Expression and function of Toll-like receptor on T cells

Mixed pathology as a rule, not exception: Time to reconsider disease nosology

Parkinson's disease is a progressive neurodegenerative disorder that is associated with motor and nonmotor symptoms. Accumulation of misfolded α-synuclein is considered a key pathological feature during disease initiation and progression. While clearly deemed a synucleinopathy, the development of amyloid-β plaques, tau-containing neurofibrillary tangles, and even TDP-43 protein inclusions occur within the nigrostriatal system and in other brain regions. In addition, inflammatory responses, manifested by glial reactivity, T-cell infiltration, and increased expression of inflammatory cytokines, plus other toxic mediators derived from activated glial cells, are currently recognized as prominent drivers of Parkinson's disease pathology. However, copathologies have increasingly been recognized as the rule (>90%) and not the exception, with Parkinson's disease cases on average exhibiting three different copathologies. While microinfarcts, atherosclerosis, arteriolosclerosis, and cerebral amyloid angiopathy may have an impact on disease progression, α-synuclein, amyloid-β, and TDP-43 pathology do not seem to contribute to progression.

Higher Levels of Serum TLR2 and TLR4 in Patients with Hashimoto's Thyroiditis

OBJECTIVE

Hashimoto's thyroiditis (HT) is an autoimmune disorder caused by the interaction between genes and environmental triggers. HT is the most common endocrine disorder, as well as the most common cause of hypothyroidism. Autoimmunity plays a crucial role in the pathogenesis of HT and recent studies suggest that Toll-like receptor (TLR) signals lead to increased inflammatory response. The aim of our study is to investigate whether TLR-2 and TLR-4 levels and gene polymorphisms contribute to the damaged immune response leading to HT.

METHODS

Using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method, single-nucleotide polymorphisms (SNPs) of TLR2 gene Arg677Trp, Arg753Gln, 196-174 del and TLR4 gene Asp299Gly, Thr399Ile were studied in 100 patients with HT and 100 healthy controls. Also, we investigated serum levels of TLR-2 and TLR-4 in the immunopathogenesis of HT. TLR-2 and TLR-4 serum levels were found to be significantly higher in HT patients than the control group. However, no statistical significance was found between patient and control groups in terms of genotype frequencies and allele frequency distribution of TLR2 gene Arg677Trp, Arg753Gln, 196-174 del and TLR4 gene Asp299Gly, Thr399Ile polymorphisms.

RESULT

TLR2 gene Arg677Trp, Arg753Gln, 196-174 del and TLR4 gene Asp299Gly, Thr399Ile polymorphism do not appear to have a role in the development of HT disease. However, in our study, serum levels of TLR-2 and TLR-4 were found to be higher in HT patients than control groups.

CONCLUSION

These findings suggest that TLR-2 and TLR-4 play an important role in the immunopathologic mechanism of disease by causing an increase in proinflammatory response.

The predictive role of toll-like receptor-4 genetic polymorphisms in susceptibility to and prognosis of prostatic hyperplasia

Objective(s):

This study was aimed to evaluate whether single nucleotide polymorphisms (SNPs) of TLR4 and common living habits of prostate hyperplasia (BPH) patients would affect the subjects’ risk and prognosis.

Materials and Methods:

We totally recruited 501 BPH patients and 964 healthy controls. The patients’ international prostate symptom score (IPSS) and quality of life assessment (QoL) were designated as the prognostic indexes for BPH patients. Altogether 7 SNPs within TLR4 were selected, and the interactions among SNPs and living habits were explained with multi-factor dimensionality reduction (MDR) modeling.

Results:

The mutant alleles of rs10983755 (G>A) and rs1927907 (G>A) tended to put on risk of BPH, yet the wide alleles of rs4986791 (C>T) and rs115336889 (G>C) were associated with incremental susceptibility to BPH (P<0.05). The rs10983755 (GA) and rs1927907 (GA) were suggested as the marker of non-aggressive BPH, whereas rs4986791 (TT) could symbolize aggressive BPH (P<0.05). The homozygotes of rs4986791 (TT) and rs115336889 (CC) could improve the IPSS change, and rs115336889 (CC) was also correlated with more obviously ameliorated Qol change (P<0.05). Finally, MDR modeling suggested that rs4986791 (TT) and rs115336889 (GG) shaped the genotyping combination featured by the lowest risk of BPH when smoking or drinking history was also evaluated.

Conclusion:

The SNPs situated within TLR4 were potent candidates for predicting risk and prognosis of BPH patients, and their interactions within environmental parameters also helped to develop effective strategies for preventing and treating BPH.

Immunostimulatory Effect of Zanthoxylum schinifolium-Based Complex Oil Prepared by Supercritical Fluid Extraction in Splenocytes and Cyclophosphamide-Induced Immunosuppressed Rats

Complex oil of Zanthoxylum schinifolium and Perilla frutescens seed (ZPCO) is used as a traditional medicine due to its pharmacological activities. The aim of this study was to investigate the immunostimulatory effect of ZPCO in isolated splenocytes as well as in an immunosuppressed rat model, which was generated via oral administration of cyclophosphamide. Notably, our results showed that ZPCO exerted an immunity-enhancing effect both in vitro and in vivo. Specifically, ZPCO treatment enhanced the viability and inflammatory cytokine production of splenocytes and NK cell activity in vitro. Moreover, this product improved host defense under immunosuppressive conditions by increasing the number of immune cells and promoting the expression of cytokines involved in immune responses. Our results suggest that complex oil including Z. schinifolium should be explored as a novel immunostimulatory agent that could potentially be used for therapeutic purposes or as an ingredient in functional foods.

Basophils activated via TLR signaling may contribute to pathophysiology of type 1 autoimmune pancreatitis

BACKGROUND

Pathophysiology of type 1 autoimmune pancreatitis (AIP) is still unclear. We previously reported that M2 macrophages might play an important role in type 1 AIP. Recently, it has been reported that basophils regulate differentiation to M2 macrophages. In this study, we investigated basophils from the pancreatic tissue and peripheral blood of individuals with type 1 AIP.

METHODS

By using immunohistochemistry, we investigated basophils in pancreatic tissue from 13 patients with type 1 AIP and examined expression of toll-like receptors (TLRs) by these cells. Additionally, we obtained peripheral blood samples from 27 healthy subjects, 40 patients with type 1 AIP, 8 patients with alcoholic chronic pancreatitis, 10 patients with bronchial asthma, and 10 patients with atopic dermatitis, and analyzed activation of basophils by stimulating them with ligands of TLR1-9. We also compared TLR expression in basophils from the tissue and blood samples.

RESULTS

Basophils were detected in pancreatic tissues from 10 of 13 patients with type 1 AIP. Flow cytometric analysis revealed that the ratios of basophils activated by TLR4 stimulation in type 1 AIP (9.875 ± 1.148%) and atopic dermatitis (11.768 ± 1.899%) were significantly higher than those in healthy subjects (5.051 ± 0.730%; P < 0.05). Levels of basophils activated by TLR2 stimulation were higher in seven type 1 AIP cases. Furthermore, stimulation of TLR2 and/or TLR4, which were expressed by basophils in pancreas, activated basophils in peripheral blood.

CONCLUSIONS

Basophils activated via TLR signaling may play an important role in the pathophysiology of type 1 AIP.

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.

Modulation of LPS-induced CD4+ T-cell activation and apoptosis by antioxidants in untreated asymptomatic HIV infected participants: an in vitro study

Persistent immune activation characterises HIV infection and is associated with depletion of CD4+ T-cells and increased risk of disease progression. Early loss of gut mucosal integrity results in the translocation of microbial products such as lipopolysaccharide (LPS) into the systemic circulation. This is an important source of on-going immune stimulation. The purpose of this study was to determine levels of CD4+ T-cell activation (%CD25 expression) and apoptosis (% annexin V/7-AAD) in asymptomatic, untreated HIV infection at baseline and after stimulation with LPS and incubation with or without vitamin C and N-acetylcysteine. LPS induced a significant (P < 0.03) increase in %CD25 expression, annexin V, and 7-AAD in HIV positive individuals. NAC in combination with vitamin C, significantly (P = 0.0018) reduced activation and early apoptosis of CD4+ T-cells to a greater degree than with either antioxidant alone. Certain combinations of antioxidants could be important in reducing the harmful effects of chronic immune activation and thereby limit CD4+ T-cell depletion. Importantly, we showed that CD4+ T-cells of the HIV positive group responded better to a combination of the antioxidants at this stage than those of the controls. Therefore, appropriate intervention at this asymptomatic stage could rescue the cells before repetitive activation results in the death of CD4+ T-cells.

Antigen-free adjuvant assists late effector CD4 T cells to transit to memory in lymphopenic hosts

The events controlling the transition of T cells from effector to memory remain largely undefined. Many models have been put forth to account for the origin of memory precursors, but for CD4 T cells initial studies reported that memory T cells derive from IFN-γ-nonproducing effectors, whereas others suggested that memory emanates from highly activated IFN-γ-producing effectors. In this study, using cell proliferation, expression of activation markers, and production of IFN-γ as a measure of activation, we defined two types of effector CD4 T cells and investigated memory generation. The moderately activated early effectors readily transit to memory, whereas the highly activated late effectors, regardless of their IFN-γ production, develop minimal memory. Boosting with Ag-free adjuvant, however, rescues late effectors from cell death and sustains both survival and IFN-γ cytokine responses in lymphopenic hosts. The adjuvant-mediated memory transition of late effectors involves the function of TLRs, most notably TLR9. These findings uncover the mechanism by which late effector CD4 T cells are driven to transit to memory and suggest that timely boosts with adjuvant may enhance vaccine efficacy.

Pam3CSK(4) enhanced beta cell loss and diabetogenesis: the roles of IFN-gamma and IL-17

Toll like receptors are primary sensors of both innate and adaptive immune systems. They activate APCs and influence T-cell function in inflammatory autoimmune response. Studies have shown that TLR manipulation may lead to either tolerance or trigger autoimmunity. Using diabetogenic and subdiabetogenic multiple low doses of streptozotocin, we demonstrate here that Pam3 CYS-CK4 a TLR-2 agonist, enhances and promotes diabetes in C57BL/6 male mice following increased apoptosis of β islet cells. FACS analysis of isolated pancreatic lymph node cells revealed significant increased number of macrophages, dendritic cells, CD4(+) TNF-α(+), CD4(+) IFN-γ(+) and most significantly, CD4(+) IL-17(+) and reduced number of CD25(+)Fox p3(+) T cells after Pam3CSK4 treatment. Genetic deletion of IFN-γ prevents whereas deletion of IL-17 reduced severity of Pam3CSK4-induced enhancement of diabetes. TLR-2 agonist-enhanced diabetogenesis is also influenced by enhanced influx of antigen presenting cells and suppression of regulatory T cell activity.

Toll-like receptors in human papillomavirus infection

Infection with human papillomaviruses (HPVs) often causes cutaneous benign lesions, cervical cancer, and a number of other tumors. The mechanisms of host immune system to prevent and control HPV infection still remain poorly understood. Toll-like receptors (TLRs) are specific pattern recognition molecules that bind to microbial components to trigger innate immunity and direct adaptive immunity in the face of immunological danger. TLRs have been established to play an essential role in sensing and initiating antiviral immune responses. Recent accumulating evidence demonstrated that HPVs modulate TLR expression and interfere with TLR signaling pathways, leading to persistent viral infection and carcinogenesis. This review summarizes current knowledge on the roles of TLR during HPV infection, focusing on TLR recognition, modulation of TLR expression and signaling, regulatory receptors involved in TLR signaling, and cross-talk of TLRs with antimicrobial peptides. Immunotherapeutic strategies based on TLR agonists have emerged to be one of the novel promising avenues in treatment of HPV-associated diseases in the future.

Activation of toll-like receptor 2 prevents suppression of T-cell interferon γ production by modulating p38/extracellular signal-regulated kinase pathways following alcohol and burn injury

Recent studies indicate that toll-like receptors (TLRs) are expressed on T cells and that these receptors directly or indirectly activate the adaptive immune system. We have shown previously that acute alcohol/ethanol (EtOH) intoxication combined with burn injury suppresses mesenteric lymph node (MLN) T-cell interleukin-2 (IL-2) and interferon γ (IFN-γ) production. We examined whether direct stimulation of T cells with TLR2, 4, 5 and 7 agonists modulates CD3-mediated T-cell IL-2/IFN-γ release following EtOH and burn injury. Male mice were gavaged with EtOH (2.9 gm/kg) 4 h prior to receiving an ~12.5% total body surface area sham or full-thickness burn injury. Animals were killed on d 1 after injury and T cells were purified from MLN and spleens. T cells were cultured with plate-bound anti-CD3 in the presence or absence of various TLR ligands. Although TLR2, 4 and 5 agonists potentiate anti-CD3-dependent IFN-γ by T cells, the TLR2 agonist alone induced IFN-γ production independent of CD3 stimulation. Furthermore, T cells were treated with inhibitors of myeloid differentiation primary response protein 88 (MyD88), TIR domain-containing adaptor protein (TIRAP), p38 and/or extracellular signal-regulated kinase (ERK) to determine the mechanism by which TLR2 mediates IL-2/IFN-γ production. IL-2 was not influenced by TLR agonists. MyD88 and TIRAP inhibitory peptides dose-dependently diminished the ability of T cells to release IFN-γ. p38 and ERK inhibitors also abolished TLR2-mediated T-cell IFN-γ. Together, our findings suggest that TLR2 directly modulates T-cell IFN-γ production following EtOH and burn injury, independent of antigen-presenting cells. Furthermore, we demonstrated that MyD88/TIRAP-dependent p38/ERK activation is critical to TLR2-mediated T-cell IFN-γ release following EtOH and burn injury.

Graft rejection - endogenous or allogeneic?

The presence and persistence of alloantigen is necessary for graft-specific T-cell-mediated immunity. However, specificity comprises only a single facet of an extremely complex process. Evidence is accruing to suggest that immunogenicity could be manipulated by endogenous ligands released during tissue injury. Stress molecules are significantly up-regulated following transplantation and stimulate conserved receptors on a range of leucocytes, including dendritic cells (DCs). The DCs are essential for co-stimulation and the induction of adaptive immunity. Stress signals can act as an adjuvant leading to DC maturation and activation. DCs stimulated by endogens exhibit enhanced alloantigen presentation, co-stimulation and production of pro-inflammatory cytokines, such as interleukin-1β (IL-1β) and IL-18. Inflammasomes have a major role in IL-1β/IL-18 production and secretion, and can be stimulated by endogens. Importantly, the polarization toward inflammatory T helper type 17 cells as opposed to regulatory T cells is dependent upon, among other factors, IL-1β. This highlights an important differentiation pathway that may be influenced by endogenous signals. Minimizing graft damage and stress expression should hypothetically be advantageous, and we feel that this area warrants further research, and may provide novel treatment modalities with potential clinical benefit.

Age and low levels of circulating vitamin D are associated with impaired innate immune function

This study investigated in vivo the influence of age and vitamin D status on innate immune function in HC. Serum 25OHD was measured in 71 HC. TLR expression on various subpopulations of PBMCs, as well as TLR function by stimulating PBMCs with specific ligands, was assessed by flow cytometry. Circulating cathelicidin levels were determined by ELISA. Serum 25OHD levels decreased with age, and there was a significant inverse correlation between 25OHD levels and age. There was a negative correlation between serum 25OHD levels and MFI expression of TLR7 on B cells, T cells, and monocytes. TLR7 function, addressed by in vitro stimulation with a specific agonist, was significantly correlated with serum 25OHD levels, and this was especially a result of the results in HC older than 60 years. MFI expression of TLR5 on T cells and TLR2 on monocytes was also negatively correlated with serum 25OHD levels. TLR1 (monocytes) and TLR2 (monocytes) expression was positively correlated with age. Furthermore, TLR4 and TLR8 function was negatively correlated with age. Circulating cathelicidin levels decreased with age and were positively correlated with 25OHD levels. Aging is accompanied by changes in expression and function of several TLRs. Serum 25OHD levels decrease with age and are also associated with a change in expression and defective function of certain TLRs, especially those involved in viral response.

Intracellular and extracellular cytokine-like functions of prothymosin α: implications for the development of immunotherapies

Prothymosin α (ProTα) is a 12.5-kDa, highly acidic protein widely distributed in different cell types expressed intracellularly and extracellularly. ProTα does not contain a secretion-signal sequence and is released by a nonclassical secretory pathway with a cargo protein. New findings on the extracellular function of ProTα have yielded exciting insights into the cytokine-like functions of this host protein that stimulates type I interferon via Toll-like receptor 4. Here, we discuss the intracellular function of ProTα, how new findings of cytokine-like activities of ProTα aid our understanding of mechanisms that direct ProTα functions, and the potential application of these new insights to the development of immunotherapies.

TLR2 activation enhances HIV nuclear import and infection through T cell activation-independent and -dependent pathways

TLR2 activation plays a crucial role in Neisseria gonorrheae-mediated enhancement of HIV infection of resting CD4(+) T cells. We examined signaling pathways involved in the HIV enhancing effect of TLR2. TLR2 but not IL-2 signals promoted HIV nuclear import; however, both signals were required for the maximal enhancing effect. Although TLR2 signaling could not activate T cells, it increased IL-2-induced T cell activation. Cyclosporin A and IkBα inhibitor blocked TLR2-mediated enhancement of HIV infection/nuclear import. PI3K inhibitor blocked HIV infection/nuclear import and T cell activation and exerted a moderate inhibitory effect on cell cycle progression in CD4(+) T cells activated by TLR2/IL-2. Blockade of p38 signaling suppressed TLR2-mediated enhancement of HIV nuclear import/infection. However, the p38 inhibitor did not have a significant effect on T cell activation or TCR/CD3-mediated enhancement of HIV infection/nuclear import. The cell cycle arresting reagent aphidicolin blocked TLR2- and TCR/CD3-induced HIV infection/nuclear import. Finally, cyclosporin A and IκBα and PI3K inhibitors but not the p38 inhibitor blocked TLR2-mediated IκBα phosphorylation. Our results suggest that TLR2 activation enhances HIV infection/nuclear import in resting CD4(+) T cells through both T cell activation-dependent and -independent mechanisms.

Fetal calf serum heat inactivation and lipopolysaccharide contamination influence the human T lymphoblast proteome and phosphoproteome

BACKGROUND

The effects of fetal calf serum (FCS) heat inactivation and bacterial lipopolysaccharide (LPS) contamination on cell physiology have been studied, but their effect on the proteome of cultured cells has yet to be described. This study was undertaken to investigate the effects of heat inactivation of FCS and LPS contamination on the human T lymphoblast proteome. Human T lymphoblastic leukaemia (CCRF-CEM) cells were grown in FCS, either non-heated, or heat inactivated, having low (< 1 EU/mL) or regular (< 30 EU/mL) LPS concentrations. Protein lysates were resolved by 2-DE followed by phospho-specific and silver nitrate staining. Differentially regulated spots were identified by nano LC ESI Q-TOF MS/MS analysis.

RESULTS

A total of four proteins (EIF3M, PRS7, PSB4, and SNAPA) were up-regulated when CCRF-CEM cells were grown in media supplemented with heat inactivated FCS (HE) as compared to cells grown in media with non-heated FCS (NHE). Six proteins (TCPD, ACTA, NACA, TCTP, ACTB, and ICLN) displayed a differential phosphorylation pattern between the NHE and HE groups. Compared to the low concentration LPS group, regular levels of LPS resulted in the up-regulation of three proteins (SYBF, QCR1, and SUCB1).

CONCLUSION

The present study provides new information regarding the effect of FCS heat inactivation and change in FCS-LPS concentration on cellular protein expression, and post-translational modification in human T lymphoblasts. Both heat inactivation and LPS contamination of FCS were shown to modulate the expression and phosphorylation of proteins involved in basic cellular functions, such as protein synthesis, cytoskeleton stability, oxidative stress regulation and apoptosis. Hence, the study emphasizes the need to consider both heat inactivation and LPS contamination of FCS as factors that can influence the T lymphoblast proteome.

Role of TLR4 and TCR or BCR against baicalin-induced responses in T and B cells

Baicalin (BA), a flavonoid compound isolated from Scutellaria baicalensis, has been shown to possess a number of pharmacological effects including antiviral, anti-inflammatory, antioxidant and immune regulation. Here, we examined its effects on human T and B cells proliferation by MTT assay and found that BA stimulated T and B cells proliferation, independently and cooperatively with Con-A (T cells) or LPS (B cells). Then, we analyzed the effects of BA treatment on the mRNA expression of Toll-like receptors (TLRs), IL-2, IFN-γ and IL-12 in T and B cells by real-time RT-PCR and attempted to observe whether blocking TLR4 had influence on mRNA expression. We found that BA treatment significantly up-regulated TLR3, 7, 8 and 9 mRNA expressions in T and B cells, IL-2 and IFN-γ in T cells and IL-12 in B cells. The increased mRNA expressions were suppressed after blocking TLR4. We further analyzed the effects of BA treatment on TCR vβ and CD79 mRNA expression levels in T and B cells and explored whether blocking TCR (αβ) or BCR mIgM F(ab')(2) had an influence on mRNA expression. We found that BA treatment significantly improved TCR vβ and CD79 mRNA expression in T and B cells, respectively, and the improvements were all inhibited after blocking TCR (αβ) or BCR mIgM F(ab')(2). Our results suggested that BA participates in innate and adaptive immune regulation by up-regulating the mRNA expression of TLRs (3, 7, 8 and 9), IL-2, IFN-γ and IL-12 in T and B cells, which is mediated by TLR4, and by improving the mRNA expression of TCR vβ and CD79, which is mediated by TCR (αβ) and BCR mIgM, respectively. Therefore, TLR4, TCR (αβ) and BCR mIgM are all the immune receptors for BA on T and B cells.

Triggering of toll-like receptor signaling pathways in T cells contributes to the anti-tumor efficacy of T cell responses

Traditionally, expression of toll-like receptors (TLRs) has been associated with innate immune cells in particular professional antigen presenting cells and natural killer cells. This led to the concept that the adjuvant effects of ligation of TLR in a host occur mainly in innate immune cells. However, this concept has been challenged by recent studies including ours demonstrating that T cells express appreciated levels of different TLRs, which can serve as costimulatory co-receptors during polyclonal and antigen-specific stimulation of T cells. Because T cells express low levels of TLRs as compared to innate immune cells, increasing the expression levels of TLRs in T cells can significantly maximize their responses to the costimulatory effects of TLR ligation. This review article focuses on the potential role of TLR expression in T cells in their responses to vaccination regimen containing TLR agonists and how it can be modulated to optimize anti-tumor immunity.

Toll-like receptor 4 is involved in human and mouse vein graft remodeling, and local gene silencing reduces vein graft disease in hypercholesterolemic APOE*3Leiden mice

OBJECTIVE

The goal of this study was to explore the role of Toll-like receptor 4 (TLR4) in vein graft remodeling and disease.

METHODS AND RESULTS

First, expression of TLR4 was analyzed in freshly isolated human saphenous veins (huSV), in freshly isolated huSV ex vivo perfused in an extracorporeal circulation, or in huSV used as coronary vein grafts. Marked induction of focal TLR4 expression was observed in perfused fresh huSV. Moreover, TLR4 was abundantly present in lesions in fresh huSV or in intimal hyperplasia in coronary vein grafts. Second, mouse venous bypass grafting was performed. In grafts of hypercholesterolemic APOE*3Leiden mice, increased TLR4 mRNA and protein was detected over time by reverse transcription-polymerase chain reaction and immunohistochemistry. Furthermore, the local presence of the endogenous TLR4 ligands heat shock protein 60, high-mobility group box 1, tenascin-C, and biglycan in the grafts was demonstrated. TLR4 deficiency in C3H-Tlr4LPS-d (LPS indicates lipopolysaccharide) mice resulted in 48±12% less vein graft wall thickening (P=0.04) than in Balb/c controls. Moreover, local TLR4 gene silencing in hypercholesterolemic APOE*3Leiden mice using lentiviral short hairpin RNA against TLR4 administered perivascularly around vein grafts led to a 44±13% reduction of vessel wall thickening compared with controls (P=0.0059).

CONCLUSIONS

These results indicate that TLR4 is involved in vein graft remodeling and can be used as a local therapeutic target against vein graft disease.

Cell-to-cell transmission of retroviruses: Innate immunity and interferon-induced restriction factors

It has been known for some time that retroviruses can disseminate between immune cells either by conventional cell-free transmission or by directed cell-to-cell spread. Over the past few years there has been increasing interest in how retroviruses may use cell-to-cell spread to promote more rapid infection kinetics and circumvent humoral immunity. Effective humoral immune responses are intimately linked with innate immunity and the interplay between retroviruses and innate immunity is a rapidly expanding area of research that has been advanced considerably by the identification of cellular restriction factors that provide barriers to retroviral infection. The effect of innate immunity and restriction factors on retroviral cell-to-cell spread has been comparatively little studied; however recent work suggests this maybe changing. Here I will review some recent advances in what is a budding area of retroviral research.

Chronic stress promotes lymphocyte reduction through TLR2 mediated PI3K signaling in a β-arrestin 2 dependent manner

Physical and psychological stress can alter the immune system in both humans and animals. Stress is a known risk factor for numerous human diseases, such as infectious and autoimmune diseases, and cancer. Toll-like receptors (TLRs) play a pivotal role in the induction of innate and adaptive immune response. Our previous studies have shown that TLR4 deficiency prevents stress-induced splenocyte reduction. However, the role of TLR2 in stress-mediated lymphocyte reduction is unknown. In this study, we investigated the effects of TLR2 ligands on stress-induced lymphocyte reduction. We also defined whether the phosphoinositide 3-kinases (PI3Ks)/Akt pathway contributes to TLR2-mediated lymphocyte numbers altered by stress. Our data have shown that stimulation of TLR2 by TLR2 ligands peptidoglycan (PGN) or Pam3CSK4 (Pam3) attenuates stress-induced reduction in lymphocyte numbers. However, TLR2 ligand-induced protection from stress-induced lymphocyte reduction is lost in TLR2 deficiency in mice. Furthermore, stimulation of TLR2 by PGN induces protection from stress-induced reduction in the number of splenocytes through PI3K. Moreover, PGN dramatically increases the level of phosphorylation of Akt through a PI3K-dependent manner. Moreover, we found that stimulation of TLR2 by PGN induced protection from stress-induced reduction in splenocyte numbers is abolished in β-arrestin 2 deficient mice. In addition, PGN-induced immune protection in stress-induced changes of cytokine levels appears to require β-arrestin 2, a multifunctional adaptor and signal transducer. Collectively, our study thus demonstrates that stimulation of TLR2-mediated PI3K signaling attenuates splenocyte reduction induced by stress, and that β-arrestin 2 modulates TLR2-mediated immune response following stress.

Neural injury following stroke: are Toll-like receptors the link between the immune system and the CNS?

The CNS can exhibit features of inflammation in response to injury, infection or disease, whereby resident cells generate inflammatory mediators, including cytokines, prostaglandins, free radicals and complement, chemokines and adhesion molecules that recruit immune cells, and activate glia and microglia. Cerebral ischaemia triggers acute inflammation, which exacerbates primary brain damage. The regulation of inflammation after stroke is multifaceted and comprises vascular effects, distinct cellular responses, apoptosis and chemotaxis. There are many cell types that are affected including neurons, astrocytes, microglia and endothelial cells, all responding to the resultant neuroinflammation in different ways. Over the past 20 years, researchers examining brain tissue at various time intervals after stroke observed the presence of inflammatory cells, neutrophils and monocytes at the site of injury, as well as the activation of endogenous glia and microglia. This review examines the involvement of these cells in the progression of neural injury and proposes that the Toll-like receptors (TLRs) are likely to be an integral component in the communication between the CNS and the periphery. This receptor system is the archetypal pathogen sensing receptor system and its presence and signalling in the brain following neural injury suggests a more diverse role. We propose that the TLR system presents excellent pharmacological targets for the design of a new generation of therapeutic agents to modulate the inflammation that accompanies neural injury.

Superantigen-induced proliferation of human CD4+CD25- T cells is followed by a switch to a functional regulatory phenotype

Bacterial superantigens are potent T cell activators. In humans they cause toxic shock and scarlet fever, and they are implicated in Kawasaki's disease, autoimmunity, atopy, and sepsis. Their function remains unknown, but it may be to impair host immune responses increasing bacterial carriage and transmission. Regulatory (CD25(+)FOXP3(+)) T cells (Tregs) play a role in controlling inflammatory responses to infection. Approximately 2% of circulating T cells are naturally occurring Tregs (nTregs). Conventional Ag stimulation of naive FOXP3(-) T cells induces Ag-specific Tregs. Polyclonal T cell activation has been shown to produce non-Ag-specific Tregs. Because superantigens are unique among microbial virulence factors in their ability to trigger polyclonal T cell activation, we wanted to determine whether superantigen stimulation of T cells could induce non-Ag-specific Tregs. We assessed the effect of superantigen stimulation of human T cells on activation, regulatory markers, and cytokine production by flow cytometry and T cell suppression assays. Stimulation of PBMCs with staphylococcal exotoxin A and streptococcal pyrogenic exotoxins A and K/L resulted in dose-dependent FOXP3 expression. Characterization of this response for streptococcal pyrogenic exotoxin K/L confirmed its Vβ specificity, that CD25(+)FOXP3(+) cells arose from CD25(-) T cells and required APCs. These cells had increased CTLA-4 and CD127 expression, typical of the recently described activated converted Treg-like cells, and exhibited functional suppressor activity comparable to nTregs. Superantigen-stimulated CD25(+)FOXP3(+) T cells expressed IL-10 at lower superantigen concentrations than was required to trigger IFN-γ production. This study provides a mechanism for bacterial evasion of the immune response through the superantigen induction of Tregs.

Differential expression of Toll-like receptors in follicular lymphoma, diffuse large B-cell lymphoma and peripheral T-cell lymphoma

Although Toll-like receptors (TLRs) in mammals are well-known to play important roles in innate immunity, newer roles for the TLRs have suggested that cells with aberrant TLR expression may have a survival advantage over normal cells. Lymphocytes are one of a small number of cell types that express many of the TLRs, suggesting that abnormal TLR levels/signaling may potentially influence the progression of malignant lymphomas. Thus, frozen samples of 51 lymph nodes from patients with follicular lymphoma (FL), diffuse large B-cell lymphoma (DLBCL) and peripheral T-cell lymphoma (PTCL) were analyzed for the expression of TLR1 to 9 using quantitative real-time PCR, and compared to those in reactive lymphadenopathy (RL) samples. TLR2 was over-expressed in both DLBCL and PTCL but not in FL when compared to RL. TLR1 and TLR4 expression was up-regulated in PTCL, while TLR8 was highly expressed in DLBCL. Although TLR5 showed lower expression in FL, expression of TLR3, TLR6, TLR7 and TLR9 did not vary significantly between different lymphoma subtypes. Double immunostaining revealed an increase in the number of TLR2 and/or TLR8 expressing lymphoma cells in DLBCL. In PTCL, TLR2 and TLR4 expression was localized to neoplastic T cells. TLR expression is highly variable among lymphoma subtypes. However, despite this some significant differences exist that may prove useful in the development of novel therapeutic strategies.

Innate immune recognition and activation during HIV infection

The pathogenesis of HIV infection, and in particular the development of immunodeficiency, remains incompletely understood. Whichever intricate molecular mechanisms are at play between HIV and the host, it is evident that the organism is incapable of restricting and eradicating the invading pathogen. Both innate and adaptive immune responses are raised, but they appear to be insufficient or too late to eliminate the virus. Moreover, the picture is complicated by the fact that the very same cells and responses aimed at eliminating the virus seem to play deleterious roles by driving ongoing immune activation and progressive immunodeficiency. Whereas much knowledge exists on the role of adaptive immunity during HIV infection, it has only recently been appreciated that the innate immune response also plays an important part in HIV pathogenesis. In this review, we present current knowledge on innate immune recognition and activation during HIV infection based on studies in cell culture, non-human primates, and HIV-infected individuals, and discuss the implications for the understanding of HIV immunopathogenesis.

Toll-like receptor (TLR) expression on CD4+ and CD8+ T-cells in patients chronically infected with hepatitis C virus

Toll-like receptor (TLR) expression on T-cells and the signalling pathways that lead to the production of cytokines may limit antigen-specific T-cell responses. Here, expression of TLR and retinoic acid inducible gene I (RIG-I) on T-cells were evaluated in patients chronically infected with hepatitis C virus (HCV), before and during pegylated interferon-alpha and ribavirin therapy. Expression of TLR2,3,4,7,9 and retinoic acid inducible gene (RIG)-I on different CD4(+) and CD8(+) T-cell sub-populations (naïve: CD45RA(+)CD57(-); central memory: T(CM) CD45RA(-)CD57(-); effector memory: T(EM) CD45RA(-)CD57(+) and terminally differentiated effector memory: T(EMRA) CD45RA(+)CD57(+)) were measured by flow cytometry. TLR7, TLR9 and RIG-I expression on CD4(+) T-cells and RIG-I expression on CD8(+) T-cells was higher in patients than healthy controls. Therapy increased expression of TLR2, TLR4 and TLR9 and this was observed for all T-cell sub-populations. Evaluation of TLR expression at baseline did not identify patients able to achieve sustained virological response following therapy.

TLR2 engagement on dendritic cells promotes high frequency effector and memory CD4 T cell responses

Ligation of TLR by distinct pathogen components provides essential signals for T cell priming, although how individual TLR engagement affects primary and memory T cell responses is not well defined. In this study, we demonstrate distinct effects of TLR2 vs TLR4 engagement on primary and memory CD4 T cell responses due to differential effects on APC. Priming of influenza hemagglutinin (HA)-specific naive CD4 T cells with HA peptide and the TLR2 agonist Pam3CysK in vivo resulted in a high frequency of activated HA-specific CD4 T cells that predominantly produced IL-2 and IL-17, whereas priming with HA peptide and the TLR4 agonist LPS yielded a lower frequency of HA-specific CD4 T cells and predominant IFN-gamma producers. TLR2 agonist priming depended on TLR2 expression by APC, as wild-type CD4 T cells did not expand in response to peptide and Pam3CysK in TLR2-deficient hosts. TLR2-mediated priming also led to an increased frequency of Ag-specific memory CD4 T cells compared with TLR4 priming and mediated enhanced secondary responses to influenza challenge. Our results show that TLR engagement on APC influences both primary and secondary CD4 T cell responses, and suggest that long-term functional capacities of T cells are set by innate signals during early phases of an infection.

Neisseria gonorrhoeae enhances HIV-1 infection of primary resting CD4+ T cells through TLR2 activation

Sexually transmitted infections increase the likelihood of HIV-1 transmission. We investigated the effect of Neisseria gonorrheae (gonococcus [GC]) exposure on HIV replication in primary resting CD4(+) T cells, a major HIV target cell during the early stage of sexual transmission of HIV. GC and TLR2 agonists, such as peptidylglycan (PGN), Pam(3)CSK(4), and Pam(3)C-Lip, a GC-derived synthetic lipopeptide, but not TLR4 agonists including LPS or GC lipooligosaccharide enhanced HIV-1 infection of primary resting CD4(+) T cells after viral entry. Pretreatment of CD4(+) cells with PGN also promoted HIV infection. Anti-TLR2 Abs abolished the HIV enhancing effect of GC and Pam(3)C-Lip, indicating that GC-mediated enhancement of HIV infection of resting CD4(+) T cells was through TLR2. IL-2 was required for TLR2-mediated HIV enhancement. PGN and GC induced cell surface expression of T cell activation markers and HIV coreceptors, CCR5 and CXCR4. The maximal postentry HIV enhancing effect was achieved when PGN was added immediately after viral exposure. Kinetic studies and analysis of HIV DNA products indicated that GC exposure and TLR2 activation enhanced HIV infection at the step of nuclear import. We conclude that GC enhanced HIV infection of primary resting CD4(+) T cells through TLR2 activation, which both increased the susceptibility of primary CD4(+) T cells to HIV infection as well as enhanced HIV-infected CD4(+) T cells at the early stage of HIV life cycle after entry. This study provides a molecular mechanism by which nonulcerative sexually transmitted infections mediate enhancement of HIV infection and has implication for HIV prevention and therapeutics.

Differential expression of Toll-like receptors on human alveolar macrophages and autologous peripheral monocytes

BACKGROUND

Toll-like receptors (TLRs) are critical components in the regulation of pulmonary immune responses and the recognition of respiratory pathogens such as Mycobacterium Tuberculosis (M.tb). Through examination of human alveolar macrophages this study attempts to better define the expression profiles of TLR2, TLR4 and TLR9 in the human lung compartment which are as yet still poorly defined.

METHODS

Sixteen healthy subjects underwent venipuncture, and eleven subjects underwent additional bronchoalveolar lavage to obtain peripheral blood mononuclear and bronchoalveolar cells, respectively. Surface and intracellular expression of TLRs was assessed by fluorescence-activated cell sorting and qRT-PCR. Cells were stimulated with TLR-specific ligands and cytokine production assessed by ELISA and cytokine bead array.

RESULTS

Surface expression of TLR2 was significantly lower on alveolar macrophages than on blood monocytes (1.2 +/- 0.4% vs. 57 +/- 11.1%, relative mean fluorescence intensity [rMFI]: 0.9 +/- 0.1 vs. 3.2 +/- 0.1, p < 0.05). The proportion of TLR4 and TLR9-expressing cells and the rMFIs of TLR4 were comparable between alveolar macrophages and monocytes. The surface expression of TLR9 however, was higher on alveolar macrophages than on monocytes (rMFI, 218.4 +/- 187.3 vs. 4.4 +/- 1.4, p < 0.05) while the intracellular expression of the receptor and the proportion of TLR9 positive cells were similar in both cell types. TLR2, TLR4 and TLR9 mRNA expression was lower in bronchoalveolar cells than in monocytes.Pam3Cys, LPS, and M.tb DNA upregulated TLR2, TLR4 and TLR9 mRNA in both, bronchoalveolar cells and monocytes. Corresponding with the reduced surface and mRNA expression of TLR2, Pam3Cys induced lower production of TNF-alpha, IL-1beta and IL-6 in bronchoalveolar cells than in monocytes. Despite comparable expression of TLR4 on both cell types, LPS induced higher levels of IL-10 in monocytes than in alveolar macrophages. M.tb DNA, the ligand for TLR9, induced similar levels of cytokines in both cell types.

CONCLUSION

The TLR expression profile of autologous human alveolar macrophages and monocytes is not identical, therefore perhaps contributing to compartmentalized immune responses in the lungs and systemically. These dissimilarities may have important implications for the design and efficacy evaluation of vaccines with TLR-stimulating adjuvants that target the respiratory tract.

Intestinal bacteria and the regulation of immune cell homeostasis

The human intestine is colonized by an estimated 100 trillion bacteria. Some of these bacteria are essential for normal physiology, whereas others have been implicated in the pathogenesis of multiple inflammatory diseases including IBD and asthma. This review examines the influence of signals from intestinal bacteria on the homeostasis of the mammalian immune system in the context of health and disease. We review the bacterial composition of the mammalian intestine, known bacterial-derived immunoregulatory molecules, and the mammalian innate immune receptors that recognize them. We discuss the influence of bacterial-derived signals on immune cell function and the mechanisms by which these signals modulate the development and progression of inflammatory disease. We conclude with an examination of successes and future challenges in using bacterial communities or their products in the prevention or treatment of human disease.

Pattern recognition by Toll-like receptors

The mammalian immune system senses pathogens through pattern recognition receptors and responds with activation. The Toll-like receptors (TLRs) that are expressed on antigen presenting cells such as macrophages and dendritic cells play a critical role in this process. Their signaling activates these cells and leads to an innate immune response with subsequent initiation of an adaptive immune response. Each TLR recognizes specific structures and induces common inflammatory cytokines. However, some TLRs have specific functions, such as induction of Type I interferons. The TLR dependent cytokine response is reflected in the induction of common and specific signaling pathways leading to adequate immune responses for different pathogens. Some TLRs are also activated by endogenous structures that are released during infection, but these structures may promote or sustain autoimmune diseases under certain circumstances. In addition, TLRs directly shape adaptive immune responses of T and B cells and play an important role in homeostasis of gut epithelium and lung repair after injury.

Transepithelial activation of human leukocytes by probiotics and commensal bacteria: role of Enterobacteriaceae-type endotoxin

The goal of the current study was to clarify whether commercially available probiotics induce greater trans-epithelial activation of human leukocytes than do commensal, food-derived and pathogenic bacteria and to identify the compounds responsible for this activation. Eleven different bacterial strains, and some of their pathogen-associated molecular patterns, were incubated apically on a confluent layer of intestinal epithelial cells (Caco-2), which were basolaterally co-cultured with human mononuclear leukocytes. Only Gram-negative bacteria having Enterobacteriaceae-type endotoxin (commensal Escherichia coli K12, probiotic E. coli Nissle, EPEC) induced basolateral production of TNF-alpha, IFN-gamma, IL 6, 8, and 10. Gram-positive probiotics (Lactobacillus spp. and Bifidobacterium spp.) had virtually no effect. In addition, commensals (Enterococcus faecalis, Bacteroides vulgatus) and food fermenters (Lactobacillus spp.) did not stimulate leukocytes transepithelially. Endotoxin from E. coli and Salmonella enterica Typhimurium induced comparable transepithelial stimulation of leukocytes, but not endotoxin from B. vulgatus or lipoteichoic acid from E. faecalis. Endotoxin-binding agents (polymyxin, colistin) completely abrogated transepithelial activation of leukocytes. Enterobacteriaceae-type endotoxin is a crucial factor in transepithelial stimulation of leukocytes, regardless of whether it is produced by probiotics or other bacteria. Hence, transepithelial stimulation ofleukocytes' innate immune response seems to not be linked to the health-promoting effects ofprobiotics.

Porin of Shigella dysenteriae directly promotes toll-like receptor 2-mediated CD4+ T cell survival and effector function

Porin of Shigella dysenteriae type 1 up-regulated Toll-like receptor (TLR)2 on CD3-stimulated CD4(+) T cells but could not induce the expression of other TLRs. TLR2 in association with myeloid differentiating factor 88 (MyD88) triggered the downstream signal transduction pathway leading to activation of mitogen-activated protein kinase (MAPK) and nuclear factor kappaB (NF-kappaB), and degradation of IkappaB, the NF-kappaB inhibitor. TLR2 co-stimulation by porin resulted in T cell expansion by inducing both proliferation and survival of the CD4(+) T cells. Extracellular signal-regulated kinase (ERK)1/2 activation inhibitor U0126 and NF-kappaB translocation inhibitor SN-50 significantly inhibited proliferation of T cells, highlighting a direct role of ERK and NF-kappaB in the process. However, cell survival involving Bcl-X(L) induction was found to be regulated essentially by ERK with no significant role of NF-kappaB. Porin-induced proliferation was supported by induction of IL-2 and CD25 that are known to play a pivotal role in T cell expansion. Apart from inducing T cell proliferation, porin triggered effector functions of the cells, evident from TLR2- and MyD88-dependent release of type 1 cytokines tumor necrosis factor (TNF) and interferon (IFN)-gamma along with the induction of type 1 chemokines macrophage-inflammatory protein (MIP)-1alpha and MIP-1beta and their receptor CCR5. The proliferation, survival and effector function of CD4(+) T cells through TLR2 co-stimulation show the capability of porin to directly turn adaptive immunity into action.

TLR5 stimulation is sufficient to trigger reactivation of latent HIV-1 provirus in T lymphoid cells and activate virus gene expression in central memory CD4+ T cells

When effector CD4+ T cells carrying integrated HIV-1 proviruses revert back to a resting memory state, the virus can remain silent in those cells for years. Following re-exposure to the nominal antigen or in response to other stimuli (e.g. pro-inflammatory cytokines), these cells can begin to produce virus. Here we demonstrate that TLR5 stimulation induces activation of NF-kappaB and reactivate latent HIV-1 in CD4+ T lymphoid cells. Interestingly, we report also that TLR5 engagement leads to virus gene expression in quiescent central memory CD4+ T cells, a cell population recognized as a major reservoir in infected individuals. This study supports the hypothesis that translocation of microbes that can engage pathogen recognition receptors might play a dominant role in chronic immune activation seen in HIV-1-infected individuals and promote virus replication and dissemination.

Human cholesteryl ester transfer protein expression enhances the mouse survival rate in an experimental systemic inflammation model: a novel role for CETP

Mice expressing human cholesteryl ester transfer protein (huCETP) are more resistant to Escherichia coli bacterial wall LPS because death rates 5 days after intraperitoneal inoculation of LPS were higher in wild-type than in huCETP+/+ mice, whereas all huCETP+/+ mice remained alive. After LPS inoculation, plasma concentrations of TNF-alpha and IL-6 increased less in huCETP+/+ than in wild-type mice. LPS in vitro elicited lower TNF-alpha production by CETP expressing than by wild-type macrophages. In addition, TNF-alpha production by RAW 264.7 murine macrophages increased on incubation with LPS but decreased in a dose-dependent manner when human CETP was added to the medium. Human CETP in vitro enhanced the LPS binding to plasma high-density lipoprotein/low-density lipoprotein. The liver uptake of intravenous infused 14C-LPS from Salmonella typhimurium was greater in huCETP+/+ than in wild-type mice. Present data indicate for the first time that CETP is an endogenous component involved in the first line of defense against an exacerbated production of proinflammatory mediators.

Chronic restraint stress promotes immune suppression through toll-like receptor 4-mediated phosphoinositide 3-kinase signaling

Stress, either psychological or physical, can have a dramatic impact on the immune system. Toll-like receptors (TLRs) play a pivotal role in the induction of innate and adaptive immune response. We have reported that stress modulates the immune response in a TLR4-dependent manner. However, the mechanisms underlying TLR4-mediated signaling in stress modulation of immune system have not been identified. Here, we demonstrate an essential role for the TLR4-mediated phosphoinositide 3-kinase (PI3K)/Akt signaling. PI3K inhibition by inhibitors wortmannin or LY294002 abrogated protection of stress-induced immune suppression in TLR4-deficient mice compared with TLR4-deficient mice that did not receive the inhibitors. The mechanisms by which PI3K are increased in the TLR4-deficient lymphocytes may involve increased phosphorylation of Akt as well as increased phosphorylation of glycogen synthase kinase-3 beta (GSK-3 beta). The stress-mediated suppression of T help 1 (Th1) cytokine and increased production of Th2 cytokine was greatly reduced in TLR4 deficient mice compared with the wild type mice. Moreover, inhibition of PI3K diminished protection of the above Th1 and Th2 changes caused by stress in TLR4-deficient mice compared with non-stressed mice and the wild type mice. Our data demonstrated that TLR4 negatively regulates PI3K activity in wild type mice, leading to the observed the stress-induced immune response. The higher levels of PI3K prevent TLR4 deficient mice from the stress-induced immune response. Therefore, stress modulates the immune system through TLR4-mediated PI3K/Akt signaling.

The TLR3 agonist poly(I:C) targets CD8+ T cells and augments their antigen-specific responses upon their adoptive transfer into naïve recipient mice

We have recently reported that the toll-like receptor 3 (TLR3) agonist poly(I:C) induces adjuvant effects to post vaccination CD8+ T cells responses through rapid induction of innate mediators, including NK cells, macrophages, dendritic cells (DCs), and inflammatory cytokines. However, whether this TLR3 agonist directly targets CD8+ T cells needs to be carefully investigated. In this study, we found that optimal post vaccination CD8+ T cell responses to ex vivo DC-based vaccination requires triggering of TLR3 signaling pathway in DCs in vitro as well as in the recipient host, indicating a role for other cell types. Real-time PCR analysis revealed that TLRs (TLR1-TLR13) are expressed in purified (>99% pure) CD4+ and CD8+ T cells from C57BL/6 and BALB/c mice, where the magnitude of the expression was strain and cell type dependent. In vitro, treatment of these purified T cells with poly(I:C) modulated the expression of TLRs including TLR3. Furthermore, non-specific and antigen-specific stimulation of CD8+ T cells by phorbol myristate acetate and MHC class I peptide-pulsed splenocytes, respectively, modulated TLR expression in purified CD4+ and CD8+ T cells. Importantly, brief conditioning of purified naïve TCR transgenic OT-1 (CD8+) T cells in vitro with poly(I:C) induced activation of these cells in absence of antigen stimulation. Interestingly, when these in vitro poly(I:C)-conditioned OT-1 cells were adoptively transferred into naïve recipient followed by peptide vaccination, they showed superior expansion and activation to their naïve counterparts. These results suggest that CD8+ T cells can be activated by triggering their TLR3. Furthermore, the data support the notion of direct involvement of TLRs in adaptive immune responses.

Live imaging of Toll-like receptor 2 response in cerebral ischaemia reveals a role of olfactory bulb microglia as modulators of inflammation

Activation of microglial cells in response to ischaemic injury, inflammatory and/or immune stimuli is associated with the marked induction of Toll-like receptor 2 (TLR2). At present, little is known about the spatial and temporal sequence of events, micro-regional specificities and the potential long term role of the TLR2 response to brain injuries. To investigate microglial activation/TLR2 response in real time, we generated a transgenic mouse model bearing the dual reporter system luciferase/green fluorescent protein under transcriptional control of a murine TLR2 promoter. In this model, transcriptional activation of TLR2 was visualized in the brains of live animals using biophotonic/bioluminescence molecular imaging and a high resolution/sensitivity charged coupled device camera. It was found that TLR2 induction/microglial activation has a marked chronic component after ischaemic injury and may last several months after the initial attack. The pro-inflammatory response was not restricted to the site of ischaemic injury but was also evident in the olfactory bulb. A significant TLR2 response was first seen in the olfactory bulb 6 h after stroke and several hours before the increase in photon emission over the site of infarction. This sequence of events was further confirmed by immunohistochemistry. A similar early TLR2 response from olfactory bulb microglia was observed in the brain's immune response to pathogens. We therefore propose that, owing to their unique situation, receiving and translating numerous inputs from the brain as well as from the environment, olfactory bulb microglia may serve as sensors and/or modulators of brain inflammation.

Severe tuberculosis induces unbalanced up-regulation of gene networks and overexpression of IL-22, MIP-1alpha, CCL27, IP-10, CCR4, CCR5, CXCR3, PD1, PDL2, IL-3, IFN-beta, TIM1, and TLR2 but low antigen-specific cellular responses

The immune mechanisms by which early host-mycobacterium interaction leads to the development of severe tuberculosis (TB) remain poorly characterized in humans. Here, we demonstrate that severe TB in juvenile rhesus monkeys down-regulated many genes in the blood but up-regulated selected genes constituting gene networks of Th17 and Th1 responses, T cell activation and migration, and inflammation and chemoattractants in the pulmonary and lymphoid compartments. Overexpression (450-2740-fold) of 13 genes encoding inflammatory cytokines and receptors (IL-22, CCL27, MIP-1alpha, IP-10, CCR4, CCR5, and CXCR3), immune dysfunctional receptors and ligands (PD1 and PDL2), and immune activation elements (IL-3, IFN-beta, TIM1, and TLR2) was seen in tissues, with low antigen-specific cellular responses. Thus, severe TB in macaques features unbalanced up-regulation of immune-gene networks without proportional increases in antigen-specific cellular responses.

Phenotypic differences between cord blood and adult peripheral blood

BACKGROUND AND OBJECTIVES

Neonates are more susceptible to infections than adults, due to a less mature immune system. The objective of this study was to compare the immunophenotypes of cord blood (CB) and adult peripheral blood (APB) and to establish whether or not there are immunophenotypical differences.

METHODS

CB and APB were collected into CPD anticoagulant. Whole blood was stained with fluorochrome conjugated antibodies, cells were fixed, red cells were lysed, and samples were run in a FACSCanto flow cytometer.

RESULTS

Plots of SSC vs. CD45 showed two lymphocyte-like populations in CB with the same low SSC characteristics while there was only one low SSC lymphoid population in APB. The CD45dim population included the majority of CD34+ cells, but it also included T, B, NKT, and NK cells. The percentages of CD3+, CD3+CD4+, CD3+CD8+, CD19+, CD3+CD56+, and CD3-CD56+ in the CD45high gate of CB were similar to the percentages obtained for APB. Meanwhile, in the CD45dim gate, the percentages were either lower (CD3+, CD3+CD4+, CD3+CD8+) or higher (CD19+, CD3+CD56+, CD3-CD56+) than in the CD45high gate.

CONCLUSIONS

CB presents two lymphoid populations defined by different levels of expression of the phosphatase CD45; the CD45dim subsets likely represent cells with elevated proliferative activity possibly due to the differential expression of CD45 but still not yet immunologically mature with regard to immunophenotype and function.

VIP balances innate and adaptive immune responses induced by specific stimulation of TLR2 and TLR4

Crohn's disease (CD) is a chronic intestinal inflammatory pathology, which develops as a result of innate immune signals, such as the activation of Toll-like receptors (TLRs), and adaptive immune signals, including Th1 cytokine release. We have recently demonstrated in TNBS-induced colitis, a murine model of CD, that VIP plays a homeostatic role, by reducing TNBS-induced TLR2 and TLR4 expression to control levels. The purpose of this paper is to elucidate for the first time, the physiological relevance of VIP specific control of innate and adaptive immune responses through TLR2 and TLR4 ligands. In addition, we investigated the effect of VIP on regulatory activity of T regulatory (Treg) cells in the TNBS-colitis model. First, we found that VIP downregulated the inflammatory response elicited in mesenteric lymph node cell cultures by treatment with the TLR2 ligand Pam3Cys, or the TLR4 ligand lipopolysaccharide (LPS), reducing the production of the chemokine CXCL1. Also, treatment with VIP impaired the induction of Th1 responses by decreasing p70 interleukin (IL)-12 and interferon gamma (IFN-gamma) levels after TLR2/TLR4 stimulation in culture. Besides, VIP treatment restored in vivo the numbers of TLR2 and TLR4 positive CD4+CD25+ T lymphocytes, augmented by TNBS administration, and increased the expression of molecules involved in regulatory T cell function, such as Foxp3 and TGF-beta. In conclusion, the ability of VIP to down-regulate uncontrolled inflammation by targeting TLR-mediated responses and regulatory T cell activity could be used as a new alternative therapy for intestinal inflammatory/autoimmune disorders.

Human Th1 differentiation induced by lipoarabinomannan/lipomannan from Mycobacterium bovis BCG Tokyo-172

Mycobacterium tuberculosis (tubercle bacilli) and the related acid-fast bacteria including Mycobacterium bovis Bacille Calmett-Guerin (BCG) have a characteristic cell wall (CW) containing various lipoglycans and glycolipids. Such lipoglycans have been reported to activate type-I inflammatory responses via dendritic cells (DCs) through Toll-like receptor 2. In this study, lipoglycans, lipoarabinomannan (LAM), lipomannan (LM) and phosphatidylinositol mannoside (PIM), were purified from the CW fractions of M. bovis BCG Tokyo-172, and the effect on the differentiation of human peripheral blood naive CD4 T cells into T(h)1 and T(h)2 was examined. LAM/LM molecules enhanced T(h)1 differentiation under both T(h)1 and T(h)2 conditions, whereas some other glycolipids and phospholipid enhanced T(h)2 differentiation under T(h)2 conditions. Other components had little effect under the given conditions. Even in highly purified CD4 T cell cultures, LAM/LM enhanced T(h)1 generation only under T(h)1 culture conditions. These results indicate that LAM/LM possesses a potent augmenting activity in T(h)1 differentiation in human CD4 T cells. LAM/LM appeared to act directly on naive CD4 T cells to enhance T(h)1 differentiation under T(h)1 culture conditions, while acting indirectly to up-regulate the generation of T(h)1 cells via IL-12/DCs under T(h)1 and T(h)2 conditions. Therefore, these results provide the first evidence indicating that LAM/LM from M. bovis BCG may possess a potent modulating activity in the human system, and thus supporting the strategy for the use of BCG components in the vaccine development for such T(h)2 diseases as allergic asthma and rhinitis.

Therapeutic impact of toll-like receptors on inflammatory bowel diseases: a multiple-edged sword

Recent studies have begun to define the mechanisms through which Toll-like receptors (TLRs) regulate intestinal homeostasis in health and disease. Current therapies for inflammatory bowel diseases (IBDs) mostly aim at interrupting the inflammatory cascade through agents that regulate TH1 or TH2 cytokine responses. As recognition grows for TLR dysfunction to play a role in IBD pathogenesis, TLRs could provide another valid interventional target for novel therapy development. However, seemingly contradictory results from studying different murine models of colitis have so far confounded whether therapeutically useful modulation of TLRs is best accomplished by activating, inhibiting, or rather a combination of both at different stages of mucosal disease. This review evaluates potential strategies as well as their rationale and future prospects.