Helper Cell Function Research Articles

MicroRNA-mediated regulation of T helper cell differentiation and plasticity

CD4(+) T helper (TH) cells regulate appropriate cellular and humoral immune responses to a wide range of pathogens and are central to the success of vaccines. However, their dysregulation can cause allergies and autoimmune diseases. The CD4(+) T cell population is characterized not only by a range of distinct cell subsets, such as TH1, TH2 and TH17 cells, regulatory T cells and T follicular helper cells--each with specific functions and gene expression programmes--but also by plasticity between the different TH cell subsets. In this Review, we discuss recent advances and emerging ideas about how microRNAs--small endogenously expressed oligonucleotides that modulate gene expression--are involved in the regulatory networks that determine TH cell fate decisions and that regulate their effector functions.

Oesophagostomum dentatum Extract Modulates T Cell-Dependent Immune Responses to Bystander Antigens and Prevents the Development of Allergy in Mice

One third of the human population is currently infected by one or more species of parasitic helminths. Certain helminths establish long-term chronic infections resulting in a modulation of the host’s immune system with attenuated responsiveness to “bystander” antigens such as allergens or vaccines. In this study we investigated whether parasite-derived products suppress the development of allergic inflammation in a mouse model. We show that extract derived from adult male Oesophagostomum dentatum (eMOD) induced Th2 and regulatory responses in BALB/c mice. Stimulation of bone marrow-derived dendritic cells induced production of regulatory cytokines IL-10 and TGF-beta. In a mouse model of birch pollen allergy, co-administration of eMOD with sensitizing allergen Bet v 1 markedly reduced the production of allergen-specific antibodies in serum as well as IgE-dependent basophil degranulation. Furthermore, eMOD prevented the development of airway inflammation, as demonstrated by attenuation of bronchoalveolar lavages eosinophil influx, peribronchial inflammatory infiltrate, and mucus secretion in lungs and IL-4 and IL-5 levels in lung cell cultures. Reduced secretion of Th2-related cytokines by birch pollen-re-stimulated splenocytes and mesenteric lymph node cells was observed in eMOD-treated/sensitized and challenged mice in comparison to sensitized and challenged controls. The suppressive effects of eMOD were heat-stable. Immunization with model antigens in the presence of eMOD reduced production of antibodies to thymus-dependent but not to thymus-independent antigen, suggesting that suppression of the immune responses by eMOD was mediated by interference with antigen presenting cell or T helper cell function but did not directly suppress B cell function. In conclusion, we have shown that eMOD possesses immunomodulatory properties and that heat-stable factors in eMOD are responsible for the dramatic suppression of allergic responses in a mouse model of type I allergy. The identification and characterization of parasite-derived immune-modulating molecules might have potential for designing novel prophylactic/therapeutic strategies for immune-mediated diseases.

AB0323 Vitamin D receptor gene polymorphisms in rheumatoid arthritis

BackgroundThe etiology of rheumatoid arthritis (R.A.), an autoimmune, polygenic, inflammatory disease, has not yet been clarified despite the intense research1. In addition to its more commonly known metabolic effects such...

Novel IL-9-Secreting innate helper cells promote oral antigen-induced anaphylaxis (P6249)

Abstract IgE-mediated food allergy is manifested by an overactive T-helper 2 immune response to dietary antigens in the gastrointestinal (GI) tract. Interleukin (IL)-9 promote intestinal mastocytosis which allow the development of oral antigen-induced anaphylaxis. However, little is known about the primary cellular sources of IL-9 or the mechanisms that promote intestinal mastocytosis. Here, we report the identification of multifunctional IL-9-producing innate helper cells (IHC9) that secrete prodigious amounts of TH2 cytokines and mast cell protease-1 (MCPt-1) in response to IL-33 and antigen/IgE complex crosslinking, respectively. Repeated intragastric antigen challenge induces significant accumulations of both intestinal IHC9 and CD4+TH2 cells, which correlate positively with symptoms and susceptibility to oral antigen-induced anaphylaxis. IHC9 development requires T cells and IL-4R, not IL-9R, signaling. The failure of irradiated mice reconstituted with STAT6-deficient bone marrow to generate IHC9 was accompanied by reduced serum MCPt-1, intestinal TH2 inflammation, mastocytosis, and goblet cell hyperplasia and loss of allergic diarrhea. Furthermore, inhibition of food allergy symptoms in mice ablated of IHC9 by anti-FcϵRIα antibody treatment could be reversed by adoptive transfer of IHC9. Thus, IHC9 represent a new type of innate helper cell lineage and function in promoting intestinal TH2 inflammation and mastocytosis that drive IgE-mediated anaphylaxis.

Ex Vivo Enzymatic Treatment of Aged CD4 T Cells Restores Cognate T Cell Helper Function and Enhances Antibody Production in Mice

Previous in vitro studies showed that CD4 T cells from old mice have defects in TCR signaling, immune synapse formation, activation, and proliferation. We reported that removing a specific set of surface glycoproteins by ex vivo treatment with O-sialoglycoprotein endopeptidase (OSGE) can reverse many aspects of the age-related decline in CD4 T cell function. However, the specific mechanism by which this process occurs remains unclear, and it is unknown whether this enzymatic treatment can also restore important aspects of adaptive immunity in vivo. By using an in vivo model of the immune response based on adoptive transfer of CD4 T cells from pigeon cytochrome C-specific transgenic H-2(k/k) TCR-Vα(11)Vβ(3) CD4(+) mice to syngeneic hosts, we demonstrate that aging diminishes CD28 costimulatory signals in CD4 T cells. These age-associated defects include changes in phosphorylation of AKT and expression of glucose transporter type I, inducible T cell costimulatory molecule, and CD40L, suggesting that the lack of CD28 costimulation contributes to age-dependent loss of CD4 function. All of these deficits can be reversed by ex vivo OSGE treatment. Blocking B7-CD28 interactions on T cells prevents OSGE-mediated restoration of T cell function, suggesting that changes in surface glycosylation, including CD28, may be responsible for the age-related costimulation decline. Finally, we show that the age-related decline in CD4 cognate helper function for IgG production and long-term humoral immunity can also be restored by OSGE treatment of CD4 T cells prior to adoptive transfer.

Lentivirally overexpressed T-bet regulates T-helper cell lineage commitment in chronic hepatitis B patients

Chronic hepatitis B virus (HBV) infection is commonly considered to occur as a result of disturbance of the immune system. T-box expressed in T cells (T-bet) is an essential transcription factor for T helper (Th) cell differentiation and function. The aim of this study was to investigate the effect of T-bet overexpression on Th cell differentiation and the possible mechanism in chronic hepatitis B (CHB) patients. CD4+ T cells from the peripheral blood of 23 CHB patients, 8 acute hepatitis B (AHB) patients and 10 healthy controls were isolated. T-bet mRNA expression of CD4+ T cells was detected by quantitative real-time polymerase chain reaction (PCR). The T-bet DNA fragment was subcloned into the pGC-FU vector containing GFP to generate a recombinant lentiviral vector, pGC-FU-T-bet, while a no-load pGC-FU vector was used as the negative control. After transduction into CD4+ T cells from another 22 CHB patients, the induction of Th1- and Th2-type cytokines was assayed by an enzyme-linked immunosorbent assay (ELISA), and RT-PCR and western blot analysis were used to measure the mRNA and transcription levels of H2.0-like homeobox (HLX1), GATA-3 and STAT-6. T-bet mRNA expression in CD4+ T cells from AHB patients was enhanced compared with CHB patients and healthy controls. Th1-type cytokines and HLX1 expression was upregulated, while Th2-type cytokines and GATA-3 and STAT-6 expression was repressed after lentiviral introduction of T-bet. In conclusion, lentivirally overexpressed T-bet regulates Th cell lineage commitment in CHB patients, which may be mediated by regulating HLX1, GATA-3 and STAT-6 expression.

Memory CD4 T cells protect against influenza A virus through both an interferon gamma-dependent and multiple interferon gamma-independent mechanisms (105.31)

Abstract Memory CD4 T cells provide strong protection against influenza A virus (IAV), but the mechanisms and cellular interactions critical for their antiviral impact are not well described. A more complete understanding of how memory CD4 T cells contribute to viral clearance could improve T cell-based vaccine strategies aimed at protecting against both seasonal and pandemic IAV strains. Here, we show that IAV-specific Th1- and Th17-polarized memory CD4 T cells, as well as memory cells primed by IAV, protect otherwise naïve mice against lethal IAV challenge. We systematically deconstruct this protective response utilizing mice deficient for B cells, T cells, or both, to reveal multiple, distinct mechanisms of protection. First, in the absence of other T cells, memory CD4 T cells synergize with B cells to provide protection that is dependent on neutralizing antibodies but independent of characterized CD4 T cell helper functions. Second, in the absence of B cells, memory CD4 T cells synergize with CD8 T cells to promote equivalent viral clearance. These mechanisms of protection are both fully independent of interferon gamma (IFNγ) production by memory CD4 T cells. Third, in the absence of both B and CD8 T cells, memory CD4 T cells directly control IAV. Strikingly, this direct control is critically dependent on IFNγ. These results support a central role for memory CD4 T cells in orchestrating and directly participating in distinct forms of heterosubtypic immunity against IAV.

STAT5 Protein Negatively Regulates T Follicular Helper (Tfh) Cell Generation and Function

Recent work has identified a new subset of CD4(+) T cells named as Tfh cells that are localized in germinal centers and critical in germinal center formation. Tfh cell differentiation is regulated by IL-6 and IL-21, possibly via STAT3 factor, and B cell lymphoma 6 (Bcl6) is specifically expressed in Tfh cells and required for their lineage specification. In the current study, we characterized the role of STAT5 in Tfh cell development. We found that a constitutively active form of STAT5 effectively inhibited Tfh differentiation by suppressing the expression of Tfh-associated factors (CXC motif) receptor 5 (CXCR5), musculoaponeurotic fibrosarcoma (c-Maf), Bcl6, basic leucine zipper transcription factor ATF-like (Batf), and IL-21, and STAT5 deficiency greatly enhanced Tfh gene expression. Importantly, STAT5 regulated the expression of Tfh cell suppressor factor B lymphocyte-induced maturation protein 1 (Blimp-1); STAT5 deficiency impaired Blimp-1 expression and resulted in elevated expression of Tfh-specific genes. Similarly, inhibition of IL-2 potentiated Tfh generation, associated with dampened Blimp-1 expression; Blimp-1 overexpression inhibited Tfh gene expression in Stat5-deficient T cells, suggesting that the IL-2/STAT5 axis functions to regulate Blimp-1 expression. In vivo, deletion of STAT5 in CD4(+) T cells resulted in enhanced development of Tfh cells and germinal center B cells and led to an impairment of B cell tolerance in a well defined mouse tolerance model. Taken together, this study demonstrates that STAT5 controls Tfh differentiation.

Aging of the CD4 T Cell Compartment.

Higher morbidity and mortality following infections, particularly influenza, is observed in the elderly population. Because of this, people over 65 years old are often targeted for preventive immunization. Many vaccines, however, are not as effective in generating protective antibodies in older individuals. CD4+ T cells, through their B cell helper functions, play a central role in the humoral response. Aging has deleterious effects on the immune system, and understanding how aging impairs CD4+ T cell functions is of critical importance to design new immunization and treatment strategies targeted to the elderly population. In this paper, we review some of the qualitative and quantitative changes in the CD4+ T cell compartment that arise with aging. We also summarize the age-related intrinsic defects that impact naïve, memory and regulatory CD4+ T cell functions.

T helper1/t helper2 cells and resistance/susceptibility to leishmania infection: is this paradigm still relevant?

Work in large part on Leishmania major in the 1980s identified two distinct apparently counter-regulatory CD4+ T cell populations, T helper (h)1 and Th2, that controlled resistance/susceptibility to infection respectively. However, the generation of IL-4−/− mice in the 1990s questioned the paramount role of this Th2 archetypal cytokine in the non-healing response to Leishmania infection. The more recent characterization of CD4+ T cell regulatory populations and further effector CD4+ T helper populations, Th17, Th9, and T follicular (f)h cells as well as the acknowledged plasticity in T helper cell function has further added to the complexity of host pathogen interactions. These interactions are complicated by the multiplicity of cells that respond to CD4+ T cell subset signatory cytokines, as well as the diversity of Leishmania species that are often subject to significantly different immune-regulatory controls. In this article we review current knowledge with regard to the role of CD4+ T cells and their products during Leishmania infection. In particular we update on our studies using conditional IL-4Rα gene-deficient mice that have allowed dissection of the cell interplay dictating the disease outcomes of the major Leishmania species infecting humans.

CD4 T Cells Promote CD8 T Cell Immunity at the Priming and Effector Site during Viral Encephalitis

CD4 T cell activation during peripheral infections not only is essential in inducing protective CD8 T cell memory but also promotes CD8 T cell function and survival. However, the contributions of CD4 T cell help to antiviral CD8 T cell immunity during central nervous system (CNS) infection are not well established. Encephalitis induced by the sublethal coronavirus JHMV was used to identify when CD4 T cells regulate CD8 T cell responses following CNS infection. Peripheral expansion of virus-specific CD8 T cells was impaired when CD4 T cells were ablated prior to infection but not at 4 days postinfection. Delayed CD4 T cell depletion abrogated CD4 T cell recruitment to the CNS but only slightly diminished CD8 T cell recruitment. Nevertheless, the absence of CNS CD4 T cells was associated with reduced gamma interferon (IFN-γ) and granzyme B expression by infiltrating CD8 T cells, increased CD8 T cell apoptosis, and impaired control of infectious virus. CD4 T cell depletion subsequent to CD4 T cell CNS migration restored CD8 T cell activity and virus control. Analysis of γc-dependent cytokine expression indicated interleukin-21 (IL-21) as a primary candidate optimizing CD8 T cell activity within the CNS. These results demonstrate that CD4 T cells play critical roles in both enhancing peripheral activation of CD8 T cells and prolonging their antiviral function within the CNS. The data highlight the necessity for temporally and spatially distinct CD4 T cell helper functions in sustaining CD8 T cell activity during CNS infection.

B cell–helper neutrophils stimulate the diversification and production of immunoglobulin in the marginal zone of the spleen

Neutrophils utilize immunoglobulins (Igs) to clear antigen, but their role in Ig production is unknown. Here we identified neutrophils around the marginal zone (MZ) of the spleen, a B cell area specialized in T-independent Ig responses to circulating antigen. Neutrophils colonized peri-MZ areas after post-natal mucosal colonization by microbes and enhanced their B-helper function upon receiving reprogramming signals from splenic sinusoidal endothelial cells, including interleukin 10 (IL-10). Splenic neutrophils induced Ig class switching, somatic hypermutation and antibody production by activating MZ B cells through a mechanism involving the cytokines BAFF, APRIL and IL-21. Neutropenic patients had fewer and hypomutated MZ B cells and less preimmune Igs to T-independent antigens, which indicates that neutrophils generate an innate layer of antimicrobial Ig defense by interacting with MZ B cells.

In Vitro Generation of Influenza-Virus Specific T Cells for Adoptive Immunotherapy,

Abstract 4040Influenza viruses cause fatal respiratory infections in stem cell transplant patients. Specific T cells provide long-lived adaptive immunity to influenza and the potential for generating such cells for clinical use was investigated. The inactivated influenza vaccine (Fluvax, CSL Australia) was used as the antigen source. Only reagents and culture media approved for clinical manufacture were used. Monocyte-derived dendritic cells (MoDC) pulsed with Fluvax were used to stimulate autologous PBMC at a responder to stimulator ratio of 10:1. On Day 7, a second stimulation was performed. 20U/ml IL-2 was added from Day 7 and 50U/ml IL-2 from Day 14 onwards. Media exchanges were performed as required using fresh medium containing IL-2.Over 21 days of culture, a mean fold increase of 26.3 in cell number was observed (n=7). Cultures were mainly T cells (mean 92.9%) with effector and central memory phenotypes. CD4 cells dominated (mean 78.1%) with a lower percentage of CD8 cells (mean 14.9%). Following expansion, CD154 was expressed on 8.1% of CD4 cells (<1% in unstimulated cells). Both CD4 (mean 26.3%) and CD8 (mean 3.2%) cells produced one or more of the Th1 cytokines IFNg, TNFa and/or IL-2 when restimulated with Fluvax antigen pulsed MoDC. Most responding CD4 cells produced all three cytokines simultaneously, while CD8 cells primarily produced IFNg alone. A mean of 11.1% CD4 and 9.1% of CD8 cells mobilized CD107 on the cell surface when restimulated with Fluvax. Th1 cytokines were produced in response to stimulation with antigens derived from individual H1N1, H3N2 and Brisbane virus strains by the CD4 subset in all of 6 cases and CD8 subset in 2 of 6 cases. In addition, both CD4 and CD8 cells proliferated on restimulation with Fluvax or antigen from H1N1, H3N2 or Brisbane strains.In conclusion, we demonstrate a clinically applicable method that yields high numbers of highly reactive T cells specific for influenza viruses including the H1N1 strain. Cells express a phenotype of activated antigen specific cells capable of B cell helper function. We propose that reconstructing host immunity through adoptive transfer of donor derived influenza virus specific T cells possibly combined with early post-transplant influenza vaccination will reduce the frequency of influenza-related deaths in the period of severe immune suppression that follows allogeneic stem cell transplant. Disclosures:Off Label Use: Use of influenza vaccine for in vitro cell generation.

Absence of Cross-Presenting Cells in the Salivary Gland and Viral Immune Evasion Confine Cytomegalovirus Immune Control to Effector CD4 T Cells

Horizontal transmission of cytomegaloviruses (CMV) occurs via prolonged excretion from mucosal surfaces. We used murine CMV (MCMV) infection to investigate the mechanisms of immune control in secretory organs. CD4 T cells were crucial to cease MCMV replication in the salivary gland (SG) via direct secretion of IFNγ that initiated antiviral signaling on non-hematopoietic cells. In contrast, CD4 T cell helper functions for CD8 T cells or B cells were dispensable. Despite SG-resident MCMV-specific CD8 T cells being able to produce IFNγ, the absence of MHC class I molecules on infected acinar glandular epithelial cells due to viral immune evasion, and the paucity of cross-presenting antigen presenting cells (APCs) prevented their local activation. Thus, local activation of MCMV-specific T cells is confined to the CD4 subset due to exclusive presentation of MCMV-derived antigens by MHC class II molecules on bystander APCs, resulting in IFNγ secretion interfering with viral replication in cells of non-hematopoietic origin.

Impact of aging on CD4 T cell helper functions (104.6)

Abstract Impairment of the immune system in older people leads to increased susceptibility to infection and reduced antibody production following immunization. We have previously shown that intrinsic defects in CD4 T cell function occur in aged mice and that this negatively impacts the antibody response. In addition, other age-related changes can impact CD4 T cell priming. Using an adoptive transfer model, we show that the trafficking of young TCR Tg CD4 T cells to the T cell zones of secondary lymphoid organs is impaired when they are transferred into aged hosts compared to young hosts. This correlates with delayed expansion and reduced activation as measured by CFSE dilution and CD69 expression, respectively. Using immunofluorescent staining of spleen sections, we demonstrate that the structure of the B cell follicles and the expression of CCL21 are disorganized in aged hosts compared to young hosts, likely causing this reduced trafficking in aged hosts. This also likely contributes to the reduced induction of Tfh cells in the lymph nodes of aged mice. Finally, we found that fewer aged cells produce cytokines and that the pattern of cytokine production is also different, aged mice having more cells producing IL-17 but less cells producing IL-4, IL-10 and IFNγ than young mice. Thus, not only is the CD4 T cell response reduced with age, it is also qualitatively different which could account for reduced induction of protection following immunization.

Helper Activity of Natural Killer Cells During the Dendritic Cell-mediated Induction of Melanoma-specific Cytotoxic T Cells

Natural killer (NK) cells have been shown to mediate important immunoregulatory "helper" functions in addition to their cytolytic activity. In particular, NK cells are capable of preventing maturation-related dendritic cell (DC) "exhaustion," inducing the development of "type-1 polarized" mature DCs (DC1) with an enhanced ability to produce interleukin (IL)-12p70, a factor essential for type-1 immunity and effective anticancer responses. Here we show that the NK cell-mediated type-1 polarization of DCs can be applied in the context of patients with advanced cancer to enhance the efficacy of DCs in inducing tumor-specific cytotoxic T lymphocytes. NK cells isolated from patients with late-stage (stage III and IV) melanoma responded with high interferon-γ production and the induction of type-1-polarized DCs on exposure to defined combinations of stimulatory agents, including interferon-α and IL-18. The resulting DCs showed strongly-enhanced IL-12p70 production on subsequent T-cell interaction compared with immature DCs (average of 19-fold enhancement) and nonpolarized IL-1β/TNF-α/IL-6/PGE(2)-matured "standard" DCs (average of 215-fold enhancement). Additional inclusion of polyinosinic: polycytidylic acid during NK-DC cocultures optimized the expression of CD80, CD86, CD40, and HLA-DR on the resulting (NK)DC1, increased their CCR7-mediated migratory responsiveness to the lymph node-associated chemokine CCL21, and further enhanced their IL-12-producing capacity. When compared in vitro with immature DCs and nonpolarized standard DCs, (NK)DC1 were superior in inducing functional melanoma-specific cytotoxic T lymphocytes capable of recognizing multiple melanoma-associated antigens and killing melanoma cells. These results indicate that the helper function of NK cells can be used in clinical settings to improve the effectiveness of DC-based cancer vaccines.

HBsAg-specific regulatory T cells are present in patients with chronic HBV infection

We analysed the frequency and phenotypic characteristics of HBsAg-specific regulatory T cells (HBsAg-Treg) in individuals with different HBV infection status and investigated their effect on cellular immune responses as well as the mechanisms underlying their regulatory function. In addition we assessed, whether HBsAg-Treg have an inhibitory effect on anti-HBs production by suppressing corresponding T helper cell functions. A total of 45 subjects including patients with chronic (n=16) and resolved (n=10) hepatitis B, solely anti-HBc-positive (n=9) and vaccinated (n=10) individuals were tested. Immune responses were determined by Elispot analysis of HBsAg-specific T cells and anti-HBs-producing B cells. HBsAg-Treg were detectable in 9/16 chronic carriers and 4/9 solely anti-HBc-positive individuals, but neither in patients with resolved HBV infection nor in vaccinated individuals. Circulating HBsAg-Treg show a CD4+/CD25+ phenotype, produce exclusively IL-10 and suppress function of HBsAg-specific CD4+ effector T cells in vitro. Suppression of effector cells determined in depletion and IL-10 neutralization experiments is dose-dependent, requires direct cell-cell contact, and is independent of IL-10. T cell epitope mapping revealed the same epitope specificity for HBsAg-Treg and CD4+ effector T cells, respectively. Depletion of CD25+/CD4+ Treg enhances HBsAg-specific effector T cell responses, however it has no impact on the number of detectable anti-HBs-secreting B cells in all tested groups. Our data suggest that HBsAg-specific Treg are exclusively induced in patients with chronic HBV infection. They may be responsible for or at least contribute to the inadequate cellular immune response against HBsAg by dampening effector T cell responses. The inability of chronic carriers to develop anti-HBs, however, does not seem to be determined by the presence of HBsAg-Treg only.

Mast Cell-Derived IL-10 Suppresses Germinal Center Formation by Affecting T Follicular Helper Cell Function

The most prevalent cancer diagnosed in the world is sunlight-induced skin cancer. In addition to being a complete carcinogen, UV radiation, the causative agent of skin cancer, induces immune suppression. Because UV-induced immune suppression is a well-recognized risk factor for skin cancer induction, it is crucial to understand the mechanisms underlying UV-induced immune suppression. Mast cells, which have recently emerged as immune regulatory cells, are particularly important in UV-induced immune suppression. UV exposure does not induce immune suppression in mast cell-deficient mice. We report that UV irradiation blocks germinal center (GC) formation, Ab secretion, and T follicular helper (Tfh) cell function, in part by altering the expression of transcription factors BCL-6 and BLIMP-1. No suppression of GC formation, Tfh cell IL-21 expression, or Ab secretion was observed in UV-irradiated mast cell-deficient (Kit(W-sh/W-sh)) mice. When mast cell-deficient mice were reconstituted with wild type mast cells, immune suppression was restored. Reconstituting the mast cell-deficient mice with bone marrow-derived mast cells from IL-10-deficient mice failed to restore the ability of UV radiation to suppress GC formation. Our findings demonstrate a function for mast cells, suppression of Tfh cell production, GC formation, and Ab production in vivo.

Galectin-9 regulates T helper cell function independently of Tim-3

β-Galactoside-binding lectin 9 (galectin-9) is a tandem repeat-type member of the galectin family. It was initially characterized as an eosinophil chemoattractant and an inducer of apoptosis in thymocytes. Subsequently, galectin-9 was identified as a ligand for transmembrane immunoglobulin mucin domain 3 (Tim-3), a type I glycoprotein induced on T cells during chronic inflammation. Work in autoimmune diseases and chronic viral infections have led to the current hypothesis that the function of Tim-3 is to limit immune responses. However, it is still not known to what degree these effects are due to the galectin-9/Tim-3 interaction. In this study, we show that galectin-9 is not limited to the role of a pro-apoptotic agent, but that it can also induce the production of pro-inflammatory cytokines from T helper cells. This effect is dose-dependent and does not require Tim-3. These findings suggest that the effects of galectin-9 on T cells are more complex than previously thought and are mediated by additional receptors apart from Tim-3.

Expressed sequence identification and characterization of the cDNA for Interleukin-4 from the mitogen-stimulated lymphoid tissue of a marsupial, Macropus eugenii

Very few cytokines that are important to the understanding of T helper cell function are characterized in marsupials. Expression of a 645bp cDNA product that codes for a predicted Interleukin-4 peptide of 157 amino acids was detected in the lymph node tissues of Macropus eugenii, the tammar wallaby. Using Rapid Amplification of cDNA Ends, both 5′- and 3′-untranslated regions were identified and a polyadenylation signal and three mRNA instability motifs associated with secreted cytokine molecules were also present. The translated cDNA sequence has a putative signal peptide of 24 amino acids, a predicted secondary structure that is consistent with the short-chain alpha-helical cytokine family and 82% conservation of residues associated with the Interleukin-4 family sequence motif. Comparisons of wallaby nucleotide and predicted peptide sequences with the coding domains of other vertebrate species demonstrate the diversity within this gene family; with nucleotide and amino acid identities of 74% and 59% with opossum, 52% and 32% with human and 38% and 19% with chicken homologues respectively. Despite these differences in sequence conservation, the putative Macropus eugenii Interleukin-4 mature peptide contains conserved structural motifs and predicted receptor-binding residues that suggest that it may retain functional properties associated with this important Th2 cytokine in other mammals.