Comparison of the immunomodulatory properties of three probiotic strains of Lactobacilli using complex culture systems: prediction for in vivo efficacy

Background: While the use of probiotics to treat or prevent inflammatory bowel disease (IBD) has been proposed, to this point the clinical benefits have been limited. In this report we analyzed the immunological activity of three strains of Lactobacillus to predict their in vivo efficacy in protecting against experimental colitis. Methodology/Principal Findings: We compared the immunological properties of Lactobacillus plantarum NCIMB8826, L. rhamnosus GG (LGG), L. paracasei B21060 and pathogenic Salmonella typhimurium (SL1344). We studied the stimulatory effects of these different strains upon dendritic cells (DCs) either directly by co-culture or indirectly via conditioning of an epithelial intermediary. Furthermore, we characterized the effects of these strains in vivo using a Dextran sulphate sodium (DSS) model of colitis. We found that the three strains exhibited different abilities to induce inflammatory cytokine production by DCs with L. plantarum being the most effective followed by LGG and L. paracasei. L. paracasei minimally induced the release of cytokines, while it also inhibited the potential of DCs to both produce inflammatory cytokines (IL-12 and TNF-\u3b1) and to drive Th1 T cells in response to Salmonella. This effect on DCs was found under both direct and indirect stimulatory conditions - i.e. mediated by epithelial cells - and was dependent upon an as yet unidentified soluble mediator. When tested in vivo, L. plantarum and LGG exacerbated the development of DSS-induced colitis and caused the death of treated mice, while, conversely L. paracasei was protective. Conclusions: We describe a new property of probiotics to either directly or indirectly inhibit DC activation by inflammatory bacteria. Moreover, some immunostimulatory probiotics not only failed to protect against colitis, they actually amplified the disease progression. In conclusion, caution must be exercised when choosing a probiotic strain to treat IBD

The yin and yang of intestinal epithelial cells in controlling dendritic cell function

Recent work suggests that dendritic cells (DCs) in mucosal tissues are "educated" by intestinal epithelial cells (IECs) to suppress inflammation and promote immunological tolerance. After attack by pathogenic microorganisms, however, "non-educated" DCs are recruited from nearby areas, such as the dome of Peyer's patches (PPs) and the blood, to initiate inflammation and the ensuing immune response to the invader. Differential epithelial cell (EC) responses to commensals and pathogens may control these two tolorogenic and immunogenic functions of DCs. JE

Intestinal epithelial cells promote colitis-protective regulatory T-cell differentiation through dendritic cell conditioning

Intestinal dendritic cells (DCs) have been shown to display specialized functions, including the ability to promote gut tropism to lymphocytes, to polarize noninflammatory responses, and to drive the differentiation of adaptive Foxp3+ regulatory T (Treg) cells. However, very little is known about what drives the mucosal phenotype of DCs. Here, we present evidence that the local microenvironment, and in particular intestinal epithelial cells (ECs), drive the differentiation of Treg-cell-promoting DCs, which counteracts Th1 and Th17 development. EC-derived transforming growth factor-\u3b2 (TGF-\u3b2) and retinoic acid (RA), but not thymic stromal lymphopoietin (TSLP), were found to be required for DC conversion. After EC contact, DCs upregulated CD103 and acquired a tolerogenic phenotype. EC-conditioned DCs were capable of inducing de novo Treg cells with gut-homing properties that when adoptively transferred, protected mice from experimental colitis. Thus, we have uncovered an essential mechanism in which EC control of DC function is required for tolerance induction

Recursion operators and hierarchies of mKdV\text{mKdV} equations related to the Kac–Moody algebras D4(1)D_4^{(1)}, D4(2)D_4^{(2)}, and D4(3)D_4^{(3)}

International audienceWe construct three nonequivalent gradings in the algebra $D_4\simeq so(8)$. The first is the standard grading obtained with the Coxeter automorphism $C_1=S_{\alpha_2}S_{\alpha_1}S_{\alpha_3}S_{\alpha_4}$ using its dihedral realization. In the second, we use $C_2=C_1R$, where $R$ is the mirror automorphism. The third is $C_3=S_{\alpha_2}S_{\alpha_1}T$, where $T$ is the external automorphism of order 3. For each of these gradings, we construct a basis in the corresponding linear subspaces $\mathfrak{g}^{(k)}$, the orbits of the Coxeter automorphisms, and the related Lax pairs generating the corresponding modified Korteweg–de Vries (mKdV) hierarchies. We find compact expressions for each of the hierarchies in terms of recursion operators. Finally, we write the first nontrivial mKdV equations and their Hamiltonians in explicit form. For $D_4^{(1)}$, these are in fact two mKdV systems because the exponent 3 has the multiplicity two in this case. Each of these mKdV systems consists of four equations of third order in $\partial_x$. For $D_4^{(2)}$, we have a system of three equations of third order in $\partial_x$. For $D_4^{(3)}$, we have a system of two equations of fifth order in $\partial_x$

Gut CD103+ dendritic cells express indoleamine 2,3-dioxygenase which influences T regulatory/T effector cell balance and oral tolerance induction

Objective: CD103+ gut dendritic cells (DCs) have been shown to be required for de novo conversion of adaptive T regulatory (Treg) cells. Indoleamine 2,3-dioxygenase (IDO) is an enzyme involved in tryptophan catabolism that is expressed by DCs isolated from tumour-draining lymph nodes. IDO-expressing DCs sustain and differentiate Tregs. The aim of this study was to investigate the expression and the possible physiological role of IDO in the tolerogenic properties of intestinal DCs. Design: The expression level of IDO in CD103+ and CD103- DCs was analysed by qRT-PCR, western blot and immunofluorescence. CD103+ and CD103- DCs were sorted from mesenteric lymph nodes (MLNs) and the small intestinal lamina propria, and the role of IDO in the conversion of Tregs and Th effector cell development was evaluated via specific inhibition or gene deletion. Oral tolerance, experimental colitis and T cell differentiation in vivo were assessed upon IDO inactivation. Results: We show that, primarily, CD103+ but not CD103- gut DCs express IDO whose inhibition results in reduced CD4+Foxp3+ T regulatory cell conversion and enhanced T cell proliferation. When IDO was inhibited or genetically deleted there was an increase in Th1 and Th17 differentiation both in vitro and in vivo. Finally, in vivo IDO blockade affected the development of Tregs specific for orally administered antigens, impaired oral tolerance induction and exacerbated colitis. Conclusions: We identified a new IDO-dependent pathway leading to acquisition of tolerogenic functions in mucosal CD103-expressing DCs, indicating IDO as a possible therapeutic target for gut disorders

Human intestinal epithelial cells promote the differentiation of tolerogenic dendritic cells

Objective: In mice, a subpopulation of gut dendritic cells (DCs) expressing CD103 drives the development of regulatory T (Treg) cells. Further, it was recently described that the cross-talk between human intestinal epithelial cells (IECs) and DCs helps in maintaining gut immune homeostasis via the induction of non-inflammatory DCs. In this study, an analysis was carried out to determine whether IECs could promote the differentiation of CD103 + tolerogenic DCs, and the function of primary CD103+ DCs isolated from human mesenteric lymph nodes (MLNs) was evaluated. Methods: Monocyte-derived DCs (MoDCs) and circulating CD1c+ DCs were conditioned or not with supernatants from Caco-2 cells or IECs isolated from healthy donors or donors with Crohn's disease and analysed for their ability to induce Treg cell differentiation. In some cases, transforming growth factor \u3b2 (TGFb), retinoic acid (RA) or thymic stromal lymphopoietin (TSLP) were neutralised before conditioning. CD103+ and CD1032 DCs were sorted by fluorescence-activated cell sorting (FACS) from MLNs and used in Treg cell differentiation experiments. Results: It was found that human IECs promoted the differentiation of tolerogenic DCs able to drive the development of adaptive Foxp3+ Treg cells. This control was lost in patients with Crohn's disease and paralleled a reduced expression of tolerogenic factors by primary IECs. MoDCs differentiated with RA or IEC supernatant upregulated the expression of CD103. Consistently, human primary CD103+ DCs isolated from MLNs were endowed with the ability to drive Treg cell differentiation. This subset of DCs expressed CCR7 and probably represents a lamina propria-derived migratory population. Conclusions: A population of tolerogenic CD103+ DCs was identified in the human gut that probably differentiate in response to IEC-derived factors and drive Treg cell development