A clonal culture system demonstrates that IL-4 induces a subpopulation of noncytolytic T cells with low CD8, perforin, and granzyme expression

Association Between Plasma Granzyme B Levels, Organ Failure, and 28-Day Mortality Prediction in Patients with Sepsis

Background/Objectives: Sepsis is basically an inflammatory disease that involves the host's immune response. Granzyme B, a cytotoxic protease, has garnered attention for its involvement in modulating immune responses. This study aimed to elucidate the clinical implications of granzyme B in critically ill patients with sepsis, focusing on plasma granzyme B levels as a potential prognostic marker. Methods: We conducted a retrospective analysis of sequentially collected blood samples from 57 sepsis patients admitted to the medical intensive care unit at Severance Hospital, a tertiary hospital in Seoul, South Korea. Clinical and laboratory data were comparatively analyzed between 28-day survivors and nonsurvivors. Results: The number of patients in the survivor and nonsurvivor groups was 32 (56.1%) and 25 (43.9%), respectively. Compared to survivors, nonsurvivors had higher APACHE II (23.5 vs. 34, p = 0.007) and SOFA (10 vs. 15, p = 0.001) scores, as well as increased levels of serum lactate (1.8 vs. 9.2 mmol/L, p < 0.001) and plasma granzyme B (28.2 vs. 71 pg/mL, p < 0.001). Granzyme B exhibited a robust area under the receiving operating characteristic (AUROC) for predicting 28-day mortality (AUROC = 0.794), comparable to lactate (0.804), SOFA (0.764), and APACHE II (0.709). The combined index of lactate and granzyme B demonstrated the highest AUROC (0.838) among all investigated predictors. Significant positive correlations were observed between log granzyme B and various inflammatory cytokines, including log IFN-γ (r = 0.780), IL-4 (r = 0.540), IL-10 (r = 0.534), and IL-6 (r = 0.520). Conclusions: Plasma granzyme B demonstrated fair short-term mortality prediction among patients admitted to the ICU, suggesting its potential utility for risk stratification and managing patients with sepsis.

Shape-Versatile Fixed Cellular Materials for Multiple Target Immunomodulation

Therapeutic cells are usually administered as living agents, despite the risks of undesired cell migration and acquisition of unpredictable phenotypes. Additionally, most cell-based therapies rely on the administration of single cells, often associated with rapid in vivo clearance. 3D cellular materials may be useful to prolong the effect of cellular therapies and offer the possibility of creating structural volumetric constructs. Here, the manufacturing of shape-versatile fixed cell-based materials with immunomodulatory properties is reported. Living cell aggregates with different shapes (spheres and centimeter-long fibers) are fixed using a method compatible with maintenance of structural integrity, robustness, and flexibility of 3D constructs. The biological properties of living cells can be modulated before fixation, rendering an in vitro anti-inflammatory effect toward human macrophages, in line with a decreased activation of the nuclear factor kappa B (NF-κB) pathway that preponderantly correlated with the surface area of the materials. These findings are further corroborated in vivo in mouse skin wounds. Contact with fixed materials also reduces the proliferation of activated primary T lymphocytes, while promoting regulatory populations. The fixation of cellular constructs is proposed as a versatile phenotypic stabilization method that can be easily implemented to prepare immunomodulatory materials with therapeutic potential.

Double-Negative T (DNT) Cells in Patients with Systemic Lupus Erythematosus

Double-negative T (DNT) cells are a rare and unconventional T-lymphocyte subpopulation lacking both CD4 and CD8 markers. Their immunopathological roles and clinical relevance have yet to be elucidated. Beyond autoimmune lymphoproliferative syndrome (ALPS), these cells may also play a role in rheumatic disorders, including systemic lupus erythematosus (SLE); indeed, these two diseases share several autoimmune manifestations (including nephritis). Moreover, one of the main experimental murine models used to investigate lupus, namely the MRL/lpr mouse, is characterized by an expansion of DNT cells, which can support the production of pathogenic autoantibodies and/or modulate the immune response in this context. However, lupus murine models are not completely consistent with their human SLE counterpart, of course. In this mini review, we summarize and analyze the most relevant clinical studies investigating the DNT cell population in SLE patients. Overall, based on the present literature review and analysis, DNT cell homeostasis seems to be altered in patients with SLE. Indeed, most of the available clinical studies (which include both adults and children) reported an increased DNT cell percentage in SLE patients, especially during the active phases, even though no clear correlation with disease activity and/or inflammatory parameters has been clearly established. Well-designed, standardized, and longitudinal clinical studies focused on DNT cell population are needed, in order to further elucidate the actual contribution of these cells in SLE pathogenesis and their interactions with other immune cells (also implicated and/or altered in SLE, such as basophils), and clarify whether their expansion and/or immunophenotypic aspects may have any immunopathological relevance (and, then, represent potential disease markers and, in perspective, even therapeutic targets) or are just an unspecific epiphenomenon of autoimmunity.

The mRNA expression and secretion of granzyme B are up-regulated via the histamine H2 receptor in human CD4+ T cells

INTRODUCTION

Granzyme B (GZMB), a serine protease with cytotoxic and immunomodulatory functions, shows elevated levels in blood plasma of patients with atopic dermatitis (AD). It has been observed that GZMB expression in CD4+ and CD8+ T cells is higher in lesional skin in AD than in healthy skin. Since histamine is present in high concentration in the skin of AD patients, we investigated the regulation of GZMB in human CD4+ T cells by histamine.

METHODS

Naïve CD4+ T cells polarized into Th2 cells, total CD4+ T cells treated with IL-4 for 72 h and CD4+ T cells isolated from healthy donors and AD patients were investigated. The cells were stimulated with histamine or with different histamine-receptor agonists. Gene expression was evaluated by RNA-Seq. GZMB mRNA expression was detected by quantitative real time PCR, whereas GZMB secretion was measured by ELISpot and ELISA. T cell degranulation was evaluated by flow cytometry using CD107a surface expression as a degranulation marker.

RESULTS

By RNA-Seq, we identified the up-regulation of various genes of the cytotoxic pathway, in particular of GZMB, by histamine in Th2-polarized CD4+ T cells. In Th2-polarized CD4+ T cells and in CD4+ T cells activated by IL-4 the mRNA expression of GZMB was significantly up-regulated by histamine and by histamine H2 receptor (H2R) agonists. The induction of GZMB secretion by histamine was significantly higher in CD4+ T cells from AD patients than in those from healthy donors. CD107a surface expression was up-regulated by trend in response to histamine in Th2-polarized CD4+ T cells.

CONCLUSION

Our findings may help to elucidate novel mechanisms of the H2R and to achieve a better understanding of the role of GZMB in the pathogenesis of AD.

Changing roles of CD3 + CD8 low T cells in combating HIV-1 infection

BACKGROUND

Cluster of differentiation 8 (CD8 T) cells play critical roles in eradicating human immunodeficiency virus (HIV)-1 infection, but little is known about the effects of T cells expressing CD8 at low levels (CD8 low ) or high levels (CD8 high ) on HIV-1 replication inhibition after HIV-1 invasion into individual.

METHODS

Nineteen patients who had been acutely infected with HIV-1 (AHI) and 20 patients with chronic infection (CHI) for ≥2 years were enrolled in this study to investigate the dynamics of the quantity, activation, and immune responses of CD3 + CD8 low T cells and their counterpart CD3 + CD8 high T cells at different stages of HIV-1 infection.

RESULTS

Compared with healthy donors, CD3 + CD8 low T cells expanded in HIV-1-infected individuals at different stages of infection. As HIV-1 infection progressed, CD3 + CD8 low T cells gradually decreased. Simultaneously, CD3 + CD8 high T cells was significantly reduced in the first month of AHI and then increased gradually as HIV-1 infection progressed. The classical activation of CD3 + CD8 low T cells was highest in the first month of AHI and then reduced as HIV-1 infection progressed and entered the chronic stage. Meanwhile, activated CD38 - HLA-DR + CD8 low T cells did not increase in the first month of AHI, and the number of these cells was inversely associated with viral load ( r = -0.664, P = 0.004) but positively associated with the CD4 T-cell count ( r = 0.586, P = 0.014). Increased programmed cell death protein 1 (PD-1) abundance on CD3 + CD8 low T cells was observed from the 1st month of AHI but did not continue to be enhanced, while a significant T cell immunoreceptor with immunoglobulin and immunoreceptor tyrosine-based inhibition motif (ITIM) domains (TIGIT) abundance increase was observed in the 12th month of infection. Furthermore, increased PD-1 and TIGIT abundance on CD3 + CD8 low T cells was associated with a low CD4 T-cell count (PD-1: r = -0.456, P = 0.043; TIGIT: r = -0.488, P = 0.029) in CHI. Nonetheless, the nonincrease in PD-1 expression on classically activated CD3 + CD8 low T cells was inversely associated with HIV-1 viremia in the first month of AHI ( r = -0.578, P = 0.015). Notably, in the first month of AHI, few CD3 + CD8 low T cells, but comparable amounts of CD3 + CD8 high T cells, responded to Gag peptides. Then, weaker HIV-1-specific T-cell responses were induced in CD3 + CD8 low T cells than CD3 + CD8 high T cells at the 3rd and 12th months of AHI and in CHI.

CONCLUSIONS

Our findings suggest that CD3 + CD8 low T cells play an anti-HIV role in the first month of infection due to their abundance but induce a weak HIV-1-specific immune response. Subsequently, CD3 + CD8 low T-cell number decreased gradually as infection persisted, and their anti-HIV functions were inferior to those of CD3 + CD8 high T cells.

The emerging roles of Hedgehog signaling in tumor immune microenvironment

The Hedgehog (Hh) signaling pathway is pervasively involved in human malignancies, making it an effective target for cancer treatment for decades. In addition to its direct role in regulating cancer cell attributes, recent work indicates that it has an immunoregulatory effect on tumor microenvironments. An integrated understanding of these actions of Hh signaling pathway in tumor cells and tumor microenvironments will pave the way for novel tumor treatments and further advances in anti-tumor immunotherapy. In this review, we discuss the most recent research about Hh signaling pathway transduction, with a particular emphasis on its role in modulating tumor immune/stroma cell phenotype and function, such as macrophage polarity, T cell response, and fibroblast activation, as well as their mutual interactions between tumor cells and nonneoplastic cells. We also summarize the recent advances in the development of Hh pathway inhibitors and nanoparticle formulation for Hh pathway modulation. We suggest that targeting Hh signaling effects on both tumor cells and tumor immune microenvironments could be more synergistic for cancer treatment.

Double Negative T Regulatory Cells: An Emerging Paradigm Shift in Reproductive Immune Tolerance?

Immune regulation of female reproductive function plays a crucial role in fertility, as alterations in the relationship between immune and reproductive processes result in autoimmune subfertility or infertility. The breakdown of immune tolerance leads to ovulation dysfunction, implantation failure, and pregnancy loss. In this regard, immune cells with regulatory activities are essential to restore self-tolerance. Apart from regulatory T cells, double negative T regulatory cells (DNTregs) characterized by TCRαβ+/γδ+CD3+CD4–CD8– (and negative for natural killer cell markers) are emerging as effector cells capable of mediating immune tolerance in the female reproductive system. DNTregs are present in the female reproductive tract of humans and murine models. However, their full potential as immune regulators is evolving, and studies so far indicate that DNTregs exhibit features that can also maintain tolerance in the female reproductive microenvironment. This review describes recent progress on the presence, role and mechanisms of DNTregs in the female reproductive system immune regulation and tolerance. In addition, we address how DNTregs can potentially provide a paradigm shift from the known roles of conventional regulatory T cells and immune tolerance by maintaining and restoring balance in the reproductive microenvironment of female fertility.

Interleukin-33 Reinvigorates Antiviral Function of Viral-Specific CD8+ T Cells in Chronic Hepatitis B Virus Infection

Restoration of exhausted hepatitis B virus (HBV)-specific CD8⁺ T cells is one of the important strategies for inhibition of viral replication. The role of interleukin (IL)-33 to recovery of CD8⁺ T cell activity is not fully elucidated. We investigated the effect of IL-33 on viral-specific CD8⁺ T cell responses in chronic hepatitis B (CHB) patients in vitro by both phenotypic and functional analysis. Plasma IL-33 was downregulated in CHB patients, while effective antiviral therapy rescued IL-33 expression. There was no significant difference of IL-33 receptor mRNA relative level in CD8⁺ T cells between CHB patients and controls. IL-33 induced the proliferation of HBV-specific CD8⁺ T cells, and reduced programmed death-1 expression on HBV-specific CD8⁺ T cells. IL-33 promoted the direct cytolytic activity of CD8⁺ T cells against HepG2.2.15 cells through boosting perforin and granzyme B production. Furthermore, IL-33 administration increased HBV-specific CD8⁺ T cell-mediated HBV replication and HBV antigen secretion mainly via enhancement of interferon-γ and tumor necrosis factor-α. IL-33 reinvigorated antiviral activity of HBV-specific CD8⁺ T cells, revealing that IL-33 might contribute to viral clearance in persistent HBV infection.

Multifunctional, TNF-α and IFN-γ-Secreting CD4 and CD8 T Cells and CD8High T Cells Are Associated With the Cure of Human Visceral Leishmaniasis

Visceral leishmaniasis (VL) is a chronic and often fatal disease caused by protozoans of the genus Leishmania that affects millions of people worldwide. Patients with symptomatic VL have an impaired anti-Leishmania-specific CD4⁺ T-cell response, which is reversed after clinical cure. In contrast, the quality of the CD4⁺ and CD8⁺ T-cell responses involved in resistance and/or cure of VL relies on the capability of these cells to activate polyfunctional and memory responses, which are associated with the simultaneous production of three cytokines: IFN-γ, IL-2, and TNF-α. Models for the development of CD4 and CD8 T-cell quality in memory and protection to leishmaniasis have been described previously. We aimed to assess the functionality of the T cells involved in the recovery of the immune suppression throughout the VL treatment. Therefore, we cultured peripheral blood mononuclear cells (PBMCs) from VL patients and healthy controls in vitro with soluble Leishmania antigen (SLA). Cell surface markers and intracellular cytokine production were determined on days 7, 14, 21, 30, 60, 90, and 180 after the beginning of chemotherapy. We observed that the frequencies of CD4⁺TNF-α⁺IFN-γ⁺ and the multifunctional CD4⁺IL-2⁺TNF-α⁺IFN-γ⁺, together with CD4⁺TNF-α⁺ and CD4⁺IFN-γ⁺ T cells, increased throughout and at the end of the treatment, respectively. In addition, enhanced frequencies of CD8⁺IL-2⁺TNF-α⁺IFN-γ⁺ and CD8⁺TNF-α⁺IFN-γ T cells were also relevant in the healing process. Noteworthy, the frequencies of the CD4⁺ and CD8 central-memory T cells, which produce IL-2, TNF-α, and IFN-γ and ensure the memory response against parasite reinfection, are significantly enhanced in cured patients. In addition, the subset of the non-functional CD8^Low population is predominant in VL untreated patients and decreases along the chemotherapy treatment. In contrast, a CD8^High subset increased towards the cure. Furthermore, the cure due to treatment with meglumine antimoniate or with liposomal amphotericin B was associated with the recovery of the T-cell immune responses. We described the evolution and participation of functional T cells during the treatment of patients with VL. Our results disclosed that the clinical improvement of patients is significantly associated with the participation of the CD4⁺ and CD8⁺ cytokine-secreting T cells.

STAT3 determines IL-4 signalling outcomes in naïve T cells

IL-4 production is associated with low-avidity, poorly cytotoxic T cell induction that contributes to viral immune evasion and the failure of T cell-based vaccines. Yet, the precise mechanisms that regulate IL-4 signalling in T cells remain elusive. Mounting evidence indicates that cells can dynamically alter their IL-4/IL-13 receptor signature to modulate downstream immune outcomes upon pathogen encounter. Here, we describe how naïve (CD62L⁺CD44^lo-mid) CD4 and CD8 T cells distinctly engage both STAT6 and STAT3 in response to IL-4. We further show that IL-4R⍺ expression is both time- and IL-4 concentration-dependent. Remarkably, our findings reveal that STAT3 inhibition can ablate IL-4R⍺ and affect transcriptional expression of other Stat and Jak family members. By extension, the loss of STAT3 lead to aberrant STAT6 phosphorylation, revealing an inter-regulatory relationship between the two transcription factors. Moreover, IL-4 stimulation down-regulated TGF-β1 and IFN-γR1 expression on naïve T cells, possibly signifying the broad regulatory implications of IL-4 in conditioning lineage commitment decisions during early infection. Surprisingly, naïve T cells were unresponsive to IL-13 stimulation, unlike dendritic cells. Collectively, these findings could be exploited to inform more efficacious vaccines, as well as design treatments against IL-4/IL-13-associated disease conditions.

Cytokine Syntheses by T-Cell Subsets From Chronic Myeloid Leukemia Patients: Relationship Between Pre-Treatment Levels and Response to Imatinib Therapy

Background

Although T-cell cytokine's role in the long-term control of chronic myeloid leukemia (CML) is well established, previous studies showed contradicting results regarding imatinib (IM) effect on the endogenous T-cell function by IM. The purpose of this study was to determine the relation between the endogenous T-cell function prior to therapy and the degree of response to IM therapy in CP CML. In addition, modulation of the endogenous T-cell function during IM therapy was studied.

Methods

We evaluated Th1 (gamma interferon (IFN-γ)), Th2 (interleukin (IL-4)) and tumor necrosis factor (TNF)-α cytokine synthesis by activated T-cell subsets in 20 patients with newly diagnosed CML in chronic phase (CP CML) using flow cytometry before and during IM therapy compared to patients with IM resistance (IM Res) and healthy donors.

Results

Patients with optimal response (CML OR) to IM demonstrated a lower pre-treatment Th1 cytokine compared to that of healthy donors, and a higher percentage of Th2 and TNF-α producing T cells compared to that of healthy donors, non-optimal responders (CML nOR) and those with IM Res. A shift from Th2 profile to Th1 profile and initial decline of TNF-α producing T cells was detected early during therapy in optimal responders which was coinciding with complete hematological remission with a significant increase in the percentages of CD4+ve/IFN-γ+ve cells (P = 0.01) and a significant drop of in CD8+ve/IL-4+ve T cells (P = 0.04).

Conclusion

We believe that pre-treatment levels of IL-4 and/or TNF-α may have a role in identifying CP CML patients who may respond to IM therapy; however, further investigation is needed.

CD8 down-regulation on cytotoxic T lymphocytes of patients with endometrioid endometrial carcinomas

Carcinogenesis is a multistep process in which cancer cells and tumor stroma cells play important roles. T lymphocytes are immune constituents of tumor stroma and play a crucial function in anti-tumor response. By immunohistochemistry and flow cytometry, we studied T cytotoxic (CTLs) and T helper lymphocyte distribution and percentage in the tumor microenvironment and peripheral blood from 35 patients with endometrioid endometrial carcinomas (EEC). We also studied 23 healthy donors' blood samples as a control group. Tumor and non-tumoral endometrium samples were obtained. Immunohistochemistry revealed a high number of CTLs and T helper lymphocytes in the tumor stroma of myoinvasive EECs. T lymphocytes were mostly located in the invasive front. By flow cytometry, the percentages of CTLs and T helper lymphocytes were significantly higher in the tumor compared with the non-neoplastic endometrium (P = .0492 and P = .002). The mean fluorescence intensity of CD8 staining was lower in the tumor compared to the non-neoplastic endometrium (P = .001). There was also reduction of the mean fluorescence intensity of CD8 staining on peripheral blood from patients with grade 3 EECs compare to the peripheral blood from healthy donors (P = .0093). No alterations in the expression of granzymes A and B were found in the CTLs from the EEC cases. Finally, in a proteome profiler cytokine array we found that the growth differentiation factor 15 (GDF15) increased in blood in parallel to the tumor grade. EECs are capable of down-regulating CD8 expression of CTLs. Most likely, this effect is mediated by a soluble molecule present in plasma and is not a result of anergy or exhaustion state.

Malaria - how this parasitic infection aids and abets EBV-associated Burkitt lymphomagenesis

Burkitt lymphoma (BL) is >90% EBV-associated when this pediatric cancer is diagnosed in regions heavily burden by endemic Plasmodium falciparum malaria and thus has been geographically classified as endemic BL. The incidence of endemic BL is 10-fold higher compared to BL diagnosed in non-malarious regions of the world. The other forms of BL have been classified as sporadic BL which contain EBV in ∼30% of cases and immunodeficiency BL which occurs in HIV-infected adults with ∼40% of tumors containing EBV. Within malaria endemic regions, epidemiologic studies replicating Denis Burkitt's seminal observation continue to show differences in endemic BL incidence linked to intensity of malaria transmission. However, the mechanisms by which malaria contributes to B cell tumorigenesis have not been resolved to the point of designing cancer prevention strategies. The focus of this review is to summarize our current knowledge regarding the influence of prolonged, chronic malaria exposure on defects in immunosurveillance that would otherwise control persistent EBV infections. And thus, set the stage for ensuing mechanisms by which malaria could instigate B cell activation and aberrant activation-induced cytidine deaminase expression initiating somatic hypermutation and thereby increasing the likelihood of an Ig/Myc translocation, the hallmark of all BL tumors. Malaria appears to play multiple, sequential and simultaneous roles in endemic BL etiology; the complexity of these interactions are being revealed by applying computational methods to human immunology. Remaining questions yet to be addressed and prevention strategies will also be discussed.

Blockade of programmed death-1/programmed death ligand pathway enhances the antitumor immunity of human invariant natural killer T cells

The role of invariant natural killer T (iNKT) cells in antitumor immunity has been studied extensively, and clinical trials in patients with advanced cancer have revealed a prolonged survival in some cases. In recent years, humanized blocking antibodies against co-stimulatory molecules such as PD-1 have been developed. The enhancement of T cell function is reported to improve antitumor immunity, leading to positive clinical effects. However, there are limited data on the role of PD-1/programmed death ligand (PDL) molecules in human iNKT cells. In this study, we investigated the interaction between PD-1 on iNKT cells and PDL on antigen-presenting cells (APCs) in the context of iNKT cell stimulation. The blockade of PDL1 at the time of stimulation resulted in increased release of helper T cell (Th) 1 cytokines from iNKT cells, leading to the activation of NK cells. The direct antitumor function of iNKT cells was also enhanced after stimulation with anti-PDL1 antibody-treated APCs. According to these results, we conclude that the co-administration of anti-PDL1 antibody and alpha-galactosylceramide (αGalCer)-pulsed APCs enhances iNKT cell-mediated antitumor immunity.

Quantitative assessment of the functional plasticity of memory CD8(+) T cells

While the functional plasticity of memory CD4(+) T cells has been studied extensively, less is known about this property in memory CD8(+) T cells. Here, we report the direct measurement of plasticity by paired daughter analysis of effector and memory OT-I CD8(+) T cells primed in vivo with ovalbumin. Naïve, effector, and memory OT-I cells were isolated and activated in single-cell culture; then, after the first division, their daughter cells were transferred to new cultures with and without IL-4; expression of IFN-γ and IL-4 mRNAs was measured 5 days later in the resultant subclones. Approximately 40% of clonogenic memory CD8(+) T cells were bipotential in this assay, giving rise to an IL-4(-) subclone in the absence of IL-4 and an IL-4(+) subclone in the presence of IL-4. The frequency of bipotential cells was lower among memory cells than naïve cells but markedly higher than among 8-day effectors. Separation based on high or low expression of CD62L, CD122, CD127, or Ly6C did not identify a phenotypic marker of the bipotential cells. Functional plasticity in memory CD8(+) T-cell populations can therefore reflect modulation at the level of a single memory cell and its progeny.

Severe feline sporotrichosis associated with an increased population of CD8low cells and a decrease in CD4⁺ cells

Sporotrichosis is a subcutaneous mycosis with worldwide distribution, especially in tropical and subtropical areas. Zoonotic transmission is described with cats being the main animal species involved. The occurrence of severe feline sporotrichosis with high fungal levels demonstrates the susceptibility of cats to this disease and the importance of studying its pathogenesis. This study describes the leukocytes profile in blood of cats with sporotrichosis by flow cytometry and its correlation with histopathology and fungal load. The cats with sporotrichosis were separated into groups L1, L2, and L3 (lesions at one, two, and three or more noncontiguous skin locations, respectively) and were classified as good, fair, or poor general conditions. The highest percentage of CD4+ cells was associated to L1 (P = .04) and to good general condition (P = .03). The percentage of CD8+ cells was greater in L2 and L3 (P = .01). CD8(low) expression occurred in 20 animals with sporotrichosis, mainly in L3 (P = .01) and was not observed in healthy controls. This expression was related to macrophage granulomas (P = .01) and predominated in cases with high fungal load. Altogether, the results indicated that control over feline sporotrichosis, with maintenance of a good general condition, fixed lesions, well-organized response and lower fungal load, is associated with increased CD4+ cells percentages. In contrast, a poor general condition, disseminated lesions and high fungal load were related to increased CD8+ cell percentages and increased expression of CD8(low). As conclusion these results point to an important role of the CD4:CD8 balance in determining the clinical outcome in feline sporotrichosis.

Targeting IL4/IL4R for the treatment of epithelial cancer metastasis

While progress has been made in treating primary epithelial tumors, metastatic tumors remain largely incurable and still account for 85-90 % of all cancer-related deaths. Interleukin-4 (IL4), a Th2 cytokine, and the IL4/IL4 receptor (IL4R) interaction have well defined roles in the immune system. Yet, IL4 receptors are over-expressed by many epithelial cancers and could be a promising target for metastatic tumor therapy. The IL4/IL4R signaling axis is a strong promoter of pro-metastatic phenotypes in epithelial cancer cells including enhanced migration, invasion, survival, and proliferation. The promotion of breast cancer growth specifically is also supported in part by IL4-induced glutamine metabolism, and we have shown that IL4 is also capable of inducing glucose metabolism in breast cancer cells. Importantly, there are several types of FDA approved medications for use in asthma patients that inhibit the IL4/IL4R signaling axis. However, these approved medications inhibit both the type I IL4 receptor found on immune cells, and the type II IL4 receptor that is predominantly expressed by some non-hematopoietic cells including epithelial cancer cells. This article reviews existing therapies targeting IL4, IL4R, or IL4/IL4R signaling, and recent findings guiding the creation of novel therapies that specifically inhibit the type II IL4R, while taking into consideration effects on immune cells within the tumor microenvironment. Some of these therapies are currently in clinical trials for cancer patients, and may be exploitable for the treatment of metastatic disease.

Role of Chinese herbal medicinal ingredients in secretion of cytokines by PCV2-induced endothelial cells

While T-lymphocytes are the major cell type responsible for host responses to a virus (including induction of inflammatory responses to aid in ultimate removal of virus), other cells, including macrophages, epithelial and dendritic cells also have key roles. Endothelial cells also play important roles in physiologic/pathologic processes, like inflammation, during viral infections. As endothelial cells can be activated to release various endogenous compounds, including some cytokines, ex vivo measures of cytokine formation by the cells can be used to indirectly assess any potential endothelial dysfunction in situ. The research presented here sought to investigate potential immunolomodulatory effects of five saponins on endothelial cells: Saikosaponins A (SSA) and D (SSD), Panax Notoginseng Saponin (PNS) and Notoginsenoside R1 (SR1) and Anemoside B4 (AB4). For this, cells (porcine iliac artery endothelial line) were challenged with a virus isolate PCV2-AH for 24 h and then treated with the test saponin (at 1, 5 or 10 μg/ml) for an additional 24 h at 37 °C. The culture supernatants were then collected and analyzed for interleukin (IL)-2, -4 and -10, as well as interferon (IFN)-γ by ELISA. The results revealed that PNS and SR1 inhibited the production of IL-4; PNS, SR1 and AB4 inhibited the secretion of IL-10; SSA, SSD and PNS up-regulated IL-2 expression; SSA and SSD increased the level of IFNγ. All these changes were significant. Taken together, the data suggested these saponins might potentially have a capacity to regulate immune responses in vivo via changes in production of these select cytokines by infected endothelial cells. Nevertheless, the impact of these agents on other key cell types involved in anti-viral responses, including T-lymphocytes, remains to be determined.

CD8(low)CD28(-) T Cells: A Human CD8 T-Suppressor Subpopulation With Alloantigen Specificity Induced by Soluble HLA-A2 Dimer In Vitro

CD8(+) suppressor T cells have been demonstrated to provide protection of allografts from rejection. We previously reported that soluble peptide/HLA-A2 dimer shows peptide-specific inhibitory effects on alloresponse in a coculture of peptide-pulsed T2 cells with HLA-A2 negative lymphocytes in vitro. Here we found a subset of CD8(low)CD28(-) T cells that was induced in the dimer-treated coculture. Importantly, this population showed hyporesponsiveness to the alloantigen restimulation as well as alloantigen-specific suppression on alloreactive T cells in a cell-cell contact-dependent fashion. The suppressive mechanisms of CD8(low)CD28(-) T cells involved an elevated expression of membrane-bound TGF-β1, but not Foxp3, CTLA-4, or IL-10. Furthermore, an overrepresention of CD8(low)CD28(-) T cells was observed in the patients after allogeneic platelet transfusion and positively correlated with the elevated concentrations of plasma HLA class I antigens. Our findings demonstrated that soluble HLA-A2 dimer could efficiently induce the tolerant CD8(low)CD28(-) T cells with alloantigen-specific suppression on alloreactive T cells. This study might provide a new strategy for preparation of donor-specific suppressor T cells and represent an attractive alternative for induction of allograft tolerance.

Epigenetic plasticity of Cd8a locus during CD8(+) T-cell development and effector differentiation and reprogramming

Modulation of CD8 coreceptor levels can profoundly affect T-cell sensitivity to antigen. Here we show that the heritable downregulation of CD8 during type 2 polarization of murine CD8⁺ effector T cells in vitro and in vivo is associated with CpG methylation of several regions of the Cd8a locus. These epigenetic modifications are maintained long-term in vivo following adoptive transfer. Even after extended type 2 polarization, however, some CD8^low effector cells respond to interferon-γ by re-expressing CD8 and a type 1 cytokine profile in association with partial Cd8a demethylation. Cd8a methylation signatures in naive, polarized and repolarized cells are distinct from those observed during the initiation, maintenance and silencing of CD8 expression by developing T cells in the thymus. This persistent capacity for epigenetic reprogramming of coreceptor levels on effector CD8⁺ T cells enables the heritable tuning of antigen sensitivity in parallel with changes in type 1/type 2 cytokine balance.

CD8 expression levels on peripheral CD8+ T cells are regulated during development and effector differentiation. Here, the authors show that methylation patterns at the Cd8a locus, whose product is essential for surface CD8 expression, can change during T-cell development, activation, cytokine polarization and reprogramming.

IL-4: an important cytokine in determining the fate of T cells

The pleiotropic effect of cytokines has been well documented, but the effects triggered by unique cytokines in different T cell types are still under investigation. The most relevant findings on the influence of interleukin-4 (IL-4) on T cell activation, differentiation, proliferation, and survival of different T cell types are discussed in this review. The main aim of our study was to correlate the observed effect with the corresponding molecular mechanism induced on IL-4/IL-4R interaction, in an effort to understand how the same extracellular stimuli can trigger a wide spectrum of signaling pathways leading to different responses in each T cell type.

Memory cytolytic T-lymphocytes: induction, regulation and implications for vaccine design

The design of vaccines that protect against intracellular infections or cancer remains a challenge. In many cases, immunity depends on the development of antigen-specific memory CD8+ T-cells that can express cytokines and kill antigen-bearing cells when they encounter the pathogen or tumor. Here, the authors review current understanding of the signals and cells that lead to memory CD8+ T-cell differentiation, the relationship between the primary CD8+ T-cell response and the memory response and the regulation of memory CD8+ T-cell survival and function. The implications of this new knowledge for vaccine design are discussed, and recent progress in the development of lipidated peptide vaccines as a promising approach for vaccination against intracellular infections and cancer is reviewed.

CD8low T-cell subpopulation is increased in patients with chronic hepatitis B virus infection

Recent studies suggest that CD8(+) T cells with down-regulated CD8 expression (CD3(+)CD8(low) T cells) represented as a distinct phenotype of CD8(+) T cells are increased and linked to disease severity in some chronically persistent infection, such as chronic HIV and parasite infection. However, the role of CD3(+)CD8(low) T cells in the context of chronic HBV infection is poorly understood. In this study, peripheral blood samples of 47 chronic hepatitis B patients and 19 healthy controls were collected and tested for the frequency and phenotype of CD8(low) T cells. The circulating CD8(low) T cells were significantly more frequent in the patients compared to those in healthy controls, and the CD8(low) T cells in the patients expressed less IFN-γ and more mTGF-β1 than those in the controls, suggesting their type-2 polarized and suppressive properties. Meanwhile, the concentrations of plasma soluble HLA class I molecules were found elevated in the patients, and positively associated with the frequencies of CD8(low) T cells. Furthermore, the CD8(low) T-cell frequency in the HLA-A2-positive patients (n=21) was found negatively correlated with the T-cell responsiveness against the HBc₁₈₋₂₇ peptide, the latter was impaired as revealed by IFN-γ Elispot assay. Our findings suggested that a better understanding of the involvement of CD8(low) T cells in chronically persistent HBV infection would add to our knowledge of the impaired T-cell response in the patients.

Interleukin-4-induced loss of CD8 expression and cytolytic function in effector CD8 T cells persists long term in vivo

Activation of naive CD8(+) T cells in the presence of interleukin-4 modulates their CD8 co-receptor expression and functional differentiation, resulting in the generation of CD8(low) cells that produce type 2 cytokines and display poor cytolytic and anti-tumour activity. Although this CD8(low) phenotype becomes stable after about a week and can persist with further stimulation in vitro, it is not known whether it can be maintained long term in vivo. Here we report that CD8(low) cells derived from oval-bumin(257-264) -specific T-cell receptor-transgenic CD8(+) T cells activated in the presence of interleukin-4 could be detected in the spleen for at least 4 months after adoptive transfer into normal mice. A significant proportion of the long-term surviving cells retained their CD8(low) phenotype in vivo and after clonal re-activation in vitro. Although long-term surviving CD8(low) cells lacked detectable cytolytic activity or perforin expression, they showed some anti-tumour function in vivo. The persistence of functional cells with a CD8(low) phenotype in vivo raises the possibility that such cells can contribute to effector or regulatory responses to tumours or pathogens.

Systemic reduction of interleukin-4 or interleukin-10 fails to reduce the frequency or severity of experimental cytomegalovirus retinitis in mice with retrovirus-induced immunosuppression

Interleukin-4 (IL-4) and interleukin-10 (IL-10) are key cytokines whose increased production during systemic HIV infection has been associated with decreased cellular immunity during AIDS. We examined whether HIV-induced stimulation of IL-4 or IL-10 production leads to increased susceptibility to AIDS-related human cytomegalovirus retinitis. It was confirmed that there were increased amounts of IL-4 and IL-10 mRNA levels in mice with MAIDS of 10 weeks duration when most susceptible to MCMV retinitis. Surprisingly, however, MCMV-infected eyes of IL-4 -/- and IL-10 -/- mice with MAIDS of 8 weeks duration exhibited retinitis and infectious virus equivalent to that observed in MCMV-infected eyes of wild-type mice with MAIDS. We conclude that neither IL-4 nor IL-10 alone play a role in increased susceptibility to MAIDS-related MCMV retinitis, but may work collectively with other retrovirus-induced immunosuppressive factors to allow for retinal disease.

T-cell receptor gene transfer exclusively to human CD8(+) cells enhances tumor cell killing

Transfer of tumor-specific T-cell receptor (TCR) genes into patient T cells is a promising strategy in cancer immunotherapy. We describe here a novel vector (CD8-LV) derived from lentivirus, which delivers genes exclusively and specifically to CD8(+) cells. CD8-LV mediated stable in vitro and in vivo reporter gene transfer as well as efficient transfer of genes encoding TCRs recognizing the melanoma antigen tyrosinase. Strikingly, T cells genetically modified with CD8-LV killed melanoma cells reproducibly more efficiently than CD8(+) cells transduced with a conventional lentiviral vector. Neither TCR expression levels, nor the rate of activation-induced death of transduced cells differed between both vector types. Instead, CD8-LV transduced cells showed increased granzyme B and perforin levels as well as an up-regulation of CD8 surface expression in a small subpopulation of cells. Thus, a possible mechanism for CD8-LV enhanced tumor cell killing may be based on activation of the effector functions of CD8(+) T cells by the vector particle displaying OKT8-derived CD8-scFv and an increase of the surface density of CD8, which functions as coreceptor for tumor-cell recognition. CD8-LV represents a powerful novel vector for TCR gene therapy and other applications in immunotherapy and basic research requiring CD8(+) cell-specific gene delivery.

Use of praziquantel as an adjuvant enhances protection and Tc-17 responses to killed H5N1 virus vaccine in mice

Background

H5N1 is a highly pathogenic influenza A virus, which can cause severe illness or even death in humans. Although the widely used killed vaccines are able to provide some protection against infection via neutralizing antibodies, cytotoxic T-lymphocyte responses that are thought to eradicate viral infections are lacking.

Methodology/Principal Findings

Aiming to promote cytotoxic responses against H5N1 infection, we extended our previous finding that praziquantel (PZQ) can act as an adjuvant to induce IL-17-producing CD8⁺ T cells (Tc17). We found that a single immunization of 57BL/6 mice with killed viral vaccine plus PZQ induced antigen-specific Tc17 cells, some of which also secreted IFN-γ. The induced Tc17 had cytolytic activities. Induction of these cells was impaired in CD8 knockout (KO) or IFN-γ KO mice, and was even lower in IL-17 KO mice. Importantly, the inoculation of killed vaccine with PZQ significantly reduced virus loads in the lung tissues and prolonged survival. Protection against H5N1 virus infection was obtained by adoptively transferring PZQ-primed wild type CD8⁺ T cells and this was more effective than transfer of activated IFN-γ KO or IL-17 KO CD8⁺ T cells.

Conclusions/Significance

Our results demonstrated that adding PZQ to killed H5N1 vaccine could promote broad Tc17-mediated cytotoxic T lymphocyte activity, resulting in improved control of highly pathogenic avian influenza virus infection.

The multiple roles of the CD8 coreceptor in T cell biology: opportunities for the selective modulation of self-reactive cytotoxic T cells

Short peptide fragments generated by intracellular protein cleavage are presented on the surface of most nucleated cells bound to highly polymorphic MHCI molecules. These pMHCI complexes constitute an interface that allows the immune system to identify and eradicate anomalous cells, such as those that harbor infectious agents, through the activation of CTLs. Molecular recognition of pMHCI complexes is mediated primarily by clonally distributed TCRs expressed on the surface of CTLs. The coreceptor CD8 contributes to this antigen-recognition process by binding to a largely invariant region of the MHCI molecule and by promoting intracellular signaling, the effects of which serve to enhance TCR stimuli triggered by cognate ligands. Recent investigations have shed light on the role of CD8 in the activation of MHCI-restricted, antigen-experienced T cells and in the processes of T cell selection and lineage commitment in the thymus. Here, we review these data and discuss their implications for the development of potential therapeutic strategies that selectively target pathogenic CTL responses erroneously directed against self-derived antigens.

Praziquantel facilitates IFN-γ-producing CD8+ T cells (Tc1) and IL-17-producing CD8+ T cells (Tc17) responses to DNA vaccination in mice

Background

CD8⁺ cytotoxic T lymphocytes (CTLs) are crucial for eliminating hepatitis B virus (HBV) infected cells. DNA vaccination, a novel therapeutic strategy for chronic virus infection, has been shown to induce CTL responses. However, accumulated data have shown that CTLs could not be effectively induced by HBV DNA vaccination.

Methodology/Principal Findings

Here, we report that praziquantel (PZQ), an anti-schistoma drug, could act as an adjuvant to overcome the lack of potent CTL responses by HBV DNA vaccination in mice. PZQ in combination with HBV DNA vaccination augmented the induction of CD8⁺ T cell-dependent and HBV-specific delayed hypersensitivity responses (DTH) in C57BL/6 mice. Furthermore, the induced CD8⁺ T cells consisted of both Tc1 and Tc17 subtypes. By using IFN-γ knockout (KO) mice and IL-17 KO mice, both cytokines were found to be involved in the DTH. The relevance of these findings to HBV immunization was established in HBsAg transgenic mice, in which PZQ also augmented the induction of HBV-specific Tc1 and Tc17 cells and resulted in reduction of HBsAg positive hepatocytes. Adoptive transfer experiments further showed that PZQ-primed CD8⁺ T cells from wild type mice, but not the counterpart from IFN-γ KO or IL-17 KO mice, resulted in elimination of HBsAg positive hepatocytes.

Conclusions/Significance

Our results suggest that PZQ is an effective adjuvant to facilitate Tc1 and Tc17 responses to HBV DNA vaccination, inducing broad CD8⁺ T cell-based immunotherapy that breaks tolerance to HBsAg.

Alternative activation of tumor-associated macrophages by IL-4: priming for protumoral functions

Although macrophages were originally recognized as major immune effector cells, it is now appreciated that they also play many important roles in the maintenance of tissue homeostasis, and are involved in a variety of pathological conditions including cancer. Several studies have demonstrated the contributions of tumor-associated macrophages (TAMs) to tumor initiation, progression, and metastasis. However, the detailed mechanisms underlying how TAMs differ molecularly from their normal counterparts and how the conversion to TAMs occurs have only just begun to be understood. TAMs have been proposed to exhibit phenotypes of 'alternatively activated' macrophages, though there has been limited evidence directly linking the phenotypes of TAMs to the alternative activation of macrophages. This review will focus on IL-4, the prototypic cytokine that induces the alternative activation of macrophages, and review current knowledge regarding the contributions of IL-4 to the phenotypes of TAMs and its effects on tumorigenesis.

IFN-gamma inhibits IL-4-induced type 2 cytokine expression by CD8 T cells in vivo and modulates the anti-tumor response

Activation of naive CD8 T cells in vitro in the presence of IL-4 induces type 2 cytokine expression, loss of CD8 expression, and reduced cytolytic potential. This represents a major shift from the canonical phenotype of effector CD8 T cells. It has not been established, however, whether IL-4 can induce comprehensive type 2 cytokine expression by CD8 T cells in vivo, nor whether the effects of IL-4 on type 2 cytokine production by CD8 T cells can be inhibited by IFN-gamma. Furthermore, disparate results have been reported regarding the anti-tumor ability of type 2 polarized effector CD8 T cells, and the effects of IFN-gamma in this respect remain unknown. To address these questions, wild-type or IFN-gamma-deficient OVA-specific CD8(+) T cells were activated in RAG-2(-/-) gamma c(-/-) recipients with control or IL-4-expressing OVA(+) tumor cells, and then transferred to secondary recipients for tumor challenge. Tumor-derived IL-4 induced the expression of type 2 cytokines and the transcription factor GATA-3 by responding CD8 T cells while reducing their CD8 coreceptor expression and ability to eliminate a secondary tumor challenge. Each of these effects of IL-4 was exaggerated in IFN-gamma-deficient, compared with wild-type, CD8 T cells. The results demonstrate that endogenous IFN-gamma counteracts the induction of type 2 cytokines and the downregulation of both CD8 coreceptor levels and the anti-tumor response in CD8 T cells exposed to IL-4 during activation in vivo. These findings may explain the anomalies in the reported functional phenotype of type 2 polarized CD8 T cells.

Pancreatic lipase-related protein 2 (PLRP2) induction by IL-4 in cytotoxic T lymphocytes (CTLs) and reevaluation of the negative effects of its gene ablation on cytotoxicity

Pancreatic lipase-related protein 2 (PLRP2) is induced by IL-4 in vitro in cytotoxic T lymphocyte (CTL) clones and CTLs from immunized wild-type (WT) PLRP2(+/+) are more cytotoxic than PLRP2(-/-) CTLs, suggesting to previous investigators that the lipase PLRP2 might support CTL functions. Here, we further evaluate PLRP2 in CTLs. We found that PLRP2 was optimally induced in splenocytes by 3.5 x 10(-8) M IL-4 by day 6 after activation and was restricted to CD8(+) T cells. PLRP2 mRNA was detected inconsistently (and at low levels) after activation in the presence of IL-2. Cytotoxicity in 4 h (51)Cr assays of WT CTLs was approximately 3-fold the activity of PLRP2(-/-) CTLs cultured with IL-4 and, with IL-2, was unexpectedly approximately 2 fold the activity of PLRP2(-/-) CTLs. Thus, PLRP2 gene ablation affected short-term (perforin-dependent) cytotoxicity, even under the IL-2 conditions. Other variables failed to account for the reduced cytotoxicity. Granzyme B levels, activation markers, and CD8(+) T cell frequencies were similar for WT vs. PLRP2(-/-) CTLs (with either cytokine). Addition of rPLRP2 to IL-4 induced PLRP2(-/-) CTLs (or to cytotoxic granule extracts) failed to increase lysis, suggesting that the missing mediator is more than released PLRP2. Cytotoxicity of WT and PLRP2(-/-) CTLs was similar in 2-day tumor survival assays with IL-4, which can be mediated by perforin-independent mechanisms. We conclude that extracellular PLRP2 lipase is unable to directly augment the cytotoxicity that was lost by PLRP2 ablation and that after reevaluation, the question of what is PLRP2's role in CD8 T cells is still unanswered.

Immunohistochemical analysis of granzyme B in non-perforated appendicitis--short communication

The aim of the present study was to determine the expression ofgranzyme B in non-perforated appendicitis. Appendix biopsies were obtained from the patients with clinically diagnosed as acute appendicitis and subjects admitted for elective abdominal surgery. All biopsies from the patients were non-perforated and histologically divided into acute and non-acute appendicitis. Granzyme B expression was assessed immunohistochemically. The results showed that granzyme B expression in both acute and non-acute appendicitis was significantly lower than that in the control appendix tissues (P < 0.05). The expression of this cytotoxic protein in acute and non-acute appendicitis was comparable (P > 0.05). Therefore, the results of the present study suggest that reduced expression of granzyme B in non-perforated appendicitis may reflect low cytotoxic activities which may prevent tissue damage.

IL-2 and antigen dose differentially regulate perforin- and FasL-mediated cytolytic activity in antigen specific CD4+ T cells

CD4 T cell effectors can promote survival against lethal influenza virus via perforin mediated cytolytic mechanisms; however, our understanding of how naïve CD4 cells differentiate into class II restricted killers remains obscure. To address this, TCR Tg CD4 cells were activated in vitro and examined for their ability to lyse target cells. We found that cytokine polarized CD4 T cell effectors displayed cytolytic activity with the hierarchy Th0>Th1>Th2. Further, IL-4 inhibited the generation of cytotoxic CD4 cells. LPS stimulated B cells and bone marrow derived dendritic cells (BMDC) both induced potent cytolytic activity; however, IL-6, TGF-beta, IL-10, IL-12 or TNF-alpha were not required for inducing cytolytic activity in CD4 effectors. Antigen dose had a marked effect on cytotoxicity: low concentrations of peptide induced more potent cytolytic activity than relatively high concentrations. At low peptide concentration, exogenous IL-2 was necessary to drive granzyme B (GrB) expression and perforin mediated lysis. Thus, low antigen dose and early activation signals via IL-2 direct the CD4 T cell response toward effectors with perforin mediated cytolytic potential. These data have implications for the design of vaccines that may induce cytolytic CD4 cells in vivo and improve cell-mediated immunity to viral and bacterial infections.

Hydrolysis of tumor cell lipids after CTL-mediated death

Contributions of lipases to CTL function have been debated, including if T cell lipases damage target cells. Expression of the lipase pancreatic lipase-related protein 2 (PLRP2) was previously found in IL-4 cultured lymphocyte cell lines but absent from IL-2 cultured lymphocytes. Here, we evaluated IL-2 and IL-4 induced CTLs for hydrolysis of target cell lipids and killing. Using anti-CD3 redirected lysis of [(3)H]-oleic acid-labeled P815 tumor cells, we detected the release of the radioactive fatty acid (FA). When PLRP2(+/+) and PLRP2(-/-) CTLs were compared, there was more killing by the PLRP2(+/+) CTLs. However, [(3)H]-oleic acid release was similar per dead P815, suggesting that lipid hydrolysis was produced by the dead P815s rather than by PLRP2. The FA release and death were completely dependent on perforin and also occurred when P815s were killed by perforin-containing T cell granule extracts that lacked lipase activity. Death by the cytotoxic granules extracts was unaffected by the addition of lipases. A lipase inhibitor, tetrahydrolipstatin, blocked FA release without affecting CTL-mediated cytotoxicity. Also, CTL-mediated death caused as much FA release as death by disruption of cells by freeze-thawing. The released oleic acid may be sufficient to promote secondary apoptotic responses after CTL-induced trauma.

Prospects for an influenza vaccine that induces cross-protective cytotoxic T lymphocytes

Our approach to vaccination against influenza is unique. For no other pathogen do we construct and produce a new vaccine every year in the face of uncertainty about the strains that will be circulating when it is used. The huge global cooperative effort that underpins this process reflects our awareness of the need to control this major pathogen. Moreover, the threat of devastation by a pandemic due to a newly emerging viral subtype has triggered an intense effort to improve and accelerate the production of vaccines for use if a pandemic arises. However, type A influenza viruses responsible for seasonal epidemics and those with the potential to cause a pandemic share amino acid sequences that form the targets of cytotoxic T lymphocytes (CTL). CTL activated by currently circulating viruses, therefore, offer a possible means to limit the impact of infection with future variant seasonal strains and even new subtypes. This review examines how cross-protective CTL can be exploited to improve influenza vaccination and issues that need to be considered when attempting to induce this type of immunity. We discuss the role of CTL responses in viral control and review the current knowledge relating to specificity and longevity of memory CD8(+) T cells, how vaccine antigen can be loaded into antigen-presenting cells to prime these responses and factors influencing the class of response induced. Application of these principles to the next generation of influenza vaccines should lead to much greater control of infection.

Interleukin-4 suppresses the cytotoxic potential of in vitro generated, adaptive regulatory CD4 T cells by down-regulation of granzyme B

Regulatory CD4+ T cells (Tregs) control immune responses using secretion of anti-inflammatory cytokines and/or cytotoxic mechanisms and play a central role in the outcomes of several immune pathologies. Previous studies suggest an impaired function of Tregs in allergy, especially during allergen seasons, but the underlying mechanism is not known. Therefore, we analysed the impact of the T helper type 2 cytokine interleukin (IL)-4 on in vitro generated adaptive Tregs (aTregs), which have been reported to use the granzyme B (GrB)/perforin pathway to kill autologous immune cells. aTregs were generated by co-ligation of CD3 and CD46 on CD4+ T lymphocytes and granzyme expression was analysed using flow cytometry. To quantify GrB and perforin expression as well as IL-10 secretion in response to IL-4, specific enzyme-linked immunosorbent assays were performed in cell lysates and/or culture supernatants. Using a flow cytometry-based cytotoxicity assay the impact of IL-4 on the cytotoxic potential of aTregs was investigated. While IL-4 did not affect IL-10 secretion and perforin expression in aTregs, a significant suppression of GrB synthesis was detected in the presence of IL-4. In addition, IL-4-mediated suppression of GrB led to impaired cytotoxicity of aTregs against K562 target cells. In conclusion, our data suggest that IL-4 might play a role in impaired aTreg function in allergy.

Interferon-gamma and interleukin-4 reciprocally regulate CD8 expression in CD8+ T cells

The CD8 co-receptor can modulate CD8(+) T cell function through its contributions to T cell receptor (TCR) binding and signaling. Here we show that IFN-gamma and IL-4 exert opposing effects on the expression of CD8alpha mRNA and surface CD8 protein during CD8(+) T cell activation. IL-4 caused down-regulation of surface CD8 on ovalbumin (OVA)(257-264)-specific TCR-transgenic OT-I CD8(+) T cells activated with OVA(257-264)-coated antigen presenting cells or polyclonal stimuli, and on wild type CD8(+) T cells activated with polyclonal stimuli. This effect was enhanced in each case when the cells lacked a functional IFN-gamma or IFN-gamma R gene. When WT or IFN-gamma-deficient OT-I CD8(+) T cells were analyzed 9 days after co-injection with control or IL-4-expressing OVA(+) tumor cells into RAG-2(-/-)gamma c(-/-) mice, CD8 levels were highest on WT donor cells from mice that received the control tumor and lowest on IFN-gamma-deficient donor cells from mice that received the IL-4-expressing tumor. The latter CD8(low) cells displayed markedly impaired binding of OVA(257-264)/MHC tetramers and peptide/MHC-dependent degranulation. The data reveal an unexpected role for IFN-gamma in tuning the CD8 co-receptor during primary CD8(+) T cell activation both in vitro and in vivo.

Coligation of the hepatitis C virus receptor CD81 with CD28 primes naive T lymphocytes to acquire type 2 effector function

Costimuli provide supplementary signals required by naive T cells to become fully activated upon Ag encounter. Tetraspanins are a large family of transmembrane proteins that can costimulate T cells when engaged in vitro. In this study, we describe for the first time that coligation of the tetraspanins CD81, CD82, or CD9 with the costimulatory molecule CD28 in vitro leads to proliferation of naive T cells. When activated through this pathway, both CD4+ and CD8+ naive T cells differentiate into type 2 effector cells, which produce IL-4, IL-5, IL-13, and IL-10, together with IL-2 and TNF-alpha, but little to no IFN-gamma. These effector cells descend from precursors that display early and strong production of IL-4, STAT6 phosphorylation, and up-regulation of the transcription factor GATA-3, suggesting a direct skewing toward Th2 differentiation without a Th0 intermediate. The hepatitis C virus envelope protein E2 is the only ligand known for CD81. Therefore, we propose that this new type of Ag-independent T cell activation may occur in hepatitis C virus-infected individuals, contributing to liver inflammation, impaired type 1 immune responses, and recurrent flares of type 2 immunity associated with chronic infection.

Branched and linear lipopeptide vaccines have different effects on primary CD4+ and CD8+ T-cell activation but induce similar tumor-protective memory CD8+ T-cell responses

We compared murine T-cell responses to synthetic lipopeptide vaccines in which the TLR2 ligand Pam(2)Cys was attached to co-linear CD4+ and CD8+ T-cell epitopes of ovalbumin (OVA) in a linear or branched configuration. Mice received OVA-specific transgenic CD8+ and CD4+ T-cells followed by one injection of vaccine. Although the branched lipopeptide was more potent in activating OVA-specific CD4+ and CD8+ T-cells in the primary response, both vaccines induced cytolytic T lymphocytes (CTL) that expressed perforin, granzyme A-C, and IFN-gamma mRNAs and conferred long-term protection of most mice against challenge with OVA-expressing tumor cells. OVA epitope display was reduced in tumors that developed in some mice, suggesting CD8+ T-cell dependent selection.

Allergen immunotherapy in intermittent allergic rhinitis reduces the intracellular expression of IL-4 by CD8+ T cells

BACKGROUND

T helper subset dysregulation is evident in allergic disorders. The role of T cytotoxic subsets is less understood. We investigated whether allergen immunotherapy in intermittent allergic rhinitis influences the intracellular expression of IL-4 and IFN-gamma by CD3+CD8(-) and CD3+CD8+ cells.

METHODS

Nineteen adult patients with intermittent allergic rhinitis were evaluated before the pollen season, and then after one preseasonal course of subcutaneous allergen immunotherapy. Twelve healthy nonatopic patients matched for age and sex served as controls. Intracellular expression of IFN-gamma and IL-4 by CD3+CD8(-) (Th1 and Th2, respectively) and CD3+CD8+ (Tc1 and Tc2, respectively) was estimated by flow cytometry in peripheral blood cells after stimulation with PMA and ionomycin.

RESULTS

Before immunotherapy the percentages of Th1, Th2, Tc1 and Tc2 did not significantly differ between the patients and the controls. After immunotherapy the percentage of Tc2 was lower in the rhinitic patients than in the controls (0.38% vs. 0.45%, p=0.04). The percentage of Tc2 cells decreased significantly after immunotherapy in the intermittent allergic rhinitis group (0.64% vs. 0.38%, p=0.02) with tendency to decrease in ratios of Tc2/Tc1 (p=0.059) and with no changes in ratios of Th2/Th1. The percentages of Th1, Th2 and Tc1 were comparable before and after immunotherapy within the rhinitic patient group.

CONCLUSIONS

The preseasonal allergen subcutaneous immunotherapy applied to intermittent allergic rhinitis patients suppressed the percentage of IL-4 producing CD3+CD8+ cells. Decreased number of CD3+CD8+IL-4+ cells may participate in the regulatory mechanisms of immunotherapy.

Detuning CD8 T cells: down-regulation of CD8 expression, tetramer binding, and response during CTL activation

CD8 is critical for T cell recognition of peptide/class I major histocompatability complex ligands, yet is down-regulated during activation of CD8 T cells. We report that loss of CD8 expression early during in vivo responses to vaccinia virus or Listeria monocytogenes (LM) correlates with decreased T cell staining with specific class I/peptide tetramers and reduced CD8 T cell sensitivity for antigen. Loss of CD8 cell surface expression occurs despite sustained mRNA expression, and CD8 levels return to normal levels during differentiation of memory cells, indicating a transient effect. We determined that during response to LM, CD8 down-regulation is regulated by T cell reactivity to type I interferon (IFN-I) because CD8 loss was averted on IFN-I receptor-deficient T cells. IFN-I alone was not sufficient to drive CD8 down-regulation, however, as antigen was also required for CD8 loss. These results suggest that CD8 effector T cell differentiation involves a transient down-regulation of antigen sensitivity (CTL "detuning"), via reduced CD8 expression, a feature that may focus the effector response on target cells expressing high levels of antigen (e.g., infected cells), while limiting collateral damage to bystander cells.

Interleukin-4 impairs granzyme-mediated cytotoxicity of Simian virus 40 large tumor antigen-specific CTL in BALB/c mice

In this report we analyzed the impact of interleukin-4 (IL-4) on tumor-associated simian virus 40 (SV40) large T-antigen (TAg)-specific CD8+ cytotoxic T cells during rejection of syngeneic SV40 transformed mKSA tumor cells in BALB/c mice. Strikingly, challenge of naïve mice with low doses of mKSA tumor cells revealed a CD8+ T cell-dependent prolonged survival time of naïve IL-4-/- mice. In mice immunized with SV40 TAg we observed in IL-4-/- mice, or in wild type mice treated with neutralizing anti-IL-4 monoclonal antibody, a strongly enhanced TAg-specific cytotoxicity of tumor associated CD8+ T cells. The enhanced cytotoxicity in IL-4-/- mice was accompanied by a significant increase in the fraction of CD8+ tumor associated T-cells expressing the cytotoxic effector molecules granzyme A and B and in granzyme B-specific enzymatic activity. The data suggest that endogenous IL-4 can suppress the generation of CD8+ CTL expressing cytotoxic effector molecules especially when the antigen induces only a very weak CTL response.

The duplicitous effects of interleukin 4 on tumour immunity: how can the same cytokine improve or impair control of tumour growth?

Successful tumour immunity relies on innate and adaptive immune responses, with cytokines like interleukin 4 (IL-4) known to influence tumour clearance in both positive and negative ways. Here, we summarise some of the murine tumour models used over the past two decades to assess the impact of IL-4 on tumour immunity, with emphasis on the effects of IL-4 on the tumour-induced CD8 T-cell response. These data are compared with our own recent studies showing that IL-4 impairs CD8+ T-cell-mediated immunity against the mastocytoma cell line P815 expressing the immunogenic HLA-CW3 gene; moreover, we hypothesise that quantitative and qualitative differences in the HLA-CW3-induced CD8+ T-cell response impair control of tumour growth and aid the development of secondary tumours. We conclude that the duplicitous effects of IL-4 on tumour immunity depend on the type of effector cell (adaptive/innate) mediating tumour clearance and whether tumour growth depends on stromal infrastructure. Thus, the search for factors that improve or weaken the effectiveness of tumour-specific T cells has to be continued to improve modern approaches of immunotherapy against cancer.

Mucosal HIV-1 Pox Virus Prime-Boost Immunization Induces High-Avidity CD8+ T Cells with Regime-Dependent Cytokine/Granzyme B Profiles

The quality of virus-specific CD8(+) CTL immune responses generated by mucosal and systemic poxvirus prime-boost vaccines were evaluated in terms of T cell avidity and single-cell analysis of effector gene expression. Intranasal (I.N.) immunization regimes generated higher avidity CTL responses specific for HIV K(d)Gag(197-205) (amino acid sequence AMQMLKETI; H-2K(d) binding) compared with i.m. immunization regime. Single-cell RT-PCR of K(d)Gag(197-205)-specific mucosal and systemic CTL revealed that the cytokine and granzyme B expression profiles were dependent on both the route and time after immunization. The I.N./i.m.-immunized group elicited elevated number of CTL-expressing granzyme B mRNA from the genitomucosal sites compared with the i.m./i.m. regime. Interestingly, CTL generated after both I.N. or i.m. immunization demonstrated expression of Th2 cytokine IL-4 mRNA that was constitutively expressed over time, although lower numbers were observed after I.N./I.N. immunization. Results suggest that after immunization, Ag-specific CTL expression of IL-4 may be an inherent property of the highly evolved poxvirus vectors. Current observations indicate that the quality of CTL immunity generated after immunization can be influenced by the inherent property of vaccine vectors and route of vaccine delivery. A greater understanding of these factors will be crucial for the development of effective vaccines in the future.

IL-4 induces a wide-spectrum intracellular signaling cascade in CD8+T cells

IL-4 has distinct effects on the differentiation and functional properties of CD8+ T cells. In vivo studies have shown that it is critical for the development of protective memory responses against tumors and infections by Leishmania and Plasmodium parasites. The intracellular signaling events mediated by IL-4/IL-4 receptor (IL-4R) interactions on CD4+ T cells have been studied extensively; however, the nature of IL-4-induced signaling on CD8+ T cells has not been characterized. Using naïve, activated, as well as differentiated CD8+ T cells, we show that IL-4 has a strong in vivo and in vitro antiapoptotic effect on activated and resting CD8+ T cells. We demonstrate that IL-4 induces the phosphorylation of the IL-4R, which is followed by the activation of at least two distinct intracellular signaling cascades: the Jak1/STAT6 and the insulin receptor substrate/PI-3K/protein kinase B pathways. We also found that IL-4 induces the Jak3-mediated phosphorylation and nuclear migration of STAT1, STAT3, and STAT5 in naïve, activated, as well as differentiated, IFN-gamma-producing CD8+ T cells. The induction of this broad signaling activity in CD8+ T cells coincides with a transcriptional activity of suppressors of cytokine signaling genes, which are decreased significantly in comparison with CD4+ T cells. To our knowledge, this report constitutes the first comprehensive analysis of the signaling events that shape CD8+ T cell responses to IL-4.

Decrease of cytotoxic T cells in allergic asthma correlates with total serum immunglobulin E

BACKGROUND

Allergic asthma has been linked to an increase in T-helper type 2-like cytokines and T cells, but there is growing evidence for a role of lymphocyte-mediated cytotoxic mechanisms in the pathogenesis of asthma. Therefore, we investigated the cytotoxic potential of different lymphocyte subpopulations in patients with allergic asthma.

METHODS

Granzyme A, B, K, and perforin expression in peripheral blood lymphocytes was analyzed using flow cytometry. Soluble granzymes were measured in serum using specific enzyme-linked immunosorbent assays.

RESULTS

Asthmatics had significantly decreased percentages of granzyme and perforin-positive CD4 T cells compared with non-atopic controls. In patients with asthma, the granzyme B and perforin-positive subset of CD8(+) T cells and natural killer T cells, which represent more differentiated cell populations, were significantly reduced, while this was not observed in the less differentiated granzyme K(+) subsets. In addition, the serum concentrations of granzyme B were significantly reduced in patients with asthma, while granzyme K concentrations were not different. Interestingly, there was a negative correlation between granzyme A, B and perforin expression in T cell subsets as well as serum granzyme B concentrations and total serum immunglobulin E. In CD3-negative natural killer cells, no differences in granzyme or perforin expression between patients with asthma and controls were detected.

CONCLUSION

In allergic asthma, cytotoxic T lymphocyte subsets of a more differentiated phenotype are significantly decreased and this is correlated to serum immunglobulin E levels.

Double-negative T regulatory cells can develop outside the thymus and do not mature from CD8+ T cell precursors

Recent studies have demonstrated that activated peripheral alphabeta TCR+ CD3+ CD4- CD8- NK1.1- (double-negative, DN) regulatory T cells (Tregs) from both mice and humans are able to down-regulate immune responses in vitro and in vivo. However, the origin and developmental requirements of functional DN Tregs remain unclear. In this study, we investigated the requirement for CD8 expression as well as the presence of a thymus for the development of functional DN Tregs. We demonstrate that DN Tregs exist in CD8-deficient mice and that stimulation of CD8+ T cells in vivo with TCR-specific Ag does not convert CD8+ T cells into DN Tregs. In addition, we found that DN T cells are present in the spleens and lymph nodes of thymectomized mice that are irradiated and reconstituted with T cell-depleted bone marrow cells. Interestingly, DN Tregs that develop in thymectomized mice can suppress syngeneic CD8+ T cells more effectively than those that develop in sham-thymectomized mice. Taken together, our data suggest that DN Tregs are not derived from CD8+ T cell precursors and that functional DN Tregs may preferentially develop outside of the thymus. These data suggest that DN Tregs may represent a developmentally and functionally unique cell population.