Nobuyasu Baba

Common variants in the NLRP3 region contribute to Crohn's disease susceptibility

We used a candidate gene approach to identify a set of SNPs, located in a predicted regulatory region on chromosome 1q44 downstream of NLRP3 (previously known as CIAS1 and NALP3) that are associated with Crohns disease. The associations were consistently replicated in four sample sets from individuals of European descent. In the combined analysis of all samples (710 father-mother-child trios, 239 cases and 107 controls), these SNPs were strongly associated with risk of Crohns disease (Pcombined = 3.49 × 10−9, odds ratio = 1.78, confidence interval = 1.47–2.16 for rs10733113), reaching a level consistent with the stringent significance thresholds imposed by whole-genome association studies. In addition, we observed significant associations between SNPs in the associated regions and NLRP3 expression and IL-1β production. Mutations in NLRP3 are known to be responsible for three rare autoinflammatory disorders. These results suggest that the NLRP3 region is also implicated in the susceptibility of more common inflammatory diseases such as Crohns disease.

Thrombospondin/CD47 Interaction: A Pathway to Generate Regulatory T Cells from Human CD4+CD25− T Cells in Response to Inflammation

Thymus-derived CD4+ CD25+ T regulatory cells (Tregs) are essential for the maintenance of self-tolerance. What critical factors and conditions are required for the extra-thymic development of Tregs remains an important question. In this study, we show that the anti-inflammatory extracellular matrix protein, thrombospondin-1, promoted the generation of human peripheral regulatory T cells through the ligation of one of its receptor, CD47. CD47 stimulation by mAb or a thrombospondin-1 peptide induced naive or memory CD4+CD25− T cells to become suppressive. The latter expressed increased amounts of CTLA-4, OX40, GITR, and Foxp3 and inhibited autologous Th0, Th1, and Th2 cells. Their regulatory activity was contact dependent, TGF-β independent, and partially circumvented by IL-2. This previously unknown mechanism to induce human peripheral Tregs in response to inflammation may participate to the limitation of collateral damage induced by exacerbated responses to self or foreign Ags and thus be relevant for therapeutic intervention in autoimmune diseases and transplantation.

Commensal bacteria trigger a full dendritic cell maturation program that promotes the expansion of non-Tr1 suppressor T cells

Dendritic cells (DCs) orchestrate the immune response establishing immunity versus tolerance. These two opposite functions may be dictated by DC maturation status with maturity linked to immunogenicity. DCs directly interact with trillions of noninvasive intestinal bacteria in vivo, a process that contributes to gut homeostasis. We here evaluated the maturation program elicited in human DCs by direct exposure to commensal‐related bacteria (CB) in the absence of inflammatory signals. We showed that eight gram+ and gram− CB strains up‐regulated costimulatory molecule expression in DCs and provoked a chemokine receptor switch similar to that activated by gram+ pathogens. CB strains may be classified into three groups according to DC cytokine release: high IL‐12 and low IL‐10; low IL‐12 and high IL‐10; and low IL‐12 and IL‐10. All CB‐treated DCs produced IL‐1β and IL‐6 and almost no TGF‐β. Yet, CB instructed DCs to convert naive CD4+ T cells into hyporesponsive T cells that secreted low or no IFN‐γ, IL‐10, and IL‐17 and instead, displayed suppressor function. These data demonstrate that phenotypic DC maturation combined to an appropriate cytokine profile is insufficient to warrant Th1, IL‐10‐secreting T regulatory Type 1 (Tr1), or Th17 polarization. We propose that commensal flora and as such, probiotics manipulate DCs by a yet‐unidentified pathway to enforce gut tolerance.

CD28 Co-Stimulation Down Regulates Th17 Development

Th17 cells are implicated in host defence and autoimmune diseases. CD28/B7 co-stimulation is involved in the induction and progression of autoimmune diseases, but its role in controlling murine Th17 cell fate remains to be clarified. We here report that soluble anti-CD28 mAb suppressed the differentiation of anti-CD3-stimulated naïve CD4+ T cells into IL-17-producing cells. CD28 co-stimulation reduced the frequency of proliferating cells that produce IL-17. We provide evidence for an IL-2 and IFN-γ-dependent mechanism of CD28-mediated IL-17 suppression. CD28 blockade of Th17 development was correlated with a decrease rather than an increase in the percentage of Foxp3+ T cells. In APC/T cell co-cultures, mature dendritic cells (DC) were less efficient than immature DC in their ability to support Th17 cell differentiation, while CTLA4-Ig, an agent blocking CD28/B7 and CTLA4/B7 interactions, facilitated both murine and human Th17 differentiation. This study identifies the importance of B7 co-stimulatory molecules in the negative regulation of Th17 development. These unexpected results caution targeting the CD28/B7 pathways in the treatment of human autoimmune diseases.

Basophils are recruited to inflamed lungs and exacerbate memory Th2 responses in mice and humans.

Although the contribution of basophils as inducers or amplifiers of Th2 responses is still debated, prolonged basophil/CD4 T cell interactions were observed in lungs but not lymph nodes (LNs) of parasite‐infected mice. However, the impact of basophils on the function of tissue CD4 effector T cells remains unknown.

Human basophils interact with memory T cells to augment Th17 responses

Basophils are a rare population of granulocytes that have long been associated with IgE-mediated and Th2-associated allergic diseases. However, the role of basophils in Th17 and/or Th1 diseases has not been reported. In the present study, we report that basophils can be detected in the mucosa of Th17-associated lung and inflammatory bowel disease and accumulate in inflamed colons containing large quantities of IL-33. We also demonstrate that circulating basophils increased memory Th17 responses. Accordingly, IL-3- or IL-33-activated basophils amplified IL-17 release in effector memory T cells (T(EM)), central memory T cells (T(CM)), and CCR6(+) CD4 T cells. More specifically, basophils promoted the emergence of IL-17(+)IFN-γ(-) and IL-17(+)IFN-γ(+), but not IL-17(-)IFN-γ(+) CD4 T cells in T(EM) and T(CM). Mechanistic analysis revealed that the enhancing effect of IL-17 production by basophils in T(EM) involved the ERK1/2 signaling pathway, occurred in a contact-independent manner, and was partially mediated by histamine via H(2) and H(4) histamine receptors. The results of the present study reveal a previously unknown function for basophils in augmenting Th17 and Th17/Th1 cytokine expression in memory CD4 T cells. Because basophils accumulated in inflamed inflammatory bowel disease tissues, we propose that these cells are key players in chronic inflammatory disorders beyond Th2.

Selected commensal-related bacteria and Toll-like receptor 3 agonist combinatorial codes synergistically induce interleukin-12 production by dendritic cells to trigger a T helper type 1 polarizing programme

Enteric infections remain a major health problem causing millions of deaths in developing countries. The interplay among the host intestinal epithelium, the mucosa‐associated immune system and microbiota performs an essential role in gut homeostasis and protection against infectious diseases. Dendritic cells (DCs) play a key role in orchestrating protective immunity and tolerance in the gut. The mechanisms by which DCs adapt their responses and discriminate between virulent microbes and trillions of innocuous bacteria remain ill‐defined. Here we investigated the effect of cross‐talk between commensal‐related bacteria (CB) and Toll‐like receptor (TLR) agonists on DC activation and the outcome of the in vitro T helper response. Human monocyte‐derived DCs were exposed to eight different Gram‐positive or Gram‐negative CB strains prior to activation with five different TLR agonists. The key polarizing cytokines interleukin (IL)‐12p70, IL‐10, IL‐1β and IL‐6 were quantified and the fate of naïve T‐cell differentiation was evaluated. We identified a unique combination of Lactobacillus casei and TLR3 signals that acted in synergy to selectively increase IL‐12p70 secretion. Exposure to poly(I:C) converted L. casei‐treated DCs into potent promoters of T helper type 1 (Th1) responses. We propose that DCs can integrate harmless and dangerous non‐self signals delivered by viral products, to mount robust Th1 responses. Thus, in vivo DC targeting with selective probiotics may improve strategies for the management of enteric diseases.

The aryl hydrocarbon receptor (AhR) ligand VAF347 selectively acts on monocytes and naïve CD4+ Th cells to promote the development of IL-22-secreting Th cells

The low molecular weight compound VAF347, and its pro-drug version VAG539, interact with the transcription factor aryl hydrocarbon receptor (AhR) on monocytes to mediate its anti-inflammatory activity in vitro and in vivo. AhR is a crucial factor for IL-22 production, which regulates skin and gut homeostasis. Here we investigated whether VAF347 might control the differentiation of naïve T cells into IL-22-secreting cells and/or regulate IL-22 production by memory T cells. Human monocytes exposed to VAF347 differentiated into dendritic cells capable of instructing a naïve CD4(+) T cell differentiation program that promoted IL-22 secretion and concomitantly inhibited IL-17 production. Whilst AhR ligation by VAF347 on naïve CD4(+) T cells favored the development of single IL-22-secreting cells (Th22), it suppressed the generation of T cells secreting either IL-22 and IFN-γ or IL-17 and IFN-γ. In contrast, memory T cells were refractory to AhR regulation since VAF347, AhR antagonist or AhR gene silencing did not modulate the production of any of these cytokines. Interfering with AhR functions using VAF347 may provide an efficient way to intervene with autoimmune disease since it would enhance the host protective function mediated by IL-22 while preventing the development of Th cells secreting pro-inflammatory cytokines.

CD47Low Status on CD4 Effectors Is Necessary for the Contraction/Resolution of the Immune Response in Humans and Mice

How do effector CD4 T cells escape cell death during the contraction of the immune response (IR) remain largely unknown. CD47, through interactions with thrombospondin-1 (TSP-1) and SIRP-α, is implicated in cell death and phagocytosis of malignant cells. Here, we reported a reduction in SIRP-α-Fc binding to effector memory T cells (TEM) and in vitro TCR-activated human CD4 T cells that was linked to TSP-1/CD47-induced cell death. The reduced SIRP-α-Fc binding (CD47low status) was not detected when CD4 T cells were stained with two anti-CD47 mAbs, which recognize distinct epitopes. In contrast, increased SIRP-α-Fc binding (CD47high status) marked central memory T cells (TCM) as well as activated CD4 T cells exposed to IL-2, and correlated with resistance to TSP-1/CD47-mediated killing. Auto-aggressive CD4 effectors, which accumulated in lymph nodes and at mucosal sites of patients with Crohn’s disease, displayed a CD47high status despite a high level of TSP-1 release in colonic tissues. In mice, CD47 (CD47low status) was required on antigen (Ag)-specific CD4 effectors for the contraction of the IR in vivo, as significantly lower numbers of Ag-specific CD47+/+CD4 T cells were recovered when compared to Ag-specific CD47−/− CD4 T cells. In conclusion, we demonstrate that a transient change in the status of CD47, i.e. from CD47high to CD47low, on CD4 effectors regulates the decision-making process that leads to CD47-mediated cell death and contraction of the IR while maintenance of a CD47high status on tissue-destructive CD4 effectors prevents the resolution of the inflammatory response.

CD47 fusion protein targets CD172a+ cells in Crohn’s disease and dampens the production of IL-1β and TNF

CD172a+ cells producing IL-1β and TNF are increased in inflamed tissues in Crohn’s disease and can be targeted by CD47 fusion protein.