Regulation of T cell activation by TLR ligands. Eur J Cell Biol. 2011;90:582-592. [PMID: 21292344 DOI: 10.1016/j.ejcb.2010.11.012]

Engineered Salmonella carrying siRNA-PD-1 shrinks orthotopically implanted bladder cancer in rats

BACKGROUND

Currently, the application of engineered bacteria in tumour treatment has received increasing attention. It has been proved that Bacillus Calmette-Guerin (BCG) can effectively treat bladder cancer (BC). In addition, immune checkpoint blockade is an effective method for tumour treatment. Programmed cell death protein 1 (PD-1), an important immunosuppressive molecule, binds to programmed death ligand receptor 1 (PD-L1) and inhibits the anti-tumour effects of T cells.

METHODS

The plasmid encoding siRNA-PD-1 was constructed, and the rat BC in situ model was established. After the treatment, morphological changes in tumour tissue were detected by HE staining, and the apoptotic cells in tumour tissue were detected by TUNEL. The expression of related proteins was detected by Western blotting, and the proportion of CD4+ and CD8+ T cells in the spleen was detected by flow cytometry.

RESULTS

We found that the engineered Salmonella significantly inhibited the growth and incidence of tumours and increased the apoptosis of tumours. Importantly, engineered Salmonella carrying siRNA-PD-1 enhanced the anti-tumour immune response by inhibiting PD-1 expression and increased the CD8+ T cell infiltration in tumour tissue, while elevating the ratio of CD8+/CD4+ in spleens.

CONCLUSION

We demonstrated that engineered Salmonella siRNA-PD-1 exerted significant anti-tumour effects on BC.

T cell receptor activation contributes to brain damage after intracerebral hemorrhage in mice

BACKGROUND

Our previous studies demonstrated that activated T cells accumulate in perihematomal regions following intracerebral hemorrhage (ICH) and exacerbate hemorrhagic brain injury. In the present study, we aimed to explore the mechanisms underlying brain-infiltrating T cell activation and the associated pathophysiological effects in neurological outcomes following ICH.

METHODS

We employed standardized collagenase injection-induced and autologous blood injection models of ICH in male C57BL/6J mice. T cell receptor (TCR) activation, immune cell infiltration, and cytokine production were quantified through immunostaining, flow cytometry, and cytokine arrays at 1- and 3-days post-ICH. Brain edema volume was measured at 3 days post-ICH and neurobehavioral assessments were conducted up to 14 days post-ICH. Pharmacological inhibition of TCR activation was achieved using the TCR-specific inhibitor AX-024, administered intraperitoneally at a dosage of 10 mg/kg 1-hour post-ICH.

RESULTS

Flow cytometry and immunostaining detected TCR activation of brain-infiltrating T cells. Specific TCR activation inhibitor AX-024 administration markedly reduced TCR activation and the production of pro-inflammatory cytokines in the brain at 1- and 3-days post-ICH. Moreover, AX-024 administration led to a significant reduction in the infiltration of other leukocyte populations, and significantly reduced brain edema while improved long-term sensorimotor and cognitive outcomes up to 14 days post-ICH.

DISCUSSION

Our findings underscore the critical role of TCR activation in the mobilization and activation of brain-infiltrating T cells post-ICH. Inhibition of TCR activation via AX-024 administration might be developed as a promising therapeutic strategy to improve neurological outcomes following ICH. However, further research is necessary to thoroughly explore the complex pathophysiological processes involved.

Exogenous PD-L1 binds to PD-1 to alleviate and prevent autism-like behaviors in maternal immune activation-induced male offspring mice

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder caused by the interaction of multiple pathogenic factors. Epidemiological studies and animal experiments indicate that maternal immune activation (MIA) is closely related to the development of ASD in offspring. A large number of pro-inflammatory cytokines are transferred from the placenta to the fetal brain during MIA, which impedes fetal neurodevelopment and is accompanied by activation of immune cells and microglia. Programmed cell death protein 1 (PD-1) can be highly expressed on the surface of various activated immune cells, when combined with programmed cell death-ligand 1 (PD-L1), it can activate the PD-1/PD-L1 pathway and exert powerful immunosuppressive effects, suggesting that this immune checkpoint may have the potential to treat MIA-induced ASD. This study combined bioinformatics analysis and experimental validation to explore the efficacy of Fc-fused PD-L1 (PD-L1-Fc) in treating MIA-induced ASD. Bioinformatics analysis results showed that in human placental inflammation, IL-6 was upregulated, T cells proliferated significantly, and the PD-1/PD-L1 pathway was significantly enriched. The experimental results showed that intraperitoneal injection of poly(I:C) induced MIA in pregnant mice resulted in significant expression of IL-6 in their serum, placenta, and fetal brain. At the same time, the expression of PD-1 and PD-L1 in the placenta and fetal brain increased, CD4+ T cells in the spleen were significantly activated, and PD-1 expression increased. Their offspring mice exhibited typical ASD-like behaviors. In vitro experiments on primary microglia of offspring mice have confirmed that the expression of IL-6, PD-1, and PD-L1 is significantly increased, and PD-L1-Fc effectively reduced their expression levels. In the prefrontal cortex of MIA offspring mice, there was an increase in the expression of IL-6, PD-1, and PD-L1; activation of microglial cells, and colocalization with PD-1. Then we administered brain stereotaxic injections of PD-L1-Fc to MIA offspring mice and intraperitoneal injections to MIA pregnant mice. The results indicated that PD-L1-Fc effectively suppressed neuroinflammation in the frontal cortex of offspring mice and partially ameliorated ASD-like behaviors; MIA in pregnant mice was significantly alleviated, and the offspring mice they produced did not exhibit neuroinflammation or ASD-like behaviors. In summary, we have demonstrated the therapeutic ability of PD-L1-Fc for MIA-induced ASD, aiming to provide new strategies and insights for the treatment of ASD.

The effect of the "Oral-Gut" axis on periodontitis in inflammatory bowel disease: A review of microbe and immune mechanism associations

Periodontitis and inflammatory bowel diseases (IBD) are inflammatory diseases of the gastrointestinal tract that share common features of microbial-induced ecological dysregulation and host immune inflammatory response. The close relationship between periodontitis and IBD is characterized by a higher prevalence of IBD in patients with periodontitis and a higher prevalence and severity of periodontitis in patients with IBD, indicating that periodontitis and IBD are different from the traditional independent diseases and form an "Oral-Gut" axis between the two, which affect each other and thus form a vicious circle. However, the specific mechanisms leading to the association between the two are not fully understood. In this article, we describe the interconnection between periodontitis and IBD in terms of microbial pathogenesis and immune dysregulation, including the ectopic colonization of the gut by pathogenic bacteria associated with periodontitis that promotes inflammation in the gut by activating the host immune response, and the alteration of the oral microbiota due to IBD that affects the periodontal inflammatory response. Among the microbial factors, pathogenic bacteria such as Klebsiella, Porphyromonas gingivalis and Fusobacterium nucleatum may act as the microbial bridge between periodontitis and IBD, while among the immune mechanisms, Th17 cell responses and the secreted pro-inflammatory factors IL-1β, IL-6 and TNF-α play a key role in the development of both diseases. This suggests that in future studies, we can look for targets in the "Oral-Gut" axis to control and intervene in periodontal inflammation by regulating periodontal or intestinal flora through immunological methods.

The Effect of Novel Selenopolysaccharide Isolated from Lentinula edodes Mycelium on Human T Lymphocytes Activation, Proliferation, and Cytokines Synthesis

Polysaccharides isolated from Lentinula edodes are bioactive compounds with immunomodulatory properties. In our previous studies from L. edodes mycelium, we have isolated a selenium(Se)-enriched fraction (named Se-Le-30), a mixture of linear 1,4-α-glucan and linear 1,3-β- and 1,6-β-glucans. In this study, we analyzed the effects of Se-Le-30 on the activation and proliferation of human T lymphocytes stimulated by anti-CD3 and anti-CD3/CD28 antibodies (Abs) and on the production of cytokines by peripheral blood mononuclear cells (PBMCs). Se-Le-30 had effects on T cell proliferation induced by Abs against CD3 and CD28. It significantly inhibited the proliferation of CD3-stimulated CD4⁺ and CD8⁺ T cells and enhanced the proliferation of CD4⁺ T cells stimulated with anti-CD3/CD28 Ab. Moreover, Se-Le-30 downregulated the number of CD3-stimulated CD4⁺CD69⁺ cells, CD4⁺CD25⁺ cells, as well as CD8⁺CD25⁺ cells, and upregulated the expression of CD25 marker on CD4+ and CD8+ T cells activated with anti-CD3/CD28 Abs. Furthermore, Se-Le-30 enhanced the synthesis of IFN-γ by the unstimulated and anti-CD3/CD28-stimulated PBMCs, inhibited synthesis of IL-2 and IL-4 by CD3-stimulated cells, and augmented the synthesis of IL-6 and IL-10 by unstimulated, CD3-stimulated, and CD3/CD28-stimulated PBMCs. Together, we demonstrated that Se-Le-30 exerts immunomodulatory effects on human T lymphocytes. These observations are of importance for the prospective use of Se-Le-30 in research or as a therapeutic compound.

Immunostimulatory effects of dairy probiotic strains Bifidobacterium animalis ssp. lactis HY8002 and Lactobacillus plantarum HY7717

Previous studies reported that Bifidobacterium animalis ssp. lactis HY8002 (HY8002) improved intestinal integrity and had immunomodulatory effects. Lactobacillus plantarum HY7717 (HY7717) was screened in vitro from among 21 other lactic acid bacteria (LAB) and demonstrated nitric oxide (NO) production. The aims of this study were to investigate the individual and combined ex vivo and in vivo effects of LAB strains HY8002 and HY7717 at immunostimulating mice that have been challenged with an immunosuppressant drug. The combination of HY8002 and HY7717 increased the secretion of cytokines such as interferon (IFN)-γ, interleukin (IL)-12, and tumor necrosis factor (TNF)-α in splenocytes. In a cyclophosphamide (CTX)-induced immunosuppression model, administration of the foregoing LAB combination improved the splenic and hematological indices, activated natural killer (NK) cells, and up-regulated plasma immunoglobulins and cytokines. Moreover, this combination treatment increased Toll-like receptor 2 (TLR2) expression. The ability of the combination treatment to upregulate IFN-γ and TNF-α in the splenocytes was inhibited by anti-TLR2 antibody. Hence, the immune responses stimulated by the combination of HY8002 and HY7717 are associated with TLR2 activation. The preceding findings suggest that the combination of the HY8002 and HY7717 LAB strains could prove to be a beneficial and efficacious immunostimulant probiotic supplement. The combination of the two probiotic strains will be applied on the dairy foods including yogurt and cheese.

Glucose metabolism characteristics and TLR8-mediated metabolic control of CD4+ Treg cells in ovarian cancer cells microenvironment

Immunotherapy is expected to become the most promising new treatment for ovarian cancer owing to its immunogenicity. However, immunosuppression in the tumor microenvironment is a major obstacle to the efficacy of tumor therapy. Studies have found different metabolism ways of regulatory T cells (Tregs) in the cancer environment may be related to the immunosuppression and Toll-like receptor 8 (TLR8) can reverse the suppression function of Tregs. But it is still unclear that if the TLR8-mediated function reversal is associated with the change of glucose metabolism of Tregs. It was found that the positive expression rates of Glut1, HIF-1α, and Ki67 in CD4⁺ Treg cells of OC were significantly higher than that in benign ovarian tumor and HC, and also significantly higher than that in CD4⁺ Teffs of OC. What’s more, compared with CD4⁺ Teff group, CD4⁺ Tregs highly expressed seven genes and three proteins related to glucose metabolism and had higher levels of glucose uptake and glycolysis. After activating TLR8 signal of CD4⁺ Tregs, the proliferation level of naive CD4⁺ T cells was higher than that of the control group. At the same time, the expression levels of eight genes and five proteins related to glucose metabolism in CD4⁺ Treg cells with TLR8 activated were decreased and levels of glucose uptake and glycolysis were also lower. Furthermore, TLR8 signaling also downregulated the mTOR pathway in CD4⁺ Tregs. CD4⁺ Tregs pretreated with 2-deoxy-d-Glucose (2-DG) and galloflavin also attenuated the inhibition of Teffs proliferation. Although CD4⁺ Tregs pretreated with 2-DG and galloflavin before activating TLR8 signal had no significant difference compared with the group only treated with inhibitors, which suggested TLR8-mediated reversal of CD4⁺ Treg cells inhibitory function in ovarian cancer cells co-cultured microenvironment had a causal relationship with glucose metabolism.

The effect of Toll-like receptor stimulation on the motility of regulatory T cells

Regulatory T cells (Tregs) have suppressive functions and play an important role in controlling inflammation and autoimmunity. The migratory capacity of Tregs determines their location and their location determines whether they inhibit the priming of naïve lymphocytes in lymphoid tissues or the effector phase of immune responses at inflamed sites. Tregs generated or expanded in vitro are currently being tested in clinics for the treatment of autoimmune disorders, however, little is known about the factors controlling their migration towards therapeutically relevant locations. In this study, we have modulated Treg dynamics using Toll-like receptor (TLR) agonists. Dynamic imaging with confocal and two-photon microscopy revealed that Tregs generated in vitro and stimulated with P3C (a TLR2 agonist) but not with R848 (a TLR7 agonist) or LPS (a TLR4 agonist) showed enhanced cell migration within splenic white pulp or draining lymph node when transferred into mice intravenously or into the footpad, respectively. In summary, our data demonstrate that Tregs are more motile in response to direct TLR stimulation in particular towards TLR2 signals. This may have implications for efficient clinical Treg induction protocols.

A mono-acyl phospholipid (20:1 lyso-PS) activates Toll-Like Receptor 2/6 hetero-dimer

Toll-like receptor 2 (TLR2) is an important pattern recognition receptor on the surface of host immune cells that binds a variety of ligands that are released by microorganisms as well as by damaged or dying host cells. According to the current concept, TLR2/1 and TLR2/6 heterodimers are activated by tri- or di-acylated ligands, respectively. However, also mono-acyl phospholipid containing lipid fractions derived from parasites, were reported to be able to activate TLR2. In order to provide conclusive evidence for the TLR2 activating capacity of mono-acyl phospholipids derived from pathogens, we developed a biosynthetic method to enzymatically convert commercially available phospholipids into several mono-acyl-phospholipid variants that were examined for their TLR2 activating capacity. These investigations demonstrated that 1-(11Z-eicosenoyl)-glycero-3-phosphoserine 20:1 (20:1 lyso-PS) is a true agonist of the TLR2/6 heterodimer and that its polar headgroup as well as the length of the acyl chain are crucial for TLR2 activation. In silico modelling further confirmed 20:1 mono-acyl PS as a ligand for TLR2/6 heterodimer, as this predicted that multiple hydrogen bonds are formed between the polar headgroup of 20:1 mono-acyl PS and amino acid residues of both TLR2 and TLR6. Future studies can now be performed to further assess the functions of 20:1 lyso-PS as an immunological mediator, because this enzymatic method enables its preparation in larger quantities than is possible by isolation from the parasite that naturally produces this compound, Schistosoma mansoni, the source of the original discovery (Van der Kleij et al., 2002).

Nanomedicine-mediated alteration of the pharmacokinetic profile of small molecule cancer immunotherapeutics

The advent of immunotherapy is a game changer in cancer therapy with monoclonal antibody- and T cell-based therapeutics being the current flagships. Small molecule immunotherapeutics might offer advantages over the biological drugs in terms of complexity, tissue penetration, manufacturing cost, stability, and shelf life. However, small molecule drugs are prone to rapid systemic distribution, which might induce severe off-target side effects. Nanotechnology could aid in the formulation of the drug molecules to improve their delivery to specific immune cell subsets. In this review we summarize the current efforts in changing the pharmacokinetic profile of small molecule immunotherapeutics with a strong focus on Toll-like receptor agonists. In addition, we give our vision on limitations and future pathways in the route of nanomedicine to the clinical practice.

Identification and validation of a novel dual small-molecule TLR2/8 antagonist

Toll-like receptor 2 (TLR2) and TLR8 are involved in the recognition of bacterial and viral components and are linked not only to protective antimicrobial immunity but also to inflammatory diseases. Recently, increasing attention has been paid to the receptor crosstalk between TLR2 and TLR8 to fine-tune innate immune responses. In this study, we report a novel dual TLR2/TLR8 antagonist, compound 24 that was developed by a modeling-guided synthesis approach. The modulator was optimized from the previously reported 1,3-benzothiazole derivative, compound 8. Compound 24 was pharmacologically characterized for the ability to inhibit TLR2- and TLR8-mediated responses in TLR-overexpressing reporter cells and THP-1 macrophages. The modulator showed high efficacy with IC₅₀ values in the low micromolar range for both TLRs, selectivity towards other TLRs and low cytotoxicity. At TLR2, a slight predominance for the TLR2/1 heterodimer was found in reporter cells selectively expressing TLR2/1 or TLR2/6 heterodimers. Concentration ratio analysis in the presence of Pam₃CSK₄ or Pam₂CSK₄ indicated non-competitive antagonist behavior at hTLR2. In computational docking studies, a plausible alternative binding mode of compound 24 was predicted for both TLR2 and TLR8. Our results provide evidence that it is feasible to simultaneously and selectively target endosomal- and surface-located TLRs. We identified a small-molecule dual TLR2/8 antagonist that may serve as a valuable pharmacological tool to decipher the role of TLR2/8 co-signaling in inflammation.

Activation of Human γδ T Cells: Modulation by Toll-Like Receptor 8 Ligands and Role of Monocytes

Background: Human Vγ9Vδ2 γδ T cells can kill a variety of cancer cells and have attracted substantial interest for cancer immunotherapy. Toll-like receptor (TLR) ligands are promising adjuvants for cancer immunotherapy, but TLR7/8 ligand Resiquimod has been shown to inhibit CD4 T-cell activation in a monocyte-dependent manner. Therefore, we studied the modulation of human γδ T-cell activation by TLR7/8 ligands. Methods: Peripheral blood mononuclear cells (PBMC) or purified γδ T cells together with purified monocytes were stimulated with zoledronic acid or phosphoantigens in the absence or presence of various imidazoquinoline TLR7 or TLR8 agonists. Read-out systems included interferon-γ induction and cellular expansion of γδ T cells, as well as viability, cell surface antigen modulation, and IL-1β and TNF-α production of monocytes. Results: TLR8 ligand TL8-506 and TLR7/8 ligand Resiquimod (but not TLR7 ligands) rapidly induced IFN-γ expression in γδ T cells within PBMC, and co-stimulated phosphoantigen-induced IFN-γ expression in γδ T cells. On the other hand, TLR8 ligands potently suppressed γδ T-cell expansion in response to zoledronic acid and phosphoantigen. Purified monocytes secreted large amounts of IL-1β and TNF-α when stimulated with TLR8 ligands but simultaneously underwent substantial cell death after 24 h. Conclusions: TLR8 ligand-activated monocytes potently co-stimulate early γδ T-cell activation but failed to provide accessory cell function for in vitro expansion of γδ T cells.

Sensing of HIV-1 by TLR8 activates human T cells and reverses latency

During HIV infection, cell-to-cell transmission results in endosomal uptake of the virus by target CD4+ T cells and potential exposure of the viral ssRNA genome to endosomal Toll-like receptors (TLRs). TLRs are instrumental in activating inflammatory responses in innate immune cells, but their function in adaptive immune cells is less well understood. Here we show that synthetic ligands of TLR8 boosted T cell receptor signaling, resulting in increased cytokine production and upregulation of surface activation markers. Adjuvant TLR8 stimulation, but not TLR7 or TLR9, further promoted T helper cell differentiation towards Th1 and Th17. In addition, we found that endosomal HIV induced cytokine secretion from CD4+ T cells in a TLR8-specific manner. TLR8 engagement also enhanced HIV-1 replication and potentiated the reversal of latency in patient-derived T cells. The adjuvant TLR8 activity in T cells can contribute to viral dissemination in the lymph node and low-grade inflammation in HIV patients. In addition, it can potentially be exploited for therapeutic targeting and vaccine development.

Sustaining exposure to high concentrations of bifidobacteria inhibits gene expression of Mouse's mucosal immunity

Numerous dietary products are supplemented with probiotics that may be beneficial for human health. Recently, bifidobacteria have received increasing attention as a genus of probiotic bacteria with high efficiency and few side effects. To examine potential effects of different bifidobacteria concentrations on the mucosal immune response, we fed mice with (a) 10⁸ colony-forming units (CFU) of bifidobacteria (group 10⁸B), and (b) with 10¹² CFU of bifidobacteria (group 10¹²B) over 42 days and assessed gene expression in intestinal mucosa and immune marker concentrations in serum samples; ten untreated female mice were used as a control. Continuous exposure to 10⁸ CFU of bifidobacteria activated both macrophages and T_reg immune cells through significantly increasing the expression of mucosal TLR2 and IL10-mRNA genes, but inhibited Th1 and Th2 cells via significant downregulation of IL4 and IFNγ gene expression, compared to untreated mice. Interestingly, group 10¹²B showed down-regulated expression of TLR2, IL10, and IL4 genes but up-regulated expression of IFNγ, compared to group 10⁸B and to the control. Also, polyclonal immunoglobulins IgG, IgM, and IgA showed a significant increase in all treated mice compared to the control. We conclude that high concentrations of bifidobacteria reduced innate immune functions. Furthermore, adaptive immunity seemed to be enhanced by increasing stimulation of T and B lymphocytes, suggesting aberration of the immune system following intestinal inflammation due to constant exposure to high concentrations of bifidobacteria. Both experimental bifidobacteria concentrations increased the total levels of circulating Igs, particularly of IgA.

T Cell Proliferation Is Induced by Chronically TLR2-Stimulated Gingival Fibroblasts or Monocytes

During inflammation of the gums, resident cells of the periodontium, gingival fibroblasts (GFs), interact with heterogeneous cell populations of the innate and adaptive immune system that play a crucial role in protecting the host from pathogenic infectious agents. We investigated the effects of chronic inflammation, by exposing peripheral blood mononuclear cells (PBMCs), peripheral blood lymphocyte (PBL) cultures, and GF–PBMC cocultures to Toll-like receptor 2 (TLR2) and TLR4 activators for 21 days and assessed whether this influenced leukocyte retention, survival, and proliferation. Chronic stimulation of PBMC–GF cocultures with TLR2 and TLR4 agonists induced a reduction of NK (CD56+CD3−), T (CD3+), and B (CD19+) cells, whereas the number of TLR-expressing monocytes were unaffected. TLR2 agonists doubled the T cell proliferation, likely of a selective population, given the net decrease of T cells. Subsequent chronic exposure experiments without GF, using PBMC and PBL cultures, showed a significantly (p < 0.0001) increased proinflammatory cytokine production of TNF-α and IL-1β up to 21 days only in TLR2-activated PBMC with concomitant T cell proliferation, suggesting a role for monocytes. In conclusion, chronic TLR activation mediates the shift in cell populations during infection. Particularly, TLR2 activators play an important role in T cell proliferation and proinflammatory cytokine production by monocytes, suggesting that TLR2 activation represents a bridge between innate and adaptive immunity.

The Contribution of the Immune System in Bone Metastasis Pathogenesis

Bone metastasis is associated with significant morbidity for cancer patients and results in a reduced quality of life. The bone marrow is a fertile soil containing a complex composition of immune cells that may actually provide an immune-privileged niche for disseminated tumor cells to colonize and proliferate. In this unique immune milieu, multiple immune cells including T cells, natural killer cells, macrophages, dendritic cells, myeloid-derived suppressor cells, and neutrophils are involved in the process of bone metastasis. In this review, we will discuss the crosstalk between immune cells in bone microenvironment and their involvement with cancer cell metastasis to the bone. Furthermore, we will highlight the anti-tumoral and pro-tumoral function of each immune cell type that contributes to bone metastasis. We will end with a discussion of current therapeutic strategies aimed at sensitizing immune cells.

Damage-associated molecular patterns in inflammatory bowel disease: From biomarkers to therapeutic targets

The chronic inflammatory process underlying inflammatory bowel disease (IBD), comprising Crohn's disease and ulcerative colitis, derives from the interplay of several components in a genetically susceptible host. These components include environmental elements and gut microbiota a dysbiosis. For decades, immune abnormalities have been investigated as critically important in IBD pathogenesis, and attempts to develop effective therapies have predominantly targeted the immune system. Nevertheless, immune events represent only one of the constituents contributing to IBD pathogenesis within the context of the complex cellular and molecular network underlying chronic intestinal inflammation. These factors need to be appreciated within the milieu of non-immune components. Damage-associated molecular patterns (DAMPs), which are essentially endogenous stress proteins expressed or released as a result of cell or tissue damage, have been shown to act as direct pro-inflammatory mediators. Excessive or persistent signalling mediated by such molecules can underlie several chronic inflammatory disorders, including IBD. The release of endogenous DAMPs amplifies the inflammatory response driven by immune and non-immune cells and promotes epigenetic reprogramming in IBD. The effects determine pathologic changes, which may sustain chronic intestinal inflammation and also underlie specific disease phenotypes. In addition to highlighting the potential use of DAMPs such as calprotectin as biomarkers, research on DAMPs may reveal novel mechanistic associations in IBD pathogenesis and is expected to uncover putative therapeutic targets.

In vitro and in vivo evidences for innate immune stimulators lactic acid bacterial starters isolated from fermented camel dairy products

Probiotics are commensals with special characteristics that are essential for the development of the immune system, and may protect mucosal surfaces against pathogens. In this study, a total of 40 lactic acid bacteria (LAB) were isolated from different raw and fermented camel's milk samples collected from Saudi Arabia (Makkah area) and Egypt (Fayoum), and tested for the probiotic properties. Among them, Pro 4 and Pro 7 isolates exhibited excellent probiotic potential including bile salt (0.2-0.6%), phenol tolerance (0.2-0.4%) and salt tolerance (0.0-10%). Furthermore, both strains exhibited antimicrobial activity against wide range of food-borne pathogens and Dermatophytes with average zone inhibition of 37.5, 35.5, 34.5, 27.5, 25 and 23.5 mm for Staphylococcus aureus, Trichophyton mentagrophytes, Escherichia coli, Listeria monocytogens, Candida albicans and Salmonella typhi, respectively. Furthermore, the in vivo study indicated that these strains significantly improved the mucosal immune responses through an increase in expression of TLR2 and IFNγ mRNA in mice intestine as well as increased the synthesis of polyclonal IgG, IgM and IgA in mice blood sera. Accordingly, due to these unique probiotic properties, both selected strains could be potentially used as probiotic starter cultures for fermented dairy foods as well as functional food and health products.

Recent advances in CD8+ regulatory T cell research

Various subgroups of CD8⁺ T lymphocytes do not only demonstrate cytotoxic effects, but also serve important regulatory roles in the body's immune response. In particular, CD8⁺ regulatory T cells (CD8⁺ Tregs), which possess important immunosuppressive functions, are able to effectively block the overreacting immune response and maintain the body's immune homeostasis. In recent years, studies have identified a small set of special CD8⁺ Tregs that can recognize major histocompatibility complex class Ib molecules, more specifically Qa-1 in mice and HLA-E in humans, and target the self-reactive CD4⁺ T ce lls. These findings have generated broad implications in the scientific community and attracted general interest to CD8⁺ Tregs. The present study reviews the recent research progress on CD8⁺ Tregs, including their origin, functional classification, molecular markers and underlying mechanisms of action.

IL-17A-Producing Foxp3+ Regulatory T Cells and Human Diseases

CD4+Foxp3+ regulatory T (Treg) cells play major roles in immune homeostasis. While CD4+Foxp3+ Treg cells act to suppress other immune effector cells, there is growing evidence that they also produce pro-inflammatory cytokines, such as IL-17A, in inflammatory conditions. The pro-inflammatory cytokine milieu, toll-like receptor (TLR) signaling, and specific transcription factors are important for the production of IL-17A by CD4+Foxp3+ Treg cells. In particular, IL-17A-producing CD4+Foxp3+ Treg cells express RORγt, the T helper (Th) 17-specific transcription factor, in addition to Foxp3. IL-17A-producing CD4+Foxp3+ Treg cells are also involved in the pathogenesis of various diseases. Here we review the mechanisms underlying the induction of IL-17A-producing CD4+Foxp3+ Treg cells and the roles of these cells in human disease.

Cutting Edge: Activation of STING in T Cells Induces Type I IFN Responses and Cell Death

Stimulator of interferon genes (STING) was initially described as a sensor of intracellular bacterial and viral DNA and a promising adjuvant target in innate immune cells; more recently STING has also been shown to detect endogenous DNA and play a role in tumor immunity and autoimmune disease development. Thus far STING has been studied in macrophages and dendritic cells. In this study, to our knowledge we provide the first evidence of STING activation in T cells, in which STING agonists not only provoke type I IFN production and IFN-stimulated gene expression, mirroring the response of innate cells, but are also capable of activating cell stress and death pathways. Our results suggest a re-evaluation of STING agonist-based therapies may be necessary to identify the possible effects on the T cell compartment. Conversely, the effects of STING on T cells could potentially be harnessed for therapeutic applications.

Antipsychotics influence Toll-like receptor (TLR) expression and its relationship with cognitive functions in schizophrenia

Increasing evidence suggests that altered immune functions are related to the pathophysiology of schizophrenia. Relatively little information is available on Toll-like receptors (TLRs), which are implicated in the recognition of molecular patterns associated with pathogens and internal cellular damage signals. By using immunophenotyping and flow cytometry, we investigated TLRs in CD14+ monocytes, CD4+CD25+Foxp3+ regulatory T cells (T_reg), and CD3+CD4+CD25+ activated T cells (T_act) in 35 drug-naïve patients with schizophrenia before and after an 8-week period of antipsychotic treatment with risperidone or olanzapine. As compared with 30 healthy control individuals, drug-naïve patients with schizophrenia exhibited an increased percentage of TLR4+ and TLR5+ monocytes and TLR5+ T_reg/T_act cells. At the end of the treatment period, we observed normalized TLR4+ monocytes and an up-regulation of TLR2+ monocytes and T_reg/T_act cells. Mean fluorescent intensity values, indicating receptor density, were consistent with these findings. In the drug-naïve state, but not after treatment, higher percentages of TLR4+ and TLR5+ monocytes were correlated with more severe cognitive deficits. Positive, negative, and general clinical symptoms were not associated with TLRs. There were no significant differences between patients receiving olanzapine and risperidone. These results indicate that abnormal expression of TLRs can be detected in the earliest stage of schizophrenia, which is modulated by antipsychotics. Immunological alterations in unmedicated schizophrenia patients may be linked to cognitive deficits.

Diverse action of lipoteichoic acid and lipopolysaccharide on neuroinflammation, blood-brain barrier disruption, and anxiety in mice

Microbial metabolites are known to affect immune system, brain, and behavior via activation of pattern recognition receptors such as Toll-like receptor 4 (TLR4). Unlike the effect of the TLR4 agonist lipopolysaccharide (LPS), the role of other TLR agonists in immune-brain communication is insufficiently understood. We therefore hypothesized that the TLR2 agonist lipoteichoic acid (LTA) causes immune activation in the periphery and brain, stimulates the hypothalamic-pituitary-adrenal (HPA) axis and has an adverse effect on blood-brain barrier (BBB) and emotional behavior. Since LTA preparations may be contaminated by LPS, an extract of LTA (LTAextract), purified LTA (LTApure), and pure LPS (LPSultrapure) were compared with each other in their effects on molecular and behavioral parameters 3h after intraperitoneal (i.p.) injection to male C57BL/6N mice. The LTAextract (20mg/kg) induced anxiety-related behavior in the open field test, enhanced the circulating levels of particular cytokines and the cerebral expression of cytokine mRNA, and blunted the cerebral expression of tight junction protein mRNA. A dose of LPSultrapure matching the amount of endotoxin/LPS contaminating the LTAextract reproduced several of the molecular and behavioral effects of LTAextract. LTApure (20mg/kg) increased plasma levels of tumor necrosis factor-α (TNF-α), interleukin-6 and interferon-γ, and enhanced the transcription of TNF-α, interleukin-1β and other cytokines in the amygdala and prefrontal cortex. These neuroinflammatory effects of LTApure were associated with transcriptional down-regulation of tight junction-associated proteins (claudin 5, occludin) in the brain. LTApure also enhanced circulating corticosterone, but failed to alter locomotor and anxiety-related behavior in the open field test. These data disclose that TLR2 agonism by LTA causes peripheral immune activation and initiates neuroinflammatory processes in the brain that are associated with down-regulation of BBB components and activation of the HPA axis, although emotional behavior (anxiety) is not affected. The results obtained with an LTA preparation contaminated with LPS hint at a facilitatory interaction between TLR2 and TLR4, the adverse impact of which on long-term neuroinflammation, disruption of the BBB and mental health warrants further analysis.

Accumulation Mechanisms of CD4(+)CD25(+)FOXP3(+) Regulatory T Cells in EBV-associated Gastric Carcinoma

Approximately 10% of gastric carcinomas are associated with Epstein-Barr virus (EBV) and are defined as EBV-associated gastric carcinomas (EBVaGCs). EBVaGCs are known to be accompanied by massive CD8⁺ cytotoxic T cell (CTL) infiltration; however, adoptive cellular immunotherapy based on EBV-specific CD8⁺ CTLs has been explored with limited success. Because regulatory T cells (Tregs) are regarded as a critical hurdle in anti-tumour immunity, we assessed the distribution of Tregs in 45 cases of EBVaGC and 45 cases of EBV-negative gastric carcinoma (EBVnGC) with matched clinicopathological parameters by immunohistochemistry. We showed that Tregs were significantly increased in EBVaGC compared to EBVnGC (15.92 ± 11.45/HPF vs. 8.45 ± 6.16/HPF, p = 0.001). In addition, we explored the accumulation mechanisms of Tregs in EBVaGC by using EBV (+) gastric carcinoma cell lines SNU719 and GT39 as ex vivo models. When peripheral blood mononuclear cells (PBMCs) were co-cultured with EBV (+) gastric carcinoma cell lines, the Treg frequency increased, and they underwent phenotypic and functional changes. The enhanced recruitment by CCL22 produced by EBVaGC cells, the decreased emigration due to CCR7 downregulation on the Treg surface, the higher proliferation rate, and the lower apoptosis rate of Tregs at tumour sites may promote the accumulation of Tregs in EBVaGC.

Expression of Toll-Like Receptors 2 and 4 and Related Cytokines in Patients with Hepatic Cystic and Alveolar Echinococcosis

Several studies have demonstrated the important role of Toll-like receptors in various parasitic infections. This study aims to explore expression of Toll-like receptors (TLRs) and related cytokines in patients with human cystic echinococcosis (CE) and alveolar echinococcosis (AE). 78 subjects including AE group (N = 28), CE group (N = 22), and healthy controls (HC, N = 28) were enrolled in this study. The mRNA expression levels of TLR2 and TLR4 in blood and hepatic tissue and plasma levels related cytokines were detected by using ELISA. Median levels of TLR2 mRNA in AE and CE groups were significantly elevated as compared with that in healthy control group. Median levels of TLR4 expression were increased in AE and CE. Plasma concentration levels of IL-5, IL-6, and IL-10 were slightly increased in AE and CE groups compared with those in HC group with no statistical differences (p > 0.05). The IL-23 concentration levels were significantly higher in AE and CE groups than that in HC subjects with statistical significance. The increased expression of TLR2 and IL-23 might play a potential role in modulating tissue infiltrative growth of the parasite and its persistence in the human host.

Mathematical Modeling of Early Cellular Innate and Adaptive Immune Responses to Ischemia/Reperfusion Injury and Solid Organ Allotransplantation

A mathematical model of the early inflammatory response in transplantation is formulated with ordinary differential equations. We first consider the inflammatory events associated only with the initial surgical procedure and the subsequent ischemia/reperfusion (I/R) events that cause tissue damage to the host as well as the donor graft. These events release damage-associated molecular pattern molecules (DAMPs), thereby initiating an acute inflammatory response. In simulations of this model, resolution of inflammation depends on the severity of the tissue damage caused by these events and the patient's (co)-morbidities. We augment a portion of a previously published mathematical model of acute inflammation with the inflammatory effects of T cells in the absence of antigenic allograft mismatch (but with DAMP release proportional to the degree of graft damage prior to transplant). Finally, we include the antigenic mismatch of the graft, which leads to the stimulation of potent memory T cell responses, leading to further DAMP release from the graft and concomitant increase in allograft damage. Regulatory mechanisms are also included at the final stage. Our simulations suggest that surgical injury and I/R-induced graft damage can be well-tolerated by the recipient when each is present alone, but that their combination (along with antigenic mismatch) may lead to acute rejection, as seen clinically in a subset of patients. An emergent phenomenon from our simulations is that low-level DAMP release can tolerize the recipient to a mismatched allograft, whereas different restimulation regimens resulted in an exaggerated rejection response, in agreement with published studies. We suggest that mechanistic mathematical models might serve as an adjunct for patient- or sub-group-specific predictions, simulated clinical studies, and rational design of immunosuppression.

The role of regulatory T cells in cancer immunology

Regulatory T cells (Treg) are generally considered to be significant contributors to tumor escape from the host immune system. Emerging evidence suggests, however, that in some human cancers, Treg are necessary to control chronic inflammation, prevent tissue damage, and limit inflammation-associated cancer development. The dual role of Treg in cancer and underpinnings of Treg diversity are not well understood. This review attempts to provide insights into the importance of Treg subsets in cancer development and its progression. It also considers the role of Treg as potential biomarkers of clinical outcome in cancer. The strategies for monitoring Treg in cancer patients are discussed as is the need for caution in the use of therapies which indiscriminately ablate Treg. A greater understanding of molecular pathways operating in various tumor microenvironments is necessary for defining the Treg impact on cancer and for selecting immunotherapies targeting Treg.

Origin and functions of pro-inflammatory cytokine producing Foxp3+ regulatory T cells

CD4(+)CD25(+)Foxp3(+) regulatory cells (Tregs) are a special lineage of cells central in the maintenance of immune homeostasis, and are targeted for human immunotherapy. They are conventionally associated with the production of classical anti-inflammatory cytokines such as IL-10, TGF-β and IL-35, consistent to their anti-inflammatory functions. However, emerging evidence show that they also express effector cytokines such as IFN-γ and IL-17A under inflammatory conditions. While some studies reveal that these pro-inflammatory cytokine producing Foxp3(+) regulatory cells retain their suppressive ability, others believe that these cells are dys-regulated and are associated with perpetuation of immunopathology. Therefore the development of these cells may challenge the efficacy of human Treg therapy. Mechanistically, toll-like receptor (TLR) ligands and the pro-inflammatory cytokine milieu have been shown to play important roles in the induction of effector cytokines in Tregs. Here we review the mechanisms of development and the possible functions of pro-inflammatory cytokine producing Foxp3+ Tregs.

TLR2-dependent amelioration of allergic airway inflammation by parasitic nematode type II MIF in mice

In our previous studies, the recombinant type II macrophage migration inhibitory factor homologue (rAs-MIF) secreted from Anisakis simplex suppressed experimental inflammation mouse model through IL-10 production and CD4(+)CD25(+)Foxp3(+) T-cell recruitment. Also, TLR2 gene expression was significantly increased following rAs-MIF treatment. To know the relation between TLR2 and amelioration mechanisms of rAs-MIF, we induced allergic airway inflammation by ovalbumin and alum with or without rAs-MIF under TLR2 blocking systems [anti-TLR2-specific antibody (α-mTLR2 Ab) treatment and using TLR2 knockout mice]. As a result, the amelioration effects of rAs-MIF in allergic airway inflammation model (diminished inflammation and Th2 response in the lung, increased IL-10 secretion, CD4(+)CD25(+)Foxp3(+) T-cell recruitment) were diminished under two of the TLR2 blocking model. The expression of TLR2 on the surface of lung epithelial cell was significantly elevated by rAs-MIF treatment or Pam3CSK (TLR2-specific agonist) treatment, but they might have some competition effect on the elevation of TLR2 expression. In addition, the elevation of IL-10 gene expression by rAs-MIF treatment was significantly inhibited by α-mTLR2 Ab or Pam3CSK pretreatment. In conclusion, anti-inflammatory effects of the rAs-MIF on OVA-induced allergic airway inflammation might be closely related to TLR2.

Pathological conditions re-shape physiological Tregs into pathological Tregs

CD4⁺FOXP3⁺ regulatory T cells (Tregs) are a subset of CD4 T cells that play an essential role in maintaining peripheral immune tolerance, controlling acute and chronic inflammation, allergy, autoimmune diseases, and anti-cancer immune responses. Over the past 20 years, significant progress has been made since Tregs were first characterized in 1995. Many concepts and principles regarding Tregs generation, phenotypic features, subsets (tTregs, pTregs, iTregs, and iTreg35), tissue specificity (central Tregs, effector Tregs, and tissue resident Tregs), homeostasis (highly dynamic and apoptotic), regulation of Tregs by receptors for PAMPs and DAMPs, Treg plasticity (re-differentiation to other CD4 T helper cell subsets, Th1, Th2, Tfh and Th17), and epigenetic regulation of Tregs phenotypes and functions have been innovated. In this concise review, we want to briefly analyze these eight new progresses in the study of Tregs. We have also proposed for the first time a novel concept that "physiological Tregs" have been re-shaped into "pathological Tregs" in various pathological environments. Continuing of the improvement in our understanding on this important cellular component about the immune tolerance and immune suppression, would lead to the future development of novel therapeutics approaches for acute and chronic inflammatory diseases, allergy, allogeneic transplantation-related immunity, sepsis, autoimmune diseases, and cancers.

Budesonide increases TLR4 and TLR2 expression in Treg lymphocytes of allergic asthmatics

BACKGROUND

Reduced innate immunity responses as well as reduced T regulatory activities characterise bronchial asthma.

OBJECTIVES

In this study the effect of budesonide on the expression of TLR4 and TLR2 in T regulatory lymphocyte sub-population was assessed.

METHODS

TLR4 and TLR2 expression in total peripheral blood mononuclear cells (PBMC), in CD4+/CD25+ and in CD4+/CD25- was evaluated, by flow cytometric analysis, in mild intermittent asthmatics (n = 14) and in controls (n = 11). The in vitro effects of budesonide in modulating: TLR4 and TLR2 expression in controls and in asthmatics; IL-10 expression and cytokine release (IL-6 and TNF-α selected by a multiplex assay) in asthmatics were also explored.

RESULTS

TLR4 and TLR2 were reduced in total PBMC from asthmatics in comparison to PBMC from controls. CD4+CD25+ cells expressed at higher extent TLR2 and TLR4 in comparison to CD4+CD25- cells. Budesonide was able to increase the expression of TLR4, TLR2 and IL-10 in CD4+/CD25 highly+ cells from asthmatics. TLR4 ligand, LPS induced Foxp3 expression. Budesonide was also able to reduce the release of IL-6 and TNF-α by PBMC of asthmatics.

CONCLUSIONS

Budesonide potentiates the activity of Treg by increasing TLR4, TLR2 and IL-10 expression. This event is associated to the decreased release of IL-6 and TNF-α in PBMC treated with budesonide. These findings shed light on new mechanisms by which corticosteroids, drugs widely used for the clinical management of bronchial asthma, control T lymphocyte activation.

Co-upregulation of Toll-like receptors 2 and 6 on peripheral blood cells in patients with obstructive sleep apnea

PURPOSE

Toll-like receptor (TLR) 2 can heterodimerise with TLR6 to detect diacylated lipoproteins. Hypoxia inducible factor-1 α co-ordinates selective induction of TLR2 and TLR6 during persistent hypoxia. We hypothesized that TLR 2/6 co-expression may be upregulated by chronic intermittent hypoxia with re-oxygenation (IHR) in obstructive sleep apnea (OSA).

METHODS

TLR2/6 expressions on blood immune cells were measured in 144 patients with sleep-disordered breathing (SDB), including primary snoring (PS, n = 24), moderate to severe OSA (MSO, n = 60), very severe OSA (VSO, n = 36), and very severe OSA on continuous positive airway pressure (CPAP) treatment (VSOC, n = 24). An in vitro IHR experiment was also undertaken.

RESULTS

Patients in both the MSO and VSO groups had increased TLR2/6 co-expression on CD16(+) neutrophil than those in the PS group. Patients in the VSOC group had reduced TLR2/6 co-expression on neutrophil than those in either the MSO or VSO group. Blood absolute neutrophil count was positively but weakly correlated with TLR2/6 co-expression on neutrophil. TLR2/6 co-expressions on both CD14(+) monocyte and CD3(+)CD4(+)T helper cell, and TLR2 expressions on both monocyte and T helper cell in SDB patients with low Minimum SaO₂ (≦70%) were all higher than those with high Minimum SaO₂. In vitro IHR for 1-4 days resulted in TLR2/6 co-upregulation on both neutrophil and monocyte.

CONCLUSIONS

OSA patients had increased TLR2/6 co-expressions on blood immune cells, which were related to their immune cell counts and could be reversed with CPAP treatment. In vitro IHR could induce TLR2/6 co-upregulation.

TLR2 Involved in Naive CD4+ T Cells Rescues Stress-Induced Immune Suppression by Regulating Th1/Th2 and Th17

Stress, either physical or psychological, can have a dramatic impact on our immune system. There has been little progress, however, in understanding chronic stress-induced immunosuppression. Naive CD4+ T cells could modulate immune responses via differentiation to T helper (Th) cells. In this study, we showed that stress promotes the release of the Th1 cytokines interferon (IFN)-γ and tumor necrosis factor (TNF)-α, the Th2 cytokines interleukin (IL)-4 and IL-10 and the Th17 cytokine IL-17 of splenic naive CD4+ T cells. This suggests that stress promotes the differentiation of naive CD4+ T cells to Th1, Th2 and Th17 cells. Knockout strategies verified that TLR2 might modulate the differentiation of Th1/Th2 cells by inhibiting p38 mitogen-activated protein kinase (MAPK). Taken together, our data suggest that chronic stress induces immune suppression by targeting TLR2 and p38 MAPK in naive CD4+ T cells.

Regulatory and Effector Helper T-Cell Profile after Nerve Xenografting in the Toll-Like Receptor-Deficient Mice

INTRODUCTION

The balance between regulatory T cells (Tregs) and effector T help cells (Th cells) is critical for the control of adaptive immune response during nerve transplantation. However, whether the homeostasis of immune regulation between Tregs and Th cells requires toll-like receptor (TLR) signaling is unclear. The aim of this study is to profile the distribution of spleen Tregs and Th cells in a mouse model of nerve xenografting in the TLR2 and NF-κB gene knockout mice.

METHODS

The sciatic nerve was taken from a SD rat or an allogeneic mouse and transplanted to a right back leg of recipient C57BL/6, TLR2(-/-), or NF-κB(-/-) mice by subcutaneous transplantation. After 7 days, the T lymphocytes were then isolated from spleen, stained with phenotyping kits, and analyzed by flow cytometry.

RESULTS

The results showed that Tregs were decreased after nerve xenografting in the recipient C57BL/6 mouse. In addition, nerve xenografting also increased the Th1 and Th17 but not the Th2 cell populations. In contrast, amelioration of the Tregs elimination was found in TLR2(-/-) and NF-κB(-/-) mice after transplantation of the nerve xenograft. Moreover, the mice lacking TLR2 or NF-κB showed attenuation of the increase in Th1 and Th17 cells after nerve xenografting.

CONCLUSIONS

TLR signaling is involved in T cell population regulation during tissue transplantation. Knock-out of TLR2 and NF-κB prevented Tregs elimination and inhibited Th1- and Th17-driven immune response after nerve xenografting. This study highlighted the potential of inhibiting TLR signaling to modulate T cell-mediated immune regulation to facilitate tolerance to nerve transplantation.

Immunomodulatory effects of polysaccharide from marine fungus Phoma herbarum YS4108 on T cells and dendritic cells

YCP, as a kind of natural polysaccharides from the mycelium of marine filamentous fungus Phoma herbarum YS4108, has great antitumor potential via enhancement of host immune response, but little is known about the molecular mechanisms. In the present study, we mainly focused on the effects and mechanisms of YCP on the specific immunity mediated by dendritic cells (DCs) and T cells. T cell /DC activation-related factors including interferon- (IFN-) γ, interleukin-12 (IL-12), and IL-4 were examined with ELISA. Receptor knock-out mice and fluorescence-activated cell sorting are used to analyze the YCP-binding receptor of T cells and DCs. RT-PCR is utilized to measure MAGE-A3 for analyzing the tumor-specific killing effect. In our study, we demonstrated YCP can provide the second signal for T cell activation, proliferation, and IFN-γ production through binding to toll-like receptor- (TLR-) 2 and TLR-4. YCP could effectively promote IL-12 secretion and expression of markers (CD80, CD86, and MHC II) via TLR-4 on DCs. Antigen-specific immunity against mouse melanoma cells was strengthened through the activation of T cells and the enhancement of capacity of DCs by YCP. The data supported that YCP can exhibit specific immunomodulatory capacity mediated by T cells and DCs.

The role of TLR8 signaling in acute myeloid leukemia differentiation

Acute myeloid leukemia (AML) is an aggressive disease with a poor 5-year survival of 21% that is characterized by a differentiation arrest of immature myeloid cells. For a rare subtype of AML (acute promyeloctyic leukemia, 5-10% of cases) all-trans retinoic acid therapy removes the differentiation block, yielding over a 90% cure rate. However, this treatment is not effective for the other 90-95% of AML patients, suggesting new differentiation strategies are needed. Interestingly, differentiation is induced in normal hematopoietic cells through Toll-like receptor (TLR) stimulation and TLRs are expressed on AML cells. We present evidence that the TLR8 activation promotes AML differentiation and growth inhibition in a TLR8/MyD88/p38 dependent manner. We also show that that TLR7/TLR8 agonist, R848, considerably impairs the growth of human AML cells in immunodeficient mice. Our data suggests TLR8 activation has direct anti-leukemic effects independent of its immunomodulating properties that are currently under investigation for cancer therapy. Taken together, our results suggest that treatment with TLR8 agonists may be a promising new therapeutic strategy for AML.

Toll-like receptor 2 as a regulator of oral tolerance in the gastrointestinal tract

Food allergy, other adverse immune responses to foods, inflammatory bowel disease, and eosinophilic esophagitis have become increasingly common in the last 30 years. It has been proposed in the "hygiene hypothesis" that dysregulated immune responses to environmental microbial stimuli may modify the balance between tolerance and sensitization in some patients. Of the pattern recognition receptors that respond to microbial signals, toll-like receptors (TLRs) represent the most investigated group. The relationship between allergy and TLR activation is currently at the frontier of immunology research. Although TLR2 is abundant in the mucosal environment, little is known about the complex relationship between bystander TLR2 activation by the commensal microflora and the processing of oral antigens. This review focuses on recent advances in our understanding of the relationship between TLR2 and oral tolerance, with an emphasis on regulatory T cells, eosinophils, B cells, IgA, intestinal regulation, and commensal microbes.

Effects of soluble extracts from Leishmania infantum promastigotes, Toxoplasma gondii tachyzoites on TGF-β mediated pathways in activated CD4+ T lymphocytes

Interference with transforming growth factor-β-mediated pathways helps several parasites to survive for long periods in immunocompetent hosts. Macrophages and dendritic cells infected by Toxoplasma, Leishmania and Plasmodium spp. produce large amounts of transforming growth factor-β and induce the differentiation of antigen-specific T-regulatory cells. Mechanisms not mediated by antigen-presentation could also account for the expansion of T-regulatory cells in parasitic diseases and they also might be mediated through transforming growth factor-β-receptor activated pathways. We explored the properties of soluble extracts from Leishmania infantum promastigotes, Toxoplasma gondii tachyzoites, Trichinella spiralis muscle larvae to expand the pool of T-regulatory cells in a population of polyclonally activated T cells in the absence of accessory cells, and compared their effects to those induced by Plasmodium falciparum extracts. Similarly to P. falciparum, L. infantum extracts activate the latent soluble form of transforming growth factor-β and that bound to the membrane of activated T lymphocytes. The interaction of the active cytokine with transforming growth factor-β receptor induces Foxp3 expression by activated lymphocytes, favoring their conversion through the T-regulatory phenotype. Both Toxoplasma gondii and L. infantum extracts are able to induce transforming growth factor-β production by activated T cells in the absence of accessory cells.

CX3CR1(+) B cells show immune suppressor properties

The immune regulatory functions of B cells are not fully understood yet. The present study aims to characterize a subtype of B cells that expresses CX3CR1. In this study, peripheral blood samples were collected from patients with food allergies and healthy subjects. Peripheral B cells were analyzed by flow cytometry. T cell proliferation was assessed by carboxyfluorescein succinimidyl ester dilution assay. The results showed that the CX3CR1(+) B cells were detected in the peripheral blood samples of healthy subjects and were significantly less in patients with food allergies. CX3CR1(+) B cells expressed high levels of TGF-β and integrin αvβ6. CX3CR1(+) B cells could efficiently suppress other effector CD4(+) T cell activation. We conclude that human peripheral CX3CR1(+) B cells have immune suppressor properties.

Functions of invariant NK T cells are modulated by TLR ligands and IFN-α

Invariant NK T (iNKT) cells perform numerous immunoregulatory functions. In mice, they express a unique and invariant Vα14-Jα18 rearrangement of α chain in their TCR recognizing glycolipid Ags presented by CD1d. This recognition results in the rapid release of both Th1- and Th2-type cytokines, making them early mediators of the immune response. Owing to their rapid activation and genetic rigidity of their TCR, iNKT cells share characteristics with innate lymphocytes. Therefore, we investigated whether iNKT cells could be induced to express TLRs, a class of pathogen recognition receptor. Mouse iNKT cells were stimulated with anti-CD3 monoclonal Ab and IFN-α, resulting in an increase in the transcription of TLRs 3, 5, 7 and 9, and increased surface expression of TLR3. These cells were subsequently stimulated with TLR ligands, resulting in an increase in the production of IFN-γ, IL-4 and TNF-α. Supernatants from these cells also increased macrophage production of IL-6 and prostaglandin E2, and increased their phagocytic activity and CD80 expression. These supernatants also reduced vesicular stomatitis virus-GFP replication in fibroblasts. This study demonstrates the role of IFN-α in iNKT cell activation, as well as the direct modulatory effects of TLR ligands on iNKT cell function, including antiviral activity.

Phenotype and regulation of immunosuppressive Vδ2-expressing γδ T cells

The proliferation and interleukin-2 production of CD4(+)CD25(-) αβ T cells were inhibited in a cell-contact manner by Vδ2 γδ T cells. The transcription factor Helios was constitutively expressed in about one-third of circulating γδ T cells and was upregulated by CD28-signaling. Our data suggest that Helios could serve as a marker for differential activation status rather than for regulatory T cells (Treg). Our findings also indicate that the interaction of CD86 on activated Vδ2 T cells and cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) on activated αβ T cells mediated the suppression because the suppressive effect was abolished by blocking the CD86:CTLA-4 interaction. Pre-treatment of Vδ2 T cells with Toll-like receptor 2 ligands enhanced phosphorylation of MAPKs, Akt, and NF-κB and partially abrogated the suppressive capacity, whereas on co-cultured responder T cells inhibitory molecules were downregulated and Akt and NF-κB phosphorylation was restored. Our results suggest that the regulation of αβ T cell proliferation by activated Vδ2 T cells might contribute to fine-tuning of αβ T cell responses.

Alterations in TLRs as new molecular markers of congenital infections with Human cytomegalovirus?

Toll-like receptors (TLRs) play a crucial role in non-specific immunity against various infections. The most common intrauterine infection, caused by Human cytomegalovirus (HCMV), results in perinatal morbidity and mortality of primary infected fetuses. The induction of immune response by TLRs was observed in HCMV infections in murine models and cell lines cultured in vitro. Studies reported an immunological response in pregnant women with primary HCMV infection and TLR2 activity in collecting of HCMV particles in placental syncytiotrophoblasts (STs) in vivo and cultured ST, and in stimulation of tumor necrosis factor (TNF)-α expression and damage of villous trophoblast. Expression levels of TLRs are associated with cell type, stage of pregnancy and response to microorganisms. We show the effect of HCMV infection on the development of pregnancy as well as the effect of TLR single-nucleotide polymorphisms on the occurrence and course of infectious diseases, immune response and diseases of pregnancy. We report the impact of TLRs on the function of miRNAs and the altered expression levels of these molecules, as observed in HCMV infections. We suggest that the methylation status of TLR gene promoter regions as epigenetic modifications may be significant in the immune response to HCMV infections. We conclude that it is important to study in detail the molecular mechanisms of TLR function in the immune response to HCMV infections in pregnancy.

Bacterial flagellin and diphtheria toxin co-stimulate IL-17-producing thymocytes

IL-17-producing thymocytes have been recently described and are believed to play a role as an immune cell population which is able to react against microbial components rapidly. For this reason, we here investigated the ability of two microbial stimulants, bacterial flagellin (a ligand for TLR5) and diphtheria toxin from Corynebacterium diphtheriae, to activate or co-activate (together with α-CD3 stimulation) thymocyte cytokine production. We find that both bacterial molecules do not induce cytokine-production by themselves, but co-activate IL-17-producing thymocytes together with α-CD3. Since diphtheria toxin is unlikely to affect mouse cells through the same mechanism as the lethal effect on human cells, our results point to an additional mechanism of diphtheria toxin to act on immune cells. However, there is no additive or super-additive effect after stimulation with diphtheria toxin combined with flagellin and α-CD3 co-activation, which suggests that microbial stimuli used in this study can only activate a limited number of IL-17 producing thymocytes.

Interrelationship of dendritic cells, type 1 interferon system, regulatory T cells and toll-like receptors and their role in lichen planus and lupus erythematosus -- a literature review

There is evidence that the activation of some receptors of the toll-like family (TLRs) of the innate immune system, and also changes in expression levels of forkhead box p3 (Foxp3) protein, which is found in regulatory T cells (Tregs), could be involved in the development of autoimmunity. We present here a literature review focusing on the interrelationship of dendritic cells, TLRs, Tregs and type 1 interferon in autoimmune diseases, with special interest in lichen planus and lupus erythematosus. Understanding the specific role of each of these factors would help elucidate the obscure aetiology of such diseases and open new perspectives for their management and treatment.