients. This serum factor has been described in rats as consisting of exosome‐like structures or tolerosomes, which express major histocompatibility complex class II molecules (MHCII) and mediate antigen‐specific tolerance. In this study, we investigated the functions of serum‐derived tolerosomes both in vivo and in vitro. Tolerosomes were purified from the 100 000 g pellet fraction of serum from ovalbumin (OVA)‐fed mice. When transferred into naïve recipient mice, the tolerosomes mediated OVA‐specific tolerance. We also found that tolerosomes from OVA‐fed mice induced the activation of OVA‐specific T cells both in vivo and in vitro. The inoculation of severe combined immunodeficiency (SCID) mice with an interferon‐γ‐producing cell line normalized the expression of MHCII in the intestinal epithelial cells and restored their ability to generate tolerosomes. Syngeneic but not allogeneic transfer of tolerosomes from OVA‐fed donors induced tolerance in the recipients. Our results show that tolerosomes can be isolated from mouse serum, that tolerosome‐induced oral tolerance requires MHCII expression in intestinal epithelial cells, and that tolerosomes are functional only in syngeneic recipients.

Induction of antigen-specific regulatory T cells in the liver-draining celiac lymph node following oral antigen administration

Regulatory T cells are induced by oral administration of an antigen, but the physiological requirements and localization of the inductive sites are largely unknown. Using an adoptive transfer system of cells transgenic for ovalbumin T‐cell receptor (OVA TCR tg), we found that antigen‐specific CD4+ T cells were activated in the liver‐draining celiac lymph node (CLN) shortly after ovalbumin feeding, and that a significantly higher proportion of the T cells in the CLN developed into the putative regulatory phenotype [co‐expressing CD25 with the glucocortico‐induced tumour necrosis factor (TNF) receptor family related gene (GITR), cytotoxic T‐lymphocyte antigen (CTLA)‐4 and CD103] than in Peyers patches, the mesenteric and peripheral lymph nodes and the spleen. In addition, a particularly high level of expression of CD103 on the OVA‐specific T cells in the CLN may favour homing to the epithelium of the intestine. While equally suppressive, OVA tg T cells isolated from the CLN of OVA‐fed DO11·10 mice were less dependent on transforming growth factor (TGF)‐β for suppression than cells isolated from the peripheral and mesenteric lymph nodes, which indicates the involvement of an additional suppressive mechanism. The expression of FoxP3 was not up‐regulated in any of the lymph node compartments studied. Our phenotypic and functional findings suggest that the induction of regulatory T cells in the CLN may be relevant in the control of the immune response to dietary antigens.

Neonatal exposure to staphylococcal superantigen improves induction of oral tolerance in a mouse model of airway allergy

The hygiene hypothesis suggests that lack of microbial stimulation in early infancy may lead to allergy, but it has been difficult to identify particular protective microbial exposures. We have observed that infants colonised in the first week(s) of life with Staphylococcus aureus have lower risk of developing food allergy. As many S. aureus strains produce superantigens with T‐cell stimulating properties, we here investigate whether neonatal mucosal exposure to superantigen could influence the capacity to develop oral tolerance and reduce sensitisation and allergy. BALB/c mice were exposed to staphylococcal enterotoxin A (SEA) as neonates and fed with OVA as adults, prior to sensitisation and i.n. OVA challenge. Our results show that SEA pre‐treated mice are more efficiently tolerised by OVA feeding, as shown by lower lung‐cell infiltration and antigen‐specific IgE response in the SEA pre‐treated mice, compared with sham‐treated mice. This was not due to deletion or anergy of lymphocytes by SEA treatment, because the SEA pre‐treated mice that were fed with PBS showed similar inflammatory response as the sham‐treated PBS‐fed mice. Our results suggest that strong T‐cell activation in infancy conditions the mucosal immune system and promotes development of oral tolerance.

Long-chain polyunsaturated fatty acids are consumed during allergic inflammation and affect T helper type 1 (Th1)- and Th2-mediated hypersensitivity differently

Studies have shown that atopic individuals have decreased serum levels of n‐3 fatty acids. Indicating these compounds may have a protective effect against allergic reaction and/or are consumed during inflammation. This study investigated whether fish (n‐3) or sunflower (n‐6) oil supplementation affected T helper type 1 (Th1)‐ and Th2‐mediated hypersensitivity in the skin and airways, respectively, and whether the fatty acid serum profile changed during the inflammatory response. Mice were fed regular chow, chow + 10% fish oil or chow + 10% sunflower oil. Mice were immunized with ovalbumin (OVA) resolved in Th1 or Th2 adjuvant. For Th1 hypersensitivity, mice were challenged with OVA in the footpad. Footpad swelling, OVA‐induced lymphocyte proliferation and cytokine production in the draining lymph node were evaluated. In the airway hypersensitivity model (Th2), mice were challenged intranasally with OVA and the resulting serum immunoglobulin (Ig)E and eosinophilic lung infiltration were measured. In the Th1 model, OVA‐specific T cells proliferated less and produced less interferon (IFN)‐γ, tumour necrosis factor (TNF) and interleukin (IL)‐6 in fish oil‐fed mice versus controls. Footpad swelling was reduced marginally. In contrast, mice fed fish oil in the Th2 model produced more OVA‐specific IgE and had slightly higher proportions of eosinophils in lung infiltrate. A significant fall in serum levels of long‐chain n‐3 fatty acids accompanied challenge and Th2‐mediated inflammation in Th2 model. Fish oil supplementation affects Th1 and Th2 immune responses conversely; significant consumption of n‐3 fatty acids occurs during Th2‐driven inflammation. The latter observation may explain the association between Th2‐mediated inflammation and low serum levels of n‐3 fatty acids.

Neonatal Mucosal Immune Stimulation by Microbial Superantigen Improves the Tolerogenic Capacity of CD103+ Dendritic Cells

Food allergy represents failure to develop tolerance to dietary proteins. Food allergy has increased in prevalence in parallel with decreased exposure to microbes during infancy. In mice, neonatal peroral exposure to the strongly T cell stimulating superantigen staphylococcal enterotoxin A (SEA), enhances the capacity to develop oral tolerance to a novel antigen encountered in adult life. A population of antigen-presenting cells in the gut, the CD103+ dendritic cells (DCs), is thought to be involved in oral tolerance development, as they convert naïve T cells into FoxP3+ regulatory T cells (Treg). This function depends on their capacity to convert vitamin A to retinoic acid, carried out by the retinal aldehyde dehydrogenase (RALDH) enzyme. Here, newborn mice were treated with superantigen and DC function and tolerogenic capacity was examined at six weeks of age. We observed that, in mice fed superantigen neonatally, the CD11c+ DCs had increased expression of RALDH and in vitro more efficiently induced expression Foxp3 expression to stimulated T cells. Further, these mice showed an accumulation of FoxP3+ T cells in the small intestinal lamina propria and had a more Ag-specific FoxP3+ T cells after oral tolerance induction in vivo. Moreover, the improved oral tolerance, as shown by increased protection from food allergy, was eradicated if the Vitamin A metabolism was inhibited. These observations contribute to the understanding of how a strong immune stimulation during the neonatal period influences the maturation of the immune system and suggests that such stimulation may reduce the risk of later allergy development.

The oral microbiota of patients with recurrent aphthous stomatitis

Background Specific pathogenic bacteria have been implicated in recurrent aphthous stomatitis (RAS), a chronic inflammatory condition characterised by ulcerations in the oral mucosa. However, the aetiology behind this condition still remains unclear. Objective The buccal microbiota of patients with RAS was compared to that of control subjects to investigate its potential role for this condition. Design Buccal swabs were obtained from non-ulcerative areas of 60 patients, of whom 42 patients had lesions at the time of sampling, and 60 healthy age- and gender-matched controls. Bacterial DNA was extracted and analysed by Terminal-Restriction Fragment Length Polymorphism, using enzymatic digestion of the polymerase chain reaction-amplified 16S rRNA gene, yielding a series of peaks, each representing a bacterial taxon. Results Two peaks, 60 and 489, were more prevalent in patients with RAS than controls. Conversely, peaks 58 and 490 were less common in patients than controls. When the patients were divided into subgroups, we found that the observed differences in peak-pattern were related to the presence of lesions during sampling. Conclusions The microbiota of the non-inflamed buccal mucosa differed between patients and controls. The differences were most pronounced in patients who presented with lesions during sampling, suggesting that a disturbance in the normal buccal microbiota triggers the presence of lesions or that presence of lesions alters the microbiota.

Identification of gliadin-binding peptides by phage display

BackgroundCoeliac disease (CD) is a common and complex disorder of the small intestine caused by intolerance to wheat gluten and related edible cereals like barley and rye. Peptides originating from incomplete gliadin digestion activate the lamina propria infiltrating T cells to release proinflammatory cytokines, which in turn cause profound tissue remodelling of the small intestinal wall. There is no cure for CD except refraining from consuming gluten-containing products.ResultsPhage from a random oligomer display library were enriched by repeated pannings against immobilised gliadin proteins. Phage from the final panning round were plated, individual plaques picked, incubated with host bacteria, amplified to a population size of 1011 to 1012 and purified. DNA was isolated from 1000 purified phage populations and the region covering the 36 bp oligonucleotide insert from which the displayed peptides were translated, was sequenced. Altogether more than 150 different peptide-encoding sequences were identified, many of which were repeatedly isolated under various experimental conditions. Amplified phage populations, each expressing a single peptide, were tested first in pools and then one by one for their ability to inhibit binding of human anti-gliadin antibodies in ELISA assays. These experiments showed that several of the different peptide-expressing phage tested inhibited the interaction between gliadin and anti-gliadin antibodies. Finally, four different peptide-encoding sequences were selected for further analysis, and the corresponding 12-mer peptides were synthesised in vitro. By ELISA assays it was demonstrated that several of the peptides inhibited the interaction between gliadin molecules and serum anti-gliadin antibodies. Moreover, ELISA competition experiments as well as dot-blot and western blot revealed that the different peptides interacted with different molecular sites of gliadin.ConclusionsWe believe that several of the isolated and characterised gliadin-binding peptides described here could provide valuable tools for researchers in the field of CD by facilitating studies on localisation and uptake of various gliadin peptides in the small intestine. In future work, the potential of these peptides to detoxify gluten will be investigated.

Does Crohn's Disease with Concomitant Orofacial Granulomatosis Represent a Distinctive Disease Subtype?

Background:Although orofacial granulomatosis (OFG) may present as a separate clinical entity, it often seems in conjunction with various systemic diseases, of which Crohns disease (CD) is one of the most common. The aim of this study was to investigate whether CD with concomitant OFG represents a distinctive disease subtype. Methods:Twenty-one patients with CD and concomitant OFG (CD+OFG group) were included in the study. As the reference group, a cohort of 39 patients with CD but without OFG (CD-R group) was used. Demographic data and clinical characteristics were recorded at the time of diagnosis. The 2 groups were compared using multivariate analyses. Results:The percentage of patients with intestinal inflammation in the upper gastrointestinal tract was significantly higher in the CD+OFG group, as compared with the CD-R group (81% versus 33%; P < 0.001). Furthermore, ileocolonic inflammation was significantly more common in the CD+OFG patients (81% versus 46%; P = 0.013). In addition, perianal disease was more frequently observed in the CD+OFG group (48% versus 18%; P = 0.033). Significantly more patients showed evidence of granulomas in the primary endoscopy in the CD+OFG group than in the CD-R group (81% versus 38%; P = 0.003). Conclusion:The data from this study suggest that the presence of CD in conjunction with OFG represents a distinctive subphenotype of CD that is characterized by extensive inflammation, perianal disease, and pronounced granuloma formation in the intestine.

The Polyunsaturated Fatty Acids Arachidonic Acid and Docosahexaenoic Acid Induce Mouse Dendritic Cells Maturation but Reduce T-Cell Responses In Vitro

Long-chain polyunsaturated fatty acids (PUFAs) might regulate T-cell activation and lineage commitment. Here, we measured the effects of omega-3 (n-3), n-6 and n-9 fatty acids on the interaction between dendritic cells (DCs) and naïve T cells. Spleen DCs from BALB/c mice were cultured in vitro with ovalbumin (OVA) with 50 μM fatty acids; α-linolenic acid, arachidonic acid (AA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), linoleic acid or oleic acid and thereafter OVA-specific DO11.10 T cells were added to the cultures. Fatty acids were taken up by the DCs, as shown by gas chromatography analysis. After culture with arachidonic acid or DHA CD11c+ CD11b+ and CD11c+ CD11bneg DCs expressed more CD40, CD80, CD83, CD86 and PDL-1, while IAd remained unchanged. However, fewer T cells co-cultured with these DCs proliferated (CellTrace Violetlow) and expressed CD69 or CD25, while more were necrotic (7AAD+). We noted an increased proportion of T cells with a regulatory T cell (Treg) phenotype, i.e., when gating on CD4+ FoxP3+ CTLA-4+, CD4+ FoxP3+ Helios+ or CD4+ FoxP3+ PD-1+, in co-cultures with arachidonic acid- or DHA-primed DCs relative to control cultures. The proportion of putative Tregs was inversely correlated to T-cell proliferation, indicating a suppressive function of these cells. With arachidonic acid DCs produced higher levels of prostaglandin E2 while T cells produced lower amounts of IL-10 and IFNγ. In conclusion arachidonic acid and DHA induced up-regulation of activation markers on DCs. However arachidonic acid- and DHA-primed DCs reduced T-cell proliferation and increased the proportion of T cells expressing FoxP3, indicating that these fatty acids can promote induction of regulatory T cells.