CD8 T cells inhibit IgE via dendritic cell IL-12 induction that promotes Th1 T cell counter-regulation

Antibody-Suppressor CXCR5+CD8+ T Cells Are More Potent Regulators of Humoral Alloimmunity after Kidney Transplant in Mice Compared to CD4+ Regulatory T Cells

Adoptive cell therapy (ACT), especially with CD4+ regulatory T cells (CD4+ Tregs), is an emerging therapeutic strategy to minimize immunosuppression and promote long-term allograft acceptance, although much research remains to realize its potential. In this study, we investigated the potency of novel Ab-suppressor CXCR5+CD8+ T cells (CD8+ TAb-supp) in comparison with conventional CD25highFoxp3+CD4+ Tregs for suppression of humoral alloimmunity in a murine kidney transplant (KTx) model of Ab-mediated rejection (AMR). We examined quantity of peripheral blood, splenic and graft-infiltrating CD8+ TAb-supp, and CD4+ Tregs in KTx recipients and found that high alloantibody-producing CCR5 knockout KTx recipients have significantly fewer post-transplant peripheral blood and splenic CD8+ TAb-supp, as well as fewer splenic and graft-infiltrating CD4+ Tregs compared with wild-type KTx recipients. ACT with alloprimed CXCR5+CD8+ T cells reduced alloantibody titer, splenic alloprimed germinal center (GC) B cell quantity, and improved AMR histology in CCR5 knockout KTx recipients. ACT with alloprimed CD4+ Treg cells improved AMR histology without significantly inhibiting alloantibody production or the quantity of splenic alloprimed GC B cells. Studies with TCR transgenic mice confirmed Ag specificity of CD8+ TAb-supp-mediated effector function. In wild-type recipients, CD8 depletion significantly increased alloantibody titer, GC B cells, and severity of AMR pathology compared with isotype-treated controls. Anti-CD25 mAb treatment also resulted in increased but less pronounced effect on alloantibody titer, quantity of GC B cells, and AMR pathology than CD8 depletion. To our knowledge, this is the first report that CD8+ TAb-supp cells are more potent regulators of humoral alloimmunity than CD4+ Treg cells.

T-cell responses in asthma exacerbations

OBJECTIVE

Asthma is a chronic lung disease comprising multiple endotypes and characterized by periodic exacerbations. A diverse array of T cells has been found to contribute to all endotypes of asthma in pathogenic and regulatory roles. Here, we review the contributions of CD4+, CD8+, and unconventional T cells in allergic and nonallergic asthma.

DATA SOURCES

Review of published literature pertaining to conventional and unconventional T-cell types in asthma.

STUDY SELECTIONS

Recent peer-reviewed articles pertaining to T cells in asthma, with additional peer-reviewed studies for context.

RESULTS

Much research in asthma has focused on the roles of CD4+ TH cells. Roles for TH2 cells in promoting allergic asthma pathogenesis have been well-described, and the recent description of pathogenic TH2A cells provides additional insight into these responses. Other TH types, notably TH1 and TH17, have been linked to neutrophilic and steroid-resistant asthma phenotypes. Beyond CD4+ T cells, CD8+ Tc2 cells are also strongly associated with allergic asthma. An emerging area for study is unconventional T-cell types, including γδT, invariant natural killer T, and mucosal-associated invariant T cells. Although data in asthma remain limited for these cells, their ability to bridge innate and adaptive responses likely makes them key players in asthma. A number of asthma therapies target T-cell responses, and, although data are limited, they seem to modulate T-cell populations.

CONCLUSION

Given the diversity and heterogeneity of asthma and T-cell responses, there remain many rich avenues for research to better understand the pathogenesis of asthma. Despite the breadth of T cells in asthma, approved therapeutics remain limited to TH2 networks.

Time-dependent dual beneficial modulation of interferon-γ, interleukin 5, and Treg cytokines in asthma patient peripheral blood mononuclear cells by ganoderic acid B

Th2 cytokines play a dominant role in the pathogenesis of allergic asthma. Interferon gamma (IFN-γ), a Th1 cytokine, links to therapeutic mechanisms of allergic asthma. Interleukin (IL)-10, a regulatory cytokine, is involved in the induction of immune tolerance. We previously demonstrated that Anti-Asthma Simplified Herbal Medicine Intervention (ASHMI) suppressed Th2 and increased IFN-γ in patients with asthma and in animal models, but its bioactive compound is unknown. Ganoderic acid beta (GAB) was isolated from Ganoderma lucidum (one herb in ASHMI). Human peripheral blood mononuclear cells (PBMCs) from adult patients with asthma were cultured with GAB or dexamethasone (Dex) in the presence of environmental allergens. The cytokine levels of IL-10, IFN-γ, IL-5, transcription factors T-bet, Foxp-3, and GATA3 were measured. Following 3-day culture, GAB, but not Dex, significantly increased IL-10 and IFN-γ levels by allergic patients' PBMCs. Following 6-day treatment, GAB inhibited IL-5 production, but IL-10 and IFN-γ remained high. Dex suppressed production of all three cytokines. GAB suppressed GATA3 and maintained Foxp-3 and T-bet gene expression, while Dex significantly suppressed GATA3 and T-bet expression. GAB simultaneously increased IL-10, IFN-γ associated with induction of T-bet and Foxp3, while suppressing IL-5, which was associated with suppression of GATA3, demonstrating unique beneficial cytokine modulatory effect, which distinguishes from Dex's overall suppression.

Selective Expansion of Double-Negative iNKT Cells Inhibits the Development of Atopic Dermatitis in Vα14 TCR Transgenic NC/Nga Mice by Increasing Memory-Type CD8+ T and Regulatory CD4+ T Cells

Spontaneous development of atopic dermatitis (AD) in NC/Nga (NC) mice has been attributed to a deficiency in invariant NK T (iNKT) cells. To elucidate the precise role of iNKT cells in AD development of NC mice, we employed two distinct murine models of iNKT cell over-representation: Vβ8 TCR congenic and Vα14 TCR transgenic NC mice. We found that Vα14 TCR transgenic (Vα14^Tg) but not Vβ8 TCR congenic (Vβ8^Cg) NC mice exhibited reduced AD development, which was attributed to both quantitative and qualitative changes in iNKT cells such as a biased expansion of the double-negative iNKT subset. Adoptive transfer experiments confirmed that iNKT cells from Vα14^Tg mice but not from Vβ8^Cg mice were responsible for protecting NC mice from AD development. Double-negative iNKT cells from Vα14^Tg NC mice showed a T helper type-1‒dominant cytokine profile, which may account for the expansion of CD4⁺ regulatory T cells and memory-type CD8⁺ T cells. Furthermore, the adoptive transfer of CD8⁺ T cells from Vα14^Tg NC mice into AD-susceptible wild-type NC mice suppressed AD in recipient NC mice. Taken together, our results have identified double-negative iNKT cells as promising cellular targets to prevent AD pathogenesis.

Antibody-suppressor CD8+ T Cells Require CXCR5

BACKGROUND

We previously reported the novel activity of alloprimed CD8 T cells that suppress posttransplant alloantibody production. The purpose of the study is to investigate the expression and role of CXCR5 on antibody-suppressor CD8 T-cell function.

METHODS

C57BL/6 mice were transplanted with FVB/N hepatocytes. Alloprimed CD8 T cells were retrieved on day 7 from hepatocyte transplant recipients. Unsorted or flow-sorted (CXCR5CXCR3 and CXCR3CXCR5) alloprimed CD8 T-cell subsets were analyzed for in vitro cytotoxicity and capacity to inhibit in vivo alloantibody production following adoptive transfer into C57BL/6 or high alloantibody-producing CD8 knock out (KO) hepatocyte transplant recipients. Alloantibody titer was assessed in CD8 KO mice reconstituted with naive CD8 T cells retrieved from C57BL/6, CXCR5 KO, or CXCR3 KO mice. Antibody suppression by ovalbumin (OVA)-primed monoclonal OVA-specific t-cell receptor transgenic CD8+ T cells (OT-I) CXCR5 or CXCR3 CD8 T-cell subsets was also investigated.

RESULTS

Alloprimed CXCR5CXCR3CD8 T cells mediated in vitro cytotoxicity of alloprimed "self" B cells, while CXCR3CXCR5CD8 T cells did not. Only flow-sorted alloprimed CXCR5CXCR3CD8 T cells (not flow-sorted alloprimed CXCR3CXCR5CD8 T cells) suppressed alloantibody production and enhanced graft survival when transferred into transplant recipients. Unlike CD8 T cells from wild-type or CXCR3 KO mice, CD8 T cells from CXCR5 KO mice do not develop alloantibody-suppressor function. Similarly, only flow-sorted CXCR5CXCR3 (and not CXCR3CXCR5) OVA-primed OT-I CD8 T cells mediated in vivo suppression of anti-OVA antibody production.

CONCLUSIONS

These data support the conclusion that expression of CXCR5 by antigen-primed CD8 T cells is critical for the function of antibody-suppressor CD8 T cells.

Biological characteristics of intestinal IgE and gut diseases

Immunoglobulin E (IgE), a crucial protective substance for the intestinal tract, plays an important role in gut immunity. IgE is secreted by plasma cells in the submucosal lamina propria upon antigenic invasion and, together with certain cytokines and immune cells, is involved in the regulation of gastrointestinal immunity in normal or abnormal conditions via the high affinity IgE receptor (FcεR I) and low affinity IgE receptor (CD23⁺). In this paper, we review the structure, synthetic transport, secretory regulation, receptor classification, and function of intestinal IgE as well as the related gut diseases.

Critical role of NKT cells in posttransplant alloantibody production

We previously reported that posttransplant alloantibody production in CD8-deficient hosts is IL-4+ CD4+ T cell-dependent and IgG1 isotype-dominant. The current studies investigated the hypothesis that IL-4-producing natural killer T cells (NKT cells) contribute to maximal alloantibody production. To investigate this, alloantibody levels were examined in CD8-deficient WT, CD1d KO and Jα18 KO transplant recipients. We found that the magnitude of IgG1 alloantibody production was critically dependent on the presence of type I NKT cells, which are activated by day 1 posttransplant. Unexpectedly, type I NKT cell contribution to enhanced IgG1 alloantibody levels was interferon-γ-dependent and IL-4-independent. Cognate interactions between type I NKT and B cells alone do not stimulate alloantibody production. Instead, NKT cells appear to enhance maturation of IL-4+ CD4+ T cells. To our knowledge, this is the first report to substantiate a critical role for type I NKT cells in enhancing in vivo antibody production in response to endogenous antigenic stimuli.

Alloprimed CD8(+) T cells regulate alloantibody and eliminate alloprimed B cells through perforin- and FasL-dependent mechanisms

While it is well known that CD4(+) T cells and B cells collaborate for antibody production, our group previously reported that CD8(+) T cells down-regulate alloantibody responses following transplantation. However, the exact mechanism involved in CD8(+) T cell-mediated down-regulation of alloantibody remains unclear. We also reported that alloantibody production is enhanced when either perforin or FasL is deficient in transplant recipients. Here, we report that CD8(+) T cell-deficient transplant recipient mice (high alloantibody producers) exhibit an increased number of primed B cells compared to WT transplant recipients. Furthermore, CD8(+) T cells require FasL, perforin and allospecificity to down-regulate posttransplant alloantibody production. In vivo CD8-mediated clearance of alloprimed B cells was also FasL- and perforin-dependent. In vitro data demonstrated that recipient CD8(+) T cells directly induce apoptosis of alloprimed IgG1(+) B cells in co-culture in an allospecific and MHC class I-dependent fashion. Altogether these data are consistent with the interpretation that CD8(+) T cells down-regulate posttransplant alloantibody production by FasL- and perforin-dependent direct elimination of alloprimed IgG1(+) B cells.

Genome-wide association study for levels of total serum IgE identifies HLA-C in a Japanese population

Most of the previously reported loci for total immunoglobulin E (IgE) levels are related to Th2 cell-dependent pathways. We undertook a genome-wide association study (GWAS) to identify genetic loci responsible for IgE regulation. A total of 479,940 single nucleotide polymorphisms (SNPs) were tested for association with total serum IgE levels in 1180 Japanese adults. Fine-mapping with SNP imputation demonstrated 6 candidate regions: the PYHIN1/IFI16, MHC classes I and II, LEMD2, GRAMD1B, and chr13∶60576338 regions. Replication of these candidate loci in each region was assessed in 2 independent Japanese cohorts (n = 1110 and 1364, respectively). SNP rs3130941 in the HLA-C region was consistently associated with total IgE levels in 3 independent populations, and the meta-analysis yielded genome-wide significance (P = 1.07×10⁻¹⁰). Using our GWAS results, we also assessed the reproducibility of previously reported gene associations with total IgE levels. Nine of 32 candidate genes identified by a literature search were associated with total IgE levels after correction for multiple testing. Our findings demonstrate that SNPs in the HLA-C region are strongly associated with total serum IgE levels in the Japanese population and that some of the previously reported genetic associations are replicated across ethnic groups.

Selective induction of CTL helper rather than killer activity by natural epitope variants promotes dendritic cell-mediated HIV-1 dissemination

The ability of HIV-1 to rapidly accumulate mutations provides the virus with an effective means of escaping CD8(+) CTL responses. In this study, we describe how subtle alterations in CTL epitopes expressed by naturally occurring HIV-1 variants can result in an incomplete escape from CTL recognition, providing the virus with a selective advantage. Rather than paralyzing the CTL response, these epitope modifications selectively induce the CTL to produce proinflammatory cytokines in the absence of target killing. Importantly, instead of dampening the immune response through CTL elimination of variant Ag-expressing immature dendritic cells (DC), a positive CTL-to-DC immune feedback loop dominates whereby the immature DC differentiate into mature proinflammatory DC. Moreover, these CTL-programmed DC exhibit a superior capacity to mediate HIV-1 trans-infection of T cells. This discordant induction of CTL helper activity in the absence of killing most likely contributes to the chronic immune activation associated with HIV-1 infection, and can be used by HIV-1 to promote viral dissemination and persistence. Our findings highlight the need to address the detrimental potential of eliciting dysfunctional cross-reactive memory CTL responses when designing and implementing anti-HIV-1 immunotherapies.

Stepwise epigenetic and phenotypic alterations poise CD8+ T cells to mediate airway hyperresponsiveness and inflammation

The functional plasticity of CD8(+) T cells in an atopic environment, encompassing a spectrum from IFN-γ- to IL-13-producing cells, is pivotal in the development of allergic airway hyperresponsiveness and inflammation, and yet remains mechanistically undefined. We demonstrate that CD8(+) T cell IL-13 induction proceeded through a series of distinct IL-4/GATA3-regulated stages characterized by gene expression and epigenetic changes. In vivo, CD8(+) T cells exposed to an environment rich in IL-4 displayed epigenetic changes at the GATA3 and IL-13 promoter indicative of transcriptional activation and IL-13 production. In vitro, IL-4 triggered the stepwise molecular conversion of CD8(+) T cells from IFN-γ to IL-13 production. During the initial stage, IL-4 suppressed T-bet and induced GATA3 expression, characterized by enhanced activating histone modifications and RNA polymerase II (Pol II) recruitment to the GATA3 locus. Notably, recruitment of GATA3 and RNA Pol II to the IL-13 promoter was also detected at this initial stage. However, enhanced IL-13 transcription only occurred at a later stage after TCR stimulation, indicating that IL-4-induced GATA3 recruitment poises the IL-13 locus for TCR-mediated transcription. Thus, both in vivo and in vitro, an atopic (IL-4) environment poises CD8(+) T cells via stepwise epigenetic and phenotypic mechanisms for pathogenic conversion to IL-13 production, which is ultimately triggered via an allergen-mediated TCR stimulus.

Th17 responses in chronic allergic airway inflammation abrogate regulatory T-cell-mediated tolerance and contribute to airway remodeling

The role of T-helper type 17 (Th17) responses in airway remodeling in asthma is currently unknown. We demonstrate that both parenteral and mucosal allergen sensitization, followed by allergen inhalation, leads to Th17-biased lung immune responses. Unlike Th17 cells generated in vitro, lung Th17 cells did not produce tumor necrosis factor-α or interleukin (IL)-22. Eosinophilia predominated in acute inflammation, while neutrophilia and IL-17 increased in chronic disease. Allergen-induced tolerance involved Foxp3-, Helios-, and glycoprotein-A repetitions predominant-expressing regulatory T cells (Treg) and IL-10/interferon-γ priming. This Treg phenotype was altered in inflamed lungs and abrogated by inhalation of IL-17. Using Th17-deficient mice with genetic disruption of gp130 in T cells, we showed that Th17 cells induce airway remodeling independent of the Th2 response. All-trans retinoic acid administration ameliorated Th17-mediated disease and increased Treg activity, while dexamethasone inhibited eosinophilia but not neutrophilia, and enhanced Th17 development in vitro. Targeting the Th17/Treg axis might therefore be therapeutic in neutrophilic and glucocorticoid-refractory asthma.

An early reduction in Treg cells correlates with enhanced local inflammation in cutaneous leishmaniasis in CCR6-deficient mice

Resistance to Leishmania major infection is dependent on the development of a cell-mediated Th1 immune response in resistant C57BL/6 mice whereas Th2-prone BALB/c mice develop non-healing lesions after infection. The chemokine receptor CCR6 is shared by anti-inflammatory regulatory T cells and pro-inflammatory Th17 cells. In a recent study we showed that C57BL/6 mice deficient in CCR6 exhibited enhanced footpad swelling and impaired T helper cell migration indicated by reduced recruitment of total T helper cells into the skin after infection and a reduced delayed type hypersensitivity reaction. Based on these findings we tested whether the lack of CCR6 alters Treg or Th17 cell responses during the course of Leishmania major infection. When we analyzed T cell subsets in the lymph nodes of CCR6-deficient mice, Th17 cell numbers were not different. However, reduced numbers of Treg cells paralleled with a stronger IFNγ response. Furthermore, the early increase in IFNγ-producing cells correlated with increased local tissue inflammation at later time points. Our data indicate an important role of CCR6 for Treg cells and a redundant role for Th17 cells in a Th1 cell-driven anti-parasitic immune response against Leishmania major parasites in resistant C57BL/6 mice.

Immunotherapy of cancer in 2012

The immunotherapy of cancer has made significant strides in the past few years due to improved understanding of the underlying principles of tumor biology and immunology. These principles have been critical in the development of immunotherapy in the laboratory and in the implementation of immunotherapy in the clinic. This improved understanding of immunotherapy, enhanced by increased insights into the mechanism of tumor immune response and its evasion by tumors, now permits manipulation of this interaction and elucidates the therapeutic role of immunity in cancer. Also important, this improved understanding of immunotherapy and the mechanisms underlying immunity in cancer has fueled an expanding array of new therapeutic agents for a variety of cancers. Pegylated interferon-α2b as an adjuvant therapy and ipilimumab as therapy for advanced disease, both of which were approved by the United States Food and Drug Administration for melanoma in March 2011, are 2 prime examples of how an increased understanding of the principles of tumor biology and immunology have been translated successfully from the laboratory to the clinical setting. Principles that guide the development and application of immunotherapy include antibodies, cytokines, vaccines, and cellular therapies. The identification and further elucidation of the role of immunotherapy in different tumor types, and the development of strategies for combining immunotherapy with cytotoxic and molecularly targeted agents for future multimodal therapy for cancer will enable even greater progress and ultimately lead to improved outcomes for patients receiving cancer immunotherapy.

Probiotic modulation of dendritic cells co-cultured with intestinal epithelial cells

AIM: To investigate cytokine production and cell surface phenotypes of dendritic cells (DC) in the presence of epithelial cells stimulated by probiotics.

METHODS: Mouse DC were cultured alone or together with mouse epithelial cell monolayers in normal or inverted systems and were stimulated with heat-killed probiotic bacteria, Bifidobacterium lactis AD011 (BL), Bifidobacterium bifidum BGN4 (BB), Lactobacillus casei IBS041 (LC), and Lactobacillus acidophilus AD031 (LA), for 12 h. Cytokine levels in the culture supernatants were determined by enzyme-linked immunosorbent assay and phenotypic analysis of DC was investigated by flow cytometry.

RESULTS: BB and LC in single-cultured DC increased the expression of I-Ad, CD86 and CD40 (I-Ad, 18.51 vs 30.88, 46.11; CD86, 62.74 vs 92.7, 104.12; CD40, 0.67 vs 6.39, 3.37, P < 0.05). All of the experimental probiotics increased the production of inflammatory cytokines, interleukin (IL)-6 and tumor necrosis factor (TNF)-α. However, in the normal co-culture systems, LC and LA decreased the expression of I-A^d (39.46 vs 30.32, 33.26, P < 0.05), and none of the experimental probiotics increased the levels of IL-6 or TNF-α. In the inverted co-culture systems, LC decreased the expression of CD40 (1.36 vs -2.27, P < 0.05), and all of the experimental probiotics decreased the levels of IL-6. In addition, BL increased the production of IL-10 (103.8 vs 166.0, P < 0.05) and LC and LA increased transforming growth factor-β secretion (235.9 vs 618.9, 607.6, P < 0.05).

CONCLUSION: These results suggest that specific probiotic strains exert differential immune modulation mediated by the interaction of dendritic cells and epithelial cells in the homeostasis of gastrointestinal tract.

Allergen-specific CTL require perforin expression to suppress allergic airway inflammation

Allergen-specific CTL have a protective effect on allergic airway inflammation, a function thought to be mediated by cytokines, especially IFN-γ. However, the contribution of cytotoxic function to this protective effect has not been investigated. We examined the contribution of cytotoxic function to the therapeutic effect of allergen-specific CTL in allergic airway inflammation. We used a murine model of allergic airway inflammation in which mice were sensitized to OVA and then challenged with the same Ag via the intranasal route. CTL were elicited in these mice by immunization with dendritic cells (DC) or by adoptive transfer of in vitro-activated CD8(+) T cells. Hallmark features of allergic asthma, such as infiltration of eosinophils in the bronchoalveolar lavage fluid and mucus production, were assessed. Suppression of allergic airway inflammation by allergen-specific CTL was critically dependent on the expression of perforin, a key component of the cytotoxic machinery. Both perforin-sufficient and perforin-deficient allergen-specific CTL were recovered from the lungs of allergen-sensitized mice and upregulated CD69 expression and secreted the cytokines IFN-γ and TNF-α upon intranasal allergen challenge. However, only perforin-sufficient CTL inhibited eosinophil infiltration in the airway, mucus production, and cytokine accumulation in the bronchoalveolar lavage fluid. Treatment with allergen-specific CTL, but not their perforin-deficient counterparts, was also associated with a decrease in the number of DC in the mediastinal lymph node. Our data suggest that the cytotoxic function of allergen-specific CD8(+) T cells is critical to their ability to moderate allergic airway inflammation.

TLR1/2 activation during heterologous prime-boost vaccination (DNA-MVA) enhances CD8+ T Cell responses providing protection against Leishmania (Viannia)

BACKGROUND

Leishmania (Viannia) parasites present particular challenges, as human and murine immune responses to infection are distinct from other Leishmania species, indicating a unique interaction with the host. Further, vaccination studies utilizing small animal models indicate that modalities and antigens that prevent infection by other Leishmania species are generally not protective.

METHODOLOGY

Using a newly developed mouse model of chronic L. (Viannia) panamensis infection and the heterologous DNA prime - modified vaccinia virus Ankara (MVA) boost vaccination modality, we examined whether the conserved vaccine candidate antigen tryparedoxin peroxidase (TRYP) could provide protection against infection/disease.

RESULTS

Heterologous prime - boost (DNA/MVA) vaccination utilizing TRYP antigen can provide protection against disease caused by L. (V.) panamensis. However, protection is dependent on modulating the innate immune response using the TLR1/2 agonist Pam3CSK4 during DNA priming. Prime-boost vaccination using DNA alone fails to protect. Prior to infection protectively vaccinated mice exhibit augmented CD4 and CD8 IFNγ and memory responses as well as decreased IL-10 and IL-13 responses. IL-13 and IL-10 have been shown to be independently critical for disease in this model. CD8 T cells have an essential role in mediating host defense, as CD8 depletion reversed protection in the vaccinated mice; vaccinated mice depleted of CD4 T cells remained protected. Hence, vaccine-induced protection is dependent upon TLR1/2 activation instructing the generation of antigen specific CD8 cells and restricting IL-13 and IL-10 responses.

CONCLUSIONS

Given the general effectiveness of prime-boost vaccination, the recalcitrance of Leishmania (Viannia) to vaccine approaches effective against other species of Leishmania is again evident. However, prime-boost vaccination modality can with modulation induce protective responses, indicating that the delivery system is critical. Moreover, these results suggest that CD8 T cells should be targeted for the development of a vaccine against infection caused by Leishmania (Viannia) parasites. Further, TLR1/2 modulation may be useful in vaccines where CD8 T cell responses are critical.

Human CD8⁺ T cells drive Th1 responses through the differentiation of TNF/iNOS-producing dendritic cells

TNF/iNOS-producing dendritic cells (Tip-DCs) have been shown to arise during inflammation and are important mediators of immune defense. However, it is still relatively unclear which cell types contribute to their differentiation. Here we show that CD8(+) T cells, through the interaction with DCs, can induce the rapid development of human monocytes into Tip-DCs that express high levels of TNF-α and iNOS. Tip-DCs exhibited T-cell priming ability, expressed high levels of MHC class II, upregulated co-stimulatory molecules CD40, CD80, CD86, toll-like receptors TLR2, TLR3, TLR4, chemokine receptors CCR1 and CX3CR1 and expressed the classical mature DC marker, CD83. Differentiation of monocytes into Tip-DCs was partially dependent on IFN-γ as blocking the IFN-γ receptor on monocytes resulted in a significant decrease in CD40 and CD83 expression and in TNF-α production. Importantly, these Tip-DCs were capable of further driving Th1 responses by priming naive CD4(+) T cells for proliferation and IFN-γ production and this was partially dependent on Tip-DC production of TNF-α and NO. Our study hence identifies a role for CD8(+) T cells in orchestrating Th1-mediating signals through the differentiation of monocytes into Th1-inducing Tip-DCs.

Expansion of regulatory CD8+ CD25+ T cells after neonatal alloimmunization

Transplantation tolerance induced by neonatal injection of semi-allogeneic spleen cells is associated with a pathological syndrome caused by T helper type 2 (Th2) differentiation of donor-specific CD4(+) T lymphocytes. We have shown previously that this Th2-biased response is inhibited by host CD8(+) T cells. Herein, we demonstrate that upon neonatal immunization with (A/J × BALB/c)F(1) spleen cells, BALB/c mice expand a population of CD8(+) T cells expressing both CD25 and forkhead box P3 (FoxP3) markers. In this setting, CD8(+) CD25(+) T cells predominantly produce interferon (IFN)-γ and interleukin (IL)-10 and are efficient in controlling IL-4, IL-5 and IL-13 production by donor-specific CD4(+) T cells in vitro. CD8(+) FoxP3(-) T cells are single producers of IFN-γ or IL-10, whereas CD8(+) FoxP3(+) T cells are double producers of IFN-γ and IL-10. We further demonstrate that IFN-γ and IL-10 are two major cytokines produced by CD8(+) T cells involved in the in vivo regulation of Th2-type pathology. In this setting, we conclude that neonatal alloimmunization induces the expansion of several regulatory CD8(+) T cells which may control Th2 activities via IFN-γ and IL-10.

CD8+ T cells negatively regulate IL-4-dependent, IgG1-dominant posttransplant alloantibody production

We have previously reported that CD8(+) T cells significantly influence Ab production based on the observation that posttransplant alloantibody levels in CD8-deficient murine hepatocyte transplant recipients are markedly enhanced. However, the precise mechanisms contributing to enhanced alloantibody production in the absence of CD8(+) T cells is not understood. We hypothesized that alloactivated CD8(+) T cells inhibit Ab production by skewing toward a proinflammatory cytokine profile, whereas when these cells are absent, an anti-inflammatory cytokine profile shifts the alloimmune response toward alloantibody production. To investigate this possibility, alloantibody isotype profiles were examined in CD8-deficient and wild-type hepatocyte recipients. We found that IgG1 (IL-4-dependent isotype) was the dominant alloantibody isotype in wild-type recipients as well as in CD8-deficient recipients, although the amount of alloantibody in the latter group was substantially higher. Utilizing real-time PCR we found that CD4(+) T cells from wild-type recipients significantly upregulated IFN-γ but not IL-4 mRNA. In contrast, in the absence of CD8(+) T cells, CD4(+) T cells switched to significantly upregulate IL-4 mRNA, while IFN-γ was downregulated. IL-4 knockout mice do not produce any posttransplant alloantibody. However, adoptive transfer of wild-type CD4(+) T cells into CD8-depleted IL-4 knockout mice restores high alloantibody levels observed in CD8-depleted wild-type recipients. This suggests that IL-4-producing CD4(+) T cells are critical for posttransplant alloantibody production. Additionally, this CD8-mediated regulation of posttransplant alloantibody production is IFN-γ-dependent. Further elucidation of the mechanisms by which CD8(+) T cells influence Ab production will significantly contribute to development of therapies to manipulate humoral responses to Ag.

Understanding the genetic regulation of IgE production

Immunoglobulin E (IgE) is a key mediator of anti-parasitic and anti-tumour immunity. However it is also a critical component of atopic and autoimmune diseases, and elevated serum IgE levels are a common indicator of immune dysregulation. In this review we survey the literature on genetic associations of elevated IgE in humans and mice. We find that defects in a limited number of pathways explain the majority of gene associations with IgE. Commonly, elevated IgE is associated with defects in Th bias and B cell class switching, severe T cell tolerance defects and defects in immunity at the host-environment interface. These genetic data demonstrate the mechanisms of control over IgE production and the manner in which they can be circumvented.

Regulation of Th2 responses and allergic inflammation through bystander activation of CD8+ T lymphocytes in early life

Th2-biased immune responses characterizing neonates may influence the later onset of allergic disease. The contribution of regulatory T cell populations in the prevention of Th2-driven pathologies in early life is poorly documented. We investigated the potential of CD8(+) T cells stimulated at birth with alloantigens to modulate the development of allergic airway inflammation. Newborn mice were immunized with semiallogeneic splenocytes or dendritic cells (DCs) and exposed at the adult stage to OVA aeroallergens. DC-immunized animals displayed a strong Th1 and Tc1/Tc2 alloantigen-specific response and were protected against the development of the allergic reaction with reduced airway hyperresponsiveness, mucus production, eosinophilia, allergen-specific IgE and IgG(1), and reduction of lung IL-4, IL-5, IL-10, and IL-13 mRNA levels. By contrast, splenocyte-immunized mice displayed a Th2 and a weak Tc2 alloantigen-specific response and were more sensitive to the development of the allergen-specific inflammation compared with mice unexposed at birth to alloantigens. DC-immunized animals displayed an important increase in the percentage of IFN-gamma-producing CD8(+)CD44(high), CD8(+)CD62L(high), and CD8(+)CD25(+) subsets. Adoptive transfers of CD8(+) T cells from semiallogeneic DC-immunized animals to adult beta(2)m-deficient animals prevented the development of allergic response, in particular IgE, IL-4, and IL-13 mRNA production in an IFN-gamma-dependent manner, whereas transfers of CD8(+) T cells from semiallogeneic splenocyte-immunized mice intensified the lung IL-4 and IL-10 mRNA level and the allergen-specific IgE. These findings demonstrated that neonatal induction of regulatory CD8(+) T cells was able to modulate key parameters of later allergic sensitization in a bystander manner, without recognition of MHC class I molecules.

Polarized dendritic cells as cancer vaccines: directing effector-type T cells to tumors

Ex vivo generation and antigen loading of dendritic cells (DCs) from cancer patients helps to bypass the dysfunction of endogenous DCs. It also allows to control the process of DC maturation and to imprint in maturing DCs several functions essential for induction of effective forms of cancer immunity. Recent reports from several groups including ours demonstrate that distinct conditions of DC generation and maturation can prime DCs for preferential interaction with different (effector versus regulatory) subsets of immune cells. Moreover, differentially-generated DCs have been shown to imprint different effector mechanisms in CD4(+) and CD8(+) T cells (delivery of "signal three") and to induce their different homing properties (delivery of "signal four"). These developments allow for selective induction of tumor-specific T cells with desirable effector functions and tumor-relevant homing properties and to direct the desirable types of immune cells to tumors.

Dendritic cell-based therapeutic cancer vaccines: what we have and what we need

Therapeutic cancer vaccines rely on the immune system to eliminate tumor cells. In contrast to chemotherapy or passive (adoptive) immunotherapies with antibodies or ex vivo-expanded T cells, therapeutic vaccines do not have a direct anti-tumor activity, but aim to reset patients' immune systems to achieve this goal. Recent identification of effective ways of enhancing immunogenicity of tumor-associated antigens, including the use of dendritic cells and other potent vectors of cancer vaccines, provide effective tools to induce high numbers of circulating tumor-specific T cells. However, despite indications that some of the new cancer vaccines may be able to delay tumor recurrence or prolong the survival of cancer patients, their ability to induce cancer regression remains low. Recent reports help to identify and prospectively remove the remaining obstacles towards effective therapeutic vaccination of cancer patients. They indicate that the successful induction of tumor-specific T cells by cancer vaccines is not necessarily associated with the induction of functional cytotoxic T lymphocytes, and that current cancer vaccines may promote undesirable expansion of Treg cells. Furthermore, recent studies also identify the tools to counteract such phenomena, in order to assure the desirable induction of Th1-cytotoxic T lymphocytes, NK-mediated type-1 immunity and appropriate homing of effector cells to tumors.

CD44high memory CD8 T cells synergize with CpG DNA to activate dendritic cell IL-12p70 production

Protective memory CD8 T cell responses are generally associated with the rapid and efficient acquisition of CTL function. However, the ability of memory CD8 T cells to modulate immune responses through interactions with dendritic cells (DCs) during the early states of secondary Ag exposure is poorly understood. In this study, we show that murine Ag-specific CD44(high) CD8 T cells, representing CD8 T cells of the memory phenotype, potently activate DCs to produce high levels of IL-12p70 in conjunction with stimulation of DCs with the TLR 9 ligand, unmethylated CpG DNA. IL-12p70 production was produced predominantly by CD8alpha(+) DCs and plasmacytoid DCs, and mediated by CD8 T cell-derived cytokines IFN-gamma, GM-CSF, TNF-alpha, and surface CD40L. We also find that CD44(high) memory phenotype CD8 T cells were better DC IL-12p70 stimulators than CD44(low) naive phenotype CD8 T cells, and this was attributed to higher levels of IFN-gamma and GM-CSF produced by CD44(high) memory phenotype CD8 T cells during their Ag specific interaction with DCs. Our study identifies CpG DNA as the most effective TLR ligand that cooperates with CD8 T cells for DC IL-12p70 production, and suggests that effectiveness of memory CD8 T cells could be attributed to their ability to rapidly and effectively induce protective Th1 immunity during early stages of pathogen reinfection.

Suppression of allergic airway inflammation and IgE responses by a class I restricted allergen peptide vaccine

CD8 T cells are known to deviate CD4 T-cell responses from Th2 toward Th1. Reduction of Th2 cytokines and increased interferon-gamma ameliorates allergic airway disease. We have developed a novel approach to the suppression of allergic airway inflammation, by designing a MHC class I-restricted allergen peptide vaccine, which induces potent and long-lived CD8 T-cell responses. Vaccination of C57BL/6 mice before allergen sensitization completely prevented allergen-specific immunoglobulin E (IgE) antibody responses. Vaccination after sensitization failed to suppress IgE, but inhibited accumulation of eosinophils and neutrophils in airways after subsequent allergen challenge. Vaccination suppressed Th2 airway infiltration and enhanced the lung Th1 response without inducing excessive CD8 cellular infiltration or interleukin-17, and the combination of class I peptide with adjuvant was more effective than adjuvant alone. Airway hyperreactivity was prevented by vaccination in an allergen-specific fashion. Class I peptide vaccines might therefore represent a robust and long-lasting immunotherapeutic strategy in allergic disease.

Improvement of adaptive immunity by antigen-carrying biodegradable nanoparticles

One of the most important aspects in vaccine development is to induce potent antigen-specific immune responses. In this study, we examined the immunological activities of antigen-carrying biodegradable poly(gamma-glutamic acid) (gamma-PGA) nanoparticles (NPs) in mice. The immunization with ovalbumin (OVA)-carrying gamma-PGA NPs (OVA-NPs) could induce significant expansion of antigen-specific CD8(+) T cells. Unlike complete Freund's adjuvant, subcutaneous (s.c.) inoculation of OVA-NPs to footpad did not generate injection site swelling. Although OVA-NPs could induce both antigen-specific cellular and humoral immune responses, the dominant induction of either cellular or humoral immunity was found to depend on their administration routes. Strong antibody production was observed by s.c. immunization, yet no antibody was identified by intranasal immunization. Thus, gamma-PGA NPs are a safe and efficient antigen carrier with unique immunological properties.

CD8+ T cells in asthma: friend or foe?

While it is well established that CD4(+) T lymphocytes play a crucial role in the initiation, progression and persistence of asthma, the role of CD8(+) T cells is less understood. CD8(+) T cells form functionally similar subsets which exhibit similar cytokine profiles as Th1 and Th2 cells, known as Tc1 and Tc2. Evidence from animal studies suggest that CD8(+) T cells are capable of regulating IgE production through the induction of IL-12 and IL-18 production in dendritic cells, and that CD8(+) T cells may act to moderate Th2 polarisation within the localised lymph nodes during allergic sensitisation. Such findings have led to the suggestion that Th1 polarising, CD8(+) T cell-inducing vaccines would inhibit the development of airway hyperresponsiveness (AHR) and Th2 cell infiltration. Despite these positive findings, the role of CD8(+) T cells within the lung remains poorly understood. While CD8(+) T cells, particularly those expressing the Tc1 phenotype, are capable of moderating inflammation and suppressing AHR, it has been postulated that Tc2 CD8(+) T cells predominate within established asthma and may act to amplify the inappropriate immune response which defines the condition. Within the clinic, the association between CD8(+) T cells and asthma is almost universally defined as injurious, further suggesting a prejudicial role for these cells within the established disease. CD8(+) T cells may be a valuable potential target for therapeutic intervention, either by potentiating their regulatory effects prior to the development of sensitisation, or through suppressing their pro-inflammatory properties within established atopy.

CD40L-expressing CD8 T cells prime CD8alpha(+) DC for IL-12p70 production

CD8alpha(+) DC are implicated as the principle DC subset for cross-presentation and cross-priming of cytotoxic CD8 T cell responses. In this study, we demonstrate another unique facet of the CD8alpha(+) DC and CD8 T cell relationship, by showing that CD8 T cells reciprocally activate CD8alpha(+) DC, but not CD8alpha(-) DC, for IL-12p70 production, the key Th1-promoting cytokine. This effect was observed during an antigen-specific interaction between DC and activated CD8 T cells, along with secondary TLR stimulation of DC by LPS. Activated CD8 T cells use a combination of IFN-gamma and CD40L, which is rapidly up-regulated post-stimulation, to prime DC for IL-12p70 production during an antigen-specific response. Our results suggest that the interaction between CD8alpha(+) DC and antigen-primed CD8 T cells may form an important component of Th1-mediated immunity through the induction of IL-12p70.

Memory CD8+ T cells protect dendritic cells from CTL killing

CD8(+) T cells have been shown to be capable of either suppressing or promoting immune responses. To reconcile these contrasting regulatory functions, we compared the ability of human effector and memory CD8(+) T cells to regulate survival and functions of dendritic cells (DC). We report that, in sharp contrast to the effector cells (CTLs) that kill DCs in a granzyme B- and perforin-dependent mechanism, memory CD8(+) T cells enhance the ability of DCs to produce IL-12 and to induce functional Th1 and CTL responses in naive CD4(+) and CD8(+) T cell populations. Moreover, memory CD8(+) T cells that release the DC-activating factor TNF-alpha before the release of cytotoxic granules induce DC expression of an endogenous granzyme B inhibitor PI-9 and protect DCs from CTL killing with similar efficacy as CD4(+) Th cells. The currently identified DC-protective function of memory CD8(+) T cells helps to explain the phenomenon of CD8(+) T cell memory, reduced dependence of recall responses on CD4(+) T cell help, and the importance of delayed administration of booster doses of vaccines for the optimal outcome of immunization.

Helper function of memory CD8+ T cells: heterologous CD8+ T cells support the induction of therapeutic cancer immunity

In contrast to the well-established efficacy of preventive vaccines, the effectiveness of therapeutic vaccines remains limited. To develop effective vaccination regimens against cancer, we have analyzed the effect of effector and memory CD8+ T cells on the ability of dendritic cells to mediate the immunologic and antitumor effects of vaccination. We show that in contrast to effector CD8+ T cells that kill antigen-carrying dendritic cells, IFNgamma-producing memory CD8+ T cells act as "helper" cells, supporting the ability of dendritic cells to produce interleukin-12 (IL-12) p70. Promoting the interaction of tumor antigen-carrying dendritic cells with memory-type "heterologous" (tumor-irrelevant) CD8+ T cells strongly enhances the IL-12p70-dependent immunogenic and therapeutic effects of vaccination in the animals bearing established tumors. Our data show that the suppressive and helper functions of CD8+ T cells are differentially expressed at different phases of CD8+ T-cell responses. Selective performance of helper functions by memory (in contrast to effector) CD8+ T cells helps to explain the phenomenon of immune memory and facilitates the design of effective therapeutic vaccines against cancer and chronic infections.

Dynamic imaging of chemokine-dependent CD8+ T cell help for CD8+ T cell responses

Naive T lymphocytes move efficiently in lymphoid tissues while scanning dendritic cells in search of cognate complexes of peptide in major histocompatibility molecules. However, T cell migration ceases after recognition of cognate antigen. We show here that during the initiation of antigen-specific CD8(+) T cell responses, naive CD8(+) polyclonal T cells 'preferentially' interacted in an antigen-independent way with mature dendritic cells competent to present antigen to antigen-specific CD8(+) T cells. These antigen-independent interactions required expression of the chemokine receptor CCR5 on polyclonal T cells and increased the efficiency of the induction of naive, low-precursor-frequency CD8(+) T cell responses. Thus, antigen-specific CD8(+) T cells favor the priming of naive CD8(+) T cells by promoting the CCR5-dependent recruitment of polyclonal CD8(+) T cells to mature dendritic cells.

Enhancement of IFN-gamma production for Th1-cell therapy using negatively charged liposomes containing phosphatidylserine

We have developed an efficient method of interferon-gamma (IFN-gamma) induction for Th1-cell therapy. OVA (ovalbumin)-specific Th1 clone 42-6A cells cocultured with antigen presenting cells (APCs) from spleen resulted in high levels of OVA-specific IFN-gamma production by the treatment of phosphatidylserine (PS), but not phosphatidic acid (PA), liposomes-encapsulated OVA (OVA-liposomes). The IFN-gamma production was increased in a manner dependent on the PS content of the liposomes and inhibited by the addition of annexin V, a PS binding protein. Furthermore, coadministration of Th1 cells plus OVA-liposomes in mice strikingly enhanced IFN-gamma levels in serum and in spleen cells compared with that of Th1 cells plus OVA. In addition, serum levels of IL-12 p70 increased and ongoing OVA-specific IgE immune response was dramatically attenuated. These results first suggest that antigen delivery using negatively charged liposomes containing PS is very useful for the enhancement of IFN-gamma production in Th1-cell therapy.

An essential role for IL-18 in CD8 T cell-mediated suppression of IgE responses

The ability of CD8 T cells to suppress IgE responses is well established. Previously, we demonstrated that CD8 T cells inhibit IgE responses via the induction of IL-12, which promotes Th1 and suppresses Th2 responses. In this study, we show that IL-18 also plays an essential role in IgE suppression. In vitro, IL-18 synergized with IL-12 to promote Th1/T cytotoxic 1 and inhibit Th2/T cytotoxic 2 differentiation. OVA-specific TCR transgenic (OT-I) CD8 cells induced both IL-12 and IL-18 when cultured with OVA(257-264) peptide-pulsed dendritic cells. In vivo, IL-18(-/-) mice exhibited higher IgE and IgG1 levels compared with wild-type mice after immunization with OVA/alum. Furthermore, adoptive transfer of CD8 T cells from OVA-primed mice suppressed IgE responses in OVA/alum-immunized mice, but not in IL-18(-/-) mice. IgE suppression in IL-18(-/-) mice was restored if CD8 T cells were coadoptively transferred with IL-18-competent wild-type bone marrow dendritic cell progenitors, demonstrating an essential role of IL-18 in CD8 T cell-mediated suppression of IgE responses. The data suggest that CD8 T cells induce IL-18 production during a cognate interaction with APCs that synergizes with IL-12 to promote immune deviation away from the allergic phenotype. Our data identify IL-18 induction as a potentially useful target in immunotherapy of allergic disease.

Characterization of the antigenic specificity of soybean protein β-conglycinin and its effects on growth and immune function in rats

The objective of the present study was to characterize the antigenic specificity of purified soybean beta-conglycinin and to investigate its effects on the growth and immune responses of rats. Thirty-two Brown Norway rats, 3 weeks of age, were randomly allotted to one of four treatments and individually fed casein-cornstarch based diets. Rats were sensitised by means of intragastric gavage with purified beta-conglycinin (0, 5, 10 or 20 mg protein/ml in phosphate buffered saline at pH 7.4) on day 0, 7, 14, and 21 (1 ml/animal). On day 28, rats received a double dose of beta-conglycinin. Blood was obtained at weekly intervals after initiation of challenge. Growth declined linearly with increasing the concentration of soybean beta-conglycinin (p < 0.05). Both the total IgE and beta-conglycinin-specific IgE levels in serum increased while passive cutaneous anaphylactic reactions were induced in the rats. Lymphocyte proliferation response to concanavalin A in plasma and spleen was increased linearly with increased levels of soybean (p < 0.01) beta-conglycinin. The percentage of CD4+ lymphocyte subset linearly increased (p < 0.001). As a result, the concentrations of cytokines in plasma and spleen, including interleukin-4 (p < 0.01), interleukin-5 (p < 0.01), and tumour necrosis factor-alpha (p < 0.01) increased linearly with increasing level of purified beta-conglycinin. Our results indicate that purified beta-conglycinin possesses intrinsic immune-stimulating capacity and can induce an allergic reaction. Therefore, dietary soybean beta-conglycinin has negative effects on growth and both cell-mediated and humoral immune function in rats.

Research advances in the imbalance of helper T lymphocyte subpopulations and cytokine network in patients with chronic hepatitis B

Helper T (Th) lymphocytes, important immune regulating cells of organism, could be divided into four functional subsets, Th0, Th1, Th2, Th3, on the basis of the immunoregulatory cytokines that these clones produced. Most of the current work in this field is exploratory and focuses on Th1 and Th2 subsets. Th1 cells secrete interferon-γ (IFN-γ), interkeukin-2 (IL-2) and tumor necrosis factor-β and are principally involved in cell-mediated immunity. They play an important role in the protection against intracellular pathogens, including a variety of viruses. Th2 cells secret interleukin-4 (IL-4), IL-5, IL-6 and IL-10 and regulate the humoral immune response. Th0 cells are naive Th cells, secreting Th1/Th2 phenotype cytokines at low levels. However, Th3 cells, which secrete active transforming growth factor-β, exert a negative immunoregulatory action on the immune response. The cross-regulatory properties of Th1 and Th2 subset cells and relevant cytokines network are very important to maintain normal immunity of organisms. HBV can destroy the balance of Th lymphocytes and cytokines network. The imbalance of pro-inflammatory Th1 and anti-inflammatory Th2 cytokine production play an important role in the immunopathogenesis of hepatitis B virus infection and alter chronic liver disease development, progression and outcome.

Regulation of allergic airway inflammation by class I-restricted allergen presentation and CD8 T-cell infiltration

BACKGROUND

CD8 T cells are known to respond to exogenous antigens through cross-presentation. The importance of the CD8 cell response in the lung after inhalation of allergen and its effects on asthmatic inflammation are less clear.

OBJECTIVE

We sought to determine the dynamics, nature, and immunoregulatory activities of the class I CD8 T-cell response to inhaled allergen.

METHODS

We studied a murine model of respiratory allergen sensitization, adoptive transfer of transgenic T cells, and flow cytometric analysis of lung infiltrates.

RESULTS

Class I-restricted CD8 T cells responded rapidly to inhaled allergen and dominated the acute infiltration of T cells into the lung after secondary exposure. CD8 cells in the lung expressed a type 1 phenotype and suppressed the systemic IgE response to subsequent immunization. Dendritic cells purified from conducting airways or lung tissue were highly efficient at cross-presentation of antigen into the class I pathway after intranasal challenge. Adoptive transfer of transgenic antigen-specific CD8, but not CD4, cells resulted in increased IL-12 levels and reduced IL-13 and IL-5 levels in bronchoalveolar lavage fluid, coupled with substantially reduced airway eosinophilia after repeated allergen inhalation, a process mimicked by intranasal administration of IL-12 and inhibited by anti-IL-12 antibody.

CONCLUSION

The data suggest that CD8 cells specific for inhaled allergens are generated in draining lymph nodes but suppress allergic airway inflammation through induction of IL-12 in the lung during interaction with respiratory dendritic cells.

CLINICAL IMPLICATIONS

Novel peptide immunotherapeutics targeting the class I-restricted CD8 T-cell response to allergen represent a promising strategy for extrinsic asthma.

Hypersensitivity reaction against influenza vaccine in a patient with rheumatoid arthritis after the initiation of etanercept injections

A 58-year-old Japanese woman with rheumatoid arthritis (RA) suffered from high fever triggered by administration of an influenza vaccine after a 4-month-long effective treatment course with the TNF-alpha inhibitor etanercept. Influenza vaccine had been previously administrated safely to the patient before initiation of etanercept therapy. The fever occurred without other symptoms soon after vaccine administration, progressed to high fever 1 day later, and spontaneously resolved the second day. The clinical course appears to be compatible with drug fever closely associated with immediate hypersensitivity (in particular, late-phase type I allergic reaction), in which T helper (Th) 2 cells play a crucial role. Etanercept can strongly suppress Th1-mediated reactions; therefore, Th2 activity may be augmented by etanercept treatment in aspect of antagonism between Th1 and Th2 mechanisms. In RA patients who receive treatment with TNF-alpha inhibitor such as etanercept, activation of Th2-mediated immune responses such as immediate hypersensitivity may be a necessary side effect for those who receive vaccinations.

Is Genetic Vaccination against Allergy Possible?

Genetic immunization has proven a powerful method to induce antiallergic immune responses. The underlying functional principle has been described to be based on the recruitment of allergen-specific Th1 cells, CD8+ cells and the establishment of a Th1 cytokine milieu, which prevent the development of a Th2-biased response in a protective setup and can balance an ongoing Th2-type response in a therapeutic situation. Genetic immunization with plasmid DNA offers innovative solutions to the major problems associated with protein immunization, such as crosslinking of pre-existing immunoglobulin E on mast cells/basophils or induction of de novo synthesis of immunoglobulin E by the protein immunization itself. It easily enables the routine production of hypoallergenic vaccines, which do not translate native allergens, thus avoiding potential anaphylactic side effects. DNA vaccines can also be applied as mixtures of single vaccines, making them interesting candidates for treatment based on component-resolved diagnosis, followed by an individualized therapy with the relevant allergens. In addition to the description of up-to-date allergen gene vaccine approaches, this review gives an overview of animal studies dealing with the following topics: danger signals as the inherent adjuvant properties, methods to optimize the vaccine immunogenicity, modulation of the immune response, nonparenteral applications and low-dose vaccination strategies.

Cytokine-induced IL-10-secreting CD8 T cells represent a phenotypically distinct suppressor T-cell lineage

Populations of regulatory T cells (Tregs) control autoimmune and allergic immunopathology induced by self or foreign antigens. Several types of CD4(+) MHC class II-restricted Treg populations have been characterized, but the biology of CD8(+), MHC class I-restricted Tregs is less understood. We show here that CD8(+) Tregs are rapidly generated in the presence of IL-4 and IL-12, produce IL-10, and exhibit a unique cell-surface phenotype with coexpression of activation and naive cell-associated markers. They block activation of naive or effector T cells and suppress IgG/IgE antibody responses and graft-versus-host disease in vivo. Suppression is dependent on cell contact and mediated by direct T-cell-T-cell interaction that antagonizes T-cell-receptor (TCR) signals. The data establish the existence of a CD8 T-cell suppressor effector subset distinct in both phenotype and function from T cytotoxic 1 (Tc1) and Tc2 cells. Production of such CD8 Tregs has potential for cell-based therapy of CD4 or CD8 T-cell-mediated disease.

CD8+ T-cell-mediated killing of donor dendritic cells prevents alloreactive T helper type-2 responses in vivo

Accumulating evidence indicates that, in absence of CD8+ T-cell activation, CD4+ T-cell-mediated allograft rejection is associated with a dominant Th2-cell response and eosinophil infiltrates. In this study, we analyzed the mechanisms by which CD8+ T cells regulate alloreactive CD4+ T-cell priming and differentiation into interleukin 4 (IL-4)-producing cells. We showed that interferon gamma (IFN-gamma) production by CD8+ T cells was dispensable for the inhibition of Th2-cell development, as well as tissue eosinophilia and type 2 cytokine production in the rejected grafts. Since we noticed that CD8+ T cells not only suppressed Th2 differentiation, but also down-modulated the overall priming of alloreactive CD4+ T cells, we evaluated whether CD8+ T cells act by limiting the accumulation of donor-derived dendritic cells (DCs) in lymph nodes. We found that indeed, alloreactive CD8+ T cells rapidly eliminated allogeneic DCs from T-cell areas of draining lymph nodes, through a perforin-dependent mechanism. Thus, our data demonstrate that cytotoxic T lymphocyte (CTL)-mediated clearance of allogeneic DCs is a negative feedback mechanism that limits the duration of alloantigen presentation in draining lymph nodes, thereby modulating the amplitude and polarization of the primary alloreactive CD4+ T-cell responses.

Prevention of allergy by a recombinant multi-allergen vaccine with reduced IgE binding and preserved T cell epitopes

Novel approaches for the prevention of allergy are required, because of the inevitably increasing prevalence of allergic diseases during the last 30 years. Here, a recombinant chimeric protein, which comprises the whole amino acid sequences of three bee venom major allergens has been engineered and used in prevention of bee venom sensitization in mice. Phospholipase A2 (Api m 1), hyaluronidase (Api m 2) and melittin (Api m 3) fragments with overlapping amino acids were assembled in a different order in the Api m (1/2/3) chimeric protein, which preserved entire T cell epitopes, whereas B cell epitopes of all three allergens were abrogated. Accordingly, IgE cross-linking leading to mast cell and basophil mediator release was profoundly reduced in humans. Supporting these findings, the Api m (1/2/3) induced 100 to 1000 times less type-1 skin test reactivity in allergic patients. Treatment of mice with Api m (1/2/3) led to a significant reduction of specific IgE development towards native allergen, representing a protective vaccine effect in vivo. These results demonstrate a novel prototype of a preventive allergy vaccine, which preserves the entire T cell epitope repertoire, but bypasses induction of IgE against native allergen, and side effects related to mast cell/basophil IgE FcepsilonRI cross-linking in sensitized individuals.

Regulatory Role of Host CD8+ T Lymphocytes in Experimental Graft-versus-Host Disease across a Single Major Histocompatibility Complex Class II Incompatibility

BACKGROUND

CD8+ T cells are known to regulate type 2 helper T cell (Th2) alloreactive immune responses but their mode of activation is unclear. We investigated the role of host CD8+ T cells in experimental Th2-type graft-versus-host disease (GVHD) where donor/recipient disparity is restricted to a single major histocompatibility complex (MHC) class II antigen.

METHODS

Immunoglobulin (Ig) E serum levels, eosinophilia and lymphoid tissue hyperplasia were compared after injection of bm12 CD4+ T cells in either wild-type or CD8+ T cell-deficient (CD8-/-) C57BL/6 mice. In vitro, we explored effects of the addition of CD8+ T cells from wild-type or IFN-gamma-/- mice in mixed leukocyte cultures prepared with beta2 microglobulin-deficient (beta2m-/-) CD4+ T cells as responders or beta2m dendritic cells as stimulators.

RESULTS

HyperIgE resolved after 3 weeks in wild-type hosts whereas it persisted for 6 weeks in CD8-/- hosts. Eosinophil infiltrates in lymph nodes were significantly enhanced in CD8-/- hosts. Increased serum levels of IL-5 and IL-13 in CD8-/- hosts confirmed the enhancement of Th2-type responses in the context of recipient CD8+ T cell deficiency. Hyperplasia of lymph nodes and spleen were similar in both groups, as well as in vivo proliferation of donor CD4+ T cells. In vitro, CD8+ T cell regulation of the alloreactive Th2 response depended on their production of IFN-gamma and did not require expression of beta2m on CD4+ T cells or antigen-presenting cells.

CONCLUSIONS

Host CD8+ T cells regulate alloreactive Th2 responses during graft-versus-host disease through an IFN-gamma dependent pathway, independently of the recognition of beta2m-associated MHC class I molecules.

Activation of CD8+ regulatory T cells by human placental trophoblasts

The immunological basis by which a mother tolerates her semi-allogeneic fetus remains poorly understood. Several mechanisms are likely to contribute to this phenomenon including active immune regulation by regulatory T cells. In this article, we report that human placental trophoblasts activate a clonal population of CD8(+) T cells with regulatory function. These cells are not MHC class I restricted, but require costimulation through a member of the carcinoembryonic Ag family present on early gestation trophoblasts. These regulatory T cells express the mucosal markers CD101 and CD103 and display selective usage of the TCR gene Vbeta9. CD8(+) T cells isolated from the peripheral blood of pregnant mothers (16-28 wk) also demonstrate expansions in the same Vbeta family (Vbeta9), signaling a possible role for these cells in preventing fetal rejection in vivo. We have previously characterized a subset of CD8(+) regulatory T cells activated by the combination of the nonclassical class I molecule CD1d and a costimulatory molecule of the carcinoembryonic Ag family present on the intestinal epithelium. These data support the concept that distinct regulatory T cell populations exist at different sites and may be regulated locally by unique restriction elements, costimulatory signals, and Ags.

Consensual immunity: success-driven development of T-helper-1 and T-helper-2 responses

Non-germline-encoded T- and B-cell receptors allow humans to effectively deal with rapidly mutating pathogens. Here, we argue that, in addition to determining the antigenic specificity of immune responses, the same receptor systems can also regulate the T-helper-1/T-helper-2 profile of immunity. Such a mechanism--based on feedback from distinct effector cells to dendritic cells, rather than on instruction from pathogens--uses the effectiveness of particular effector cells at targeting and destroying a pathogen as a reliable, experience-based criterion to induce and maintain the appropriately polarized response.