Possible mechanism for the alpha subunit of the interleukin-2 receptor (CD25) to influence interleukin-2 receptor signal transduction

Tanshinone I inhibits the functions of T lymphocytes and exerts therapeutic effects on delayed-type hypersensitivity reaction via blocking STATs signaling pathways

Delayed-type hypersensitivity (DTH) reactions are a kind of chronic inflammatory diseases initiated by antigens and antigen-specific T cells. Currently, the therapy of DTH reactions is limited by the poor curative effects and serious adverse reactions of existing agents. In this study, we investigated the regulatory effects of tanshinone Ⅰ, a natural compound isolated from Salvia miltiorrhiza, on the functions of multiple immune cells and its therapeutic effects on DNFB-induced DTH reaction, and then explored its immunosuppressive mechanisms. The results showed that tanshinone Ⅰ at 5-20 μM moderately inhibited the activation of macrophages and dendritic cells, but did not weaken the activation of neutrophils. Tanshinone Ⅰ at 1-4 μM intensively suppressed the activation, proliferation, and differentiation of CD4+ and CD8+ T cells, and slightly affected the functions of B cells. Tanshinone Ⅰ administration markedly alleviated the edema, inflammatory response, and the infiltrations of CD4+ T cells, CD8+ T cells, and CD11b+ cells in ear tissues of mice which were induced DTH reactions by DNFB. Transcriptome analysis revealed that tanshinone Ⅰ strongly inhibited CD4+ T cells to express genes involving in cell proliferation, metabolism, activation, and differentiation. Furthermore, immunoblotting analysis showed that tanshinone Ⅰ selectively inhibited the phosphorylation of STAT3 and STAT5 in CD4+ T cells stimulated by anti-CD3e and anti-CD28 antibodies or IL-2. Collectively, tanshinone Ⅰ can strongly inhibit the functions of T lymphocytes, exert therapeutic effects on DTH reaction by blocking STATs signaling pathways, and has potential to be developed into therapeutic drug for DTH reactions.

Type 1 diabetes and inborn errors of immunity: Complete strangers or 2 sides of the same coin?

Type 1 diabetes (T1D) is a polygenic disease and does not follow a mendelian pattern. Inborn errors of immunity (IEIs), on the other hand, are caused by damaging germline variants, suggesting that T1D and IEIs have nothing in common. Some IEIs, resulting from mutations in genes regulating regulatory T-cell homeostasis, are associated with elevated incidence of T1D. The genetic spectrum of IEIs is gradually being unraveled; consequently, molecular pathways underlying human monogenic autoimmunity are being identified. There is an appreciable overlap between some of these pathways and the genetic variants that determine T1D susceptibility, suggesting that after all, IEI and T1D are 2 sides of the same coin. The study of monogenic IEIs with a variable incidence of T1D has the potential to provide crucial insights into the mechanisms leading to T1D. These insights contribute to the definition of T1D endotypes and explain disease heterogeneity. In this review, we discuss the interconnected pathogenic pathways of autoimmunity, β-cell function, and primary immunodeficiency. We also examine the role of environmental factors in disease penetrance as well as the circumstantial evidence of IEI drugs in preventing and curing T1D in individuals with IEIs, suggesting the repositioning of these drugs also for T1D therapy.

Microglia depletion prevents lactation by inhibition of prolactin secretion

Microglial cells were eliminated from the brain with sustained 3-4 weeks long inhibition of colony stimulating factor 1 receptor by Pexidartinib 3397 (PLX3397). The prepartum treated mice mothers did not feed their pups after parturition. The pups of mothers treated orally only in the postpartum period starting immediately after parturition showed reduced body weight by 15.5 ± 0.22 postnatal days as the treatment progressed without the mothers showing altered caring behaviors. The apparent weight gain of foster pups during a suckling bout was reduced in mother mice fed by PLX3397-containing diet and also in rat dams following sustained intracerebroventricular infusion of PLX3397 in a separate experiment suggesting that lactation was affected by the reduced number of microglia. Prolactin secretion and signaling were markedly reduced in PLX3397-treated mothers. The results suggest that microglial cells are required for prolactin secretion and lactation whereas maternal motivation may not be directly affected by microglia.

Intracellular K+ and water content in human blood lymphocytes during transition from quiescence to proliferation

Many evidence shows that K⁺ ions are required for cell proliferation, however, changes in intracellular K⁺ concentration during transition of cells from quiescence to cycling are insufficiently studied. Here, we show using flame emission assay that a long-term increase in cell K⁺ content per g cell protein is a mandatory factor for transition of quiescent human peripheral blood lymphocytes (PBL) to proliferation induced by phytohemagglutinin, phorbol ester with ionomycin, and anti-CD3 antibodies with interleukin-2 (IL-2). The long-term increase in K⁺ content is associated with IL-2-dependent stage of PBL activation and accompanies the growth of small lymphocytes and their transformation into blasts. Inhibition of PBL proliferation with drugs specific for different steps of G0/G1/S transit prevented both blast-transformation and an increase in K⁺ content per cell protein. Determination of the water content in cells by measuring the density of cells in the Percoll gradient showed that, unlike the K⁺ content, the concentration of K⁺ in cell water remains unchanged, since water and K⁺ change in parallel. Correlation of proliferation with high cell K⁺ and water content has been confirmed by the data obtained in comparative study of PBL and permanently cycling Jurkat cells. Our data suggest that K⁺ is important for successful proliferation as the main intracellular ion that participates in regulation of cell water content during cell transition from quiescence to proliferation. We concluded that high K⁺ content in cells and the associated high water content is a characteristic feature of proliferating cells.

Evaluating STAT5 Phosphorylation as a Mean to Assess T Cell Proliferation

Here we present a simple and sensitive flow cytometric-based assay to assess T cell proliferation. Given the critical role STAT5A phosphorylation in T cell proliferation, we decided to evaluate phosphorylation of STAT5A as an indicator of T cell proliferation. We determined pSTAT5A in T cell treated with either CD3/CD28 or PHA. After stimulation, T cells from adult healthy donors displayed a strong long-lasting phosphorylation of STAT5A, reaching a peak value after 24 h. The median fluorescence intensity (MFI) of pSTAT5A increased from 112 ± 17 to 512 ± 278 (CD3/CD28) (24 h) and to 413 ± 123 (PHA) (24 h), the IL-2 receptor-α (CD25) expression was greatly enhanced and after 72 h T cell proliferation amounted to 52.3 ± 10.3% (CD3/CD28) and to 48.4 ± 9.7% (PHA). Treatment with specific JAK3 and STAT5 inhibitors resulted in a complete blockage of phosphorylation of STAT5A, CD25 expression, and suppression of T cell proliferation. Compared with currently available methods, STAT5A phosphorylation is well-suited to predict T cell proliferation. Moreover, the method presented here is not very time consuming (several hours) and delivers functional information from which conclusions about T cell proliferation can be drawn.

The effects of interleukin-2 on immune response regulation

The immune system has many adaptive and dynamic components that are regulated to ensure appropriate, precise and rapid response to a foreign pathogen. A delayed or inadequate immune response can lead to prolonged disease, while an excessive or under-regulated response can lead to autoimmunity. The cytokine, interleukin-2 (IL-2) and its receptor IL-2R play an important role in maintaining this balance.The IL-2 receptor transduces pSTAT5 signal through both the intermediate and high affinity receptors, which differ from each other by the presence of CD25 chain in IL-2 receptor. We present experimental data on the kinetics of pSTAT5 signalling through both of the receptors and develop a model that captures this kinetics. We then use this model to parameterize key aspects of two additional models in which we propose and study two different mechanisms by which IL-2 receptor can transduce distinct signals leading to either an activated or a non-activated cell state. We speculate that this initial state differentiation, perhaps enhanced by downstream feedbacks, may eventually lead to differential cell fates.Our result shows that non-linear dynamical models can suggest resolution of a puzzling array of seemingly contradictory experimental results on IL-2 effect on proliferation and differentiation of T-cells.

DOCK8 regulates fitness and function of regulatory T cells through modulation of IL-2 signaling

Foxp3+ Tregs possess potent immunosuppressive activity, which is critical for maintaining immune homeostasis and self-tolerance. Defects in Treg development or function result in inadvertent immune activation and autoimmunity. Despite recent advances in Treg biology, we still do not completely understand the molecular and cellular mechanisms governing the development and suppressive function of these cells. Here, we have demonstrated an essential role of the dedicator of cytokinesis 8 (DOCK8), guanine nucleotide exchange factors required for cytoskeleton rearrangement, cell migration, and immune cell survival in controlling Treg fitness and their function. Treg-specific DOCK8 deletion led to spontaneous multiorgan inflammation in mice due to uncontrolled T cell activation and production of proinflammatory cytokines. In addition, we show that DOCK8-deficient Tregs are defective in competitive fitness and in vivo suppressive function. Furthermore, DOCK8 controls IL-2 signaling, crucial for maintenance and competitive fitness of Tregs, via a STAT5-dependent manner. Our study provides potentially novel insights into the essential function of DOCK8 in Tregs and immune regulation, and it explains the autoimmune manifestations associated with DOCK8 deficiency.

Oncostatin M Suppresses Activation of IL-17/Th17 via SOCS3 Regulation in CD4+ T Cells

Oncostatin M (OSM) is a pleiotropic cytokine and a member of the IL-6 family. It has both proinflammatory and anti-inflammatory functions and is involved in the activation of STAT3 and STAT5. Rheumatoid arthritis is an autoimmune disease that causes chronic and excessive inflammation. Rheumatoid arthritis can lead to induction of Th17 cells, which express IL-17. The aim of this study was to measure the effects of OSM on the proliferation of regulatory T cells and Th17 cells from mice. IL-2 immune complex suppressed the development of collagen-induced arthritis in mice and altered the regulatory T/Th17 cell balance by increasing OSM expression. OSM mitigated the proliferation of Th17 cells and decreased the expression of IL-17 and IL-21. It promoted the activation of suppressor of cytokine signaling 3 (SOCS3), STAT3, and STAT5. Inhibition of SOCS3, STAT3, and STAT5 lessened the OSM-induced reduction in proliferation of Th17 cells. These observations suggest that OSM can inhibit Th17 differentiation by reciprocally controlling SOCS3, STAT3, and STAT5.

Time-Dependent Regulation of IL-2R α-Chain (CD25) Expression by TCR Signal Strength and IL-2-Induced STAT5 Signaling in Activated Human Blood T Lymphocytes

The expression of the IL-2R α-chain (IL-2Rα) is regulated at the transcriptional level via TCR- and IL-2R-signaling. The question is how to precede in time the activation signals to induce the IL-2Rα expression in native primary T cells. By comparing the effects of selective drugs on the dynamics of CD25 expression during the mitogen stimulation of human peripheral blood lymphocytes, we identified distinct Src- and JAK-dependent stages of IL-2Rα upregulation. PP2, a selective inhibitor of TCR-associated Src kinase, prevents CD25 expression at initial stages of T cell activation, prior to the cell growth. This early IL-2Rα upregulation underlies the T cell competence and the IL-2 responsiveness. We found that the activated with “weak” mitogen, the population of blood lymphocytes has some pool of competent CD25+ cells bearing a high affinity IL-2R. A distinct pattern of IL-2R signaling in resting and competent T lymphocytes has been shown. Based on the inhibitory effect of WHI-P131, a selective drug of JAK3 kinase activity, we concluded that in quiescent primary T lymphocytes, the constitutive STAT3 and the IL-2-induced prolonged STAT5 activity (assayed by tyrosine phosphorylation) is mostly JAK3-independent. In competent T cells, in the presence of IL-2 JAK3/STAT5 pathway is switched to maintain the higher and sustained IL-2Rα expression as well as cell growth and proliferation. We believe that understanding the temporal coordination of antigen- and cytokine-evoked signals in primary T cells may be useful for improving immunotherapeutic strategies.

Defective CD8 Signaling Pathways Delay Rejection in Older Recipients

CD8+ T cells play a cardinal feature in response to alloantigens and are able to generate effector/memory T cells independently from CD4+ T cells. To investigate the impact of aging on CD8 T cells, we used a fully mismatched mouse skin transplant model. Our findings showed a prolonged allograft survival in older recipients associated with a significant increase of CD4+ and CD8+ CD44high CD62Llow effector/memory T cells and a reduced systemic IFNγ production. When reconstituting young CBA Rag-1 mice that lack mature T and B cells with old CD8+ T cells expressing clonal anti-H2K T cell receptor (TCR) alloreactive for MHC I, graft survival was significantly prolonged and comparable to those receiving young CD8+ T cells. Moreover, our data showed that reduced systemic IFNγ levels observed in old recipients had been linked to a compromised expression of the IL-2R β subunit (CD122) by old CD8+ T cells. In addition, we observed an impaired IFNγ production on IL-2 receptor activation. At the same time, gene profiling analysis of old CD8 T cells demonstrated reduced chemokine ligand-3 and CD40L expression that resulted in compromised CD8+ T cell/dendritic cell communication, leading to impaired migratory and phagocytic activity of CD11c cells.Collectively, our study demonstrated that aging delays allograft rejection. CD8 T cells play a critical role in this process linked to a compromised production of IFNγ, in addition to a defective IL-2 receptor signaling machinery and a defective communication between CD8 T cells and dendritic cells.

Soluble cytokine receptors (sIL-2Rα, sIL-2Rβ) induce subunit-specific behavioral responses and accumulate in the cerebral cortex and basal forebrain

Soluble cytokine receptors are normal constituents of body fluids that regulate peripheral cytokine and lymphoid activity. Levels of soluble IL-2 receptors (sIL-2R) are elevated in psychiatric disorders linked with autoimmune processes, including ones in which repetitive stereotypic behaviors and motor disturbances are present. However, there is no evidence that sIL-2Rs (or any peripheral soluble receptor) induce such behavioral changes, or that they localize in relevant brain regions. Here, we determined in male Balb/c mice the effects of single peripheral injections of sIL-2Rα or sIL-2Rβ (0-2 µg/male Balb/c mouse; s.c.) on novelty-induced ambulatory activity and stereotypic motor behaviors. We discovered that sIL-2Rα increased the incidence of in-place stereotypic motor behaviors, including head up head bobbing, rearing/sniffing, turning, and grooming behavior. A wider spectrum of behavioral changes was evident in sIL-2Rβ-treated mice, including increases in vertical and horizontal ambulatory activity and stereotypic motor movements. To our knowledge, this is the first demonstration that soluble receptors induce such behavioral disturbances. In contrast, soluble IL-1 Type-1 receptors (0-4 µg, s.c.) didn't appreciably affect these behaviors. We further demonstrated that sIL-2Rα and sIL-2Rβ induced marked increases in c-Fos in caudate-putamen, nucleus accumbens and prefrontal cortex. Anatomical specificity was supported by the presence of increased activity in lateral caudate in sIL-2Rα treated mice, while sIL-2Rβ treated mice induced greater c-Fos activity in prepyriform cortex. Moreover, injected sIL-2Rs were widely distributed in regions that showed increased c-Fos expression. Thus, sIL-2Rα and sIL-2Rβ induce marked subunit- and soluble cytokine receptor-specific behavioral disturbances, which included increases in the expression of ambulatory activity and stereotypic motor behaviors, while inducing increased neuronal activity localized to cortex and striatum. These findings suggest that sIL-2Rs act as novel immune-to- brain messengers and raise the possibility that they contribute to the disease process in psychiatric disorders in which marked increases in these receptors have been reported.

Blood fluke exploitation of non-cognate CD4+ T cell help to facilitate parasite development

Schistosoma blood flukes, which infect over 200 million people globally, co-opt CD4⁺ T cell-dependent mechanisms to facilitate parasite development and egg excretion. The latter requires Th2 responses, while the mechanism underpinning the former has remained obscure. Using mice that are either defective in T cell receptor (TCR) signaling or that lack TCRs that can respond to schistosomes, we show that naïve CD4⁺ T cells facilitate schistosome development in the absence of T cell receptor signaling. Concurrently, the presence of naïve CD4⁺ T cells correlates with both steady-state changes in the expression of genes that are critical for the development of monocytes and macrophages and with significant changes in the composition of peripheral mononuclear phagocyte populations. Finally, we show that direct stimulation of the mononuclear phagocyte system restores blood fluke development in the absence of CD4⁺ T cells. Thus we conclude that schistosomes co-opt innate immune signals to facilitate their development and that the role of CD4⁺ T cells in this process may be limited to the provision of non-cognate help for mononuclear phagocyte function. Our findings have significance for understanding interactions between schistosomiasis and other co-infections, such as bacterial infections and human immunodeficiency virus infection, which potently stimulate innate responses or interfere with T cell help, respectively. An understanding of immunological factors that either promote or inhibit schistosome development may be valuable in guiding the development of efficacious new therapies and vaccines for schistosomiasis.

Schistosomes, or blood flukes, cause a debilitating illness in millions of people worldwide, which manifests when inflammation develops in response to parasite eggs that become trapped in the liver and other organs. Paradoxically, schistosomes require signals from the host's immune system in order to develop fully into egg-producing adults. Previously, we showed that CD4⁺ T cells facilitate schistosome development. Here, we show that the mere presence of CD4⁺ T cells is sufficient for schistosome development to proceed. There is no requirement for these cells to respond to the parasite, or to exhibit any typical “effector” response. Two pieces of data suggest this effect on parasite development is mediated by antigen-presenting cells of the innate immune system such as monocytes and macrophages, which interact with CD4⁺ T cells by expressing MHC class II molecules. First, the presence of naïve CD4⁺ T cells correlates with baseline changes in the development of monocyte/macrophage populations. Second, direct stimulation of the monocyte-macrophage system restores parasite development, bypassing the requirement for CD4⁺ T cells in schistosome development. Understanding the mechanisms that promote or inhibit blood fluke infection may facilitate the development of new treatments and vaccines for schistosomiasis.

T cell growth control using hapten-specific antibody/interleukin-2 receptor chimera

IL-2 is a cytokine that is essential for the expansion and survival of activated T cells. Although adoptive transfer of tumor-specific T cells with IL-2 is one of strategies for cancer immunotherapy, it is essential to replace IL-2 that exerts severe side effects in vivo. To solve this problem, we propose to use an antibody/IL-2R chimera, which can transduce a growth signal in response to a cognate antigen. We constructed two chimeras, in which ScFv of anti-fluorescein antibody was tethered to extracellular D2 domain of erythropoietin receptor and transmembrane/cytoplasmic domains of IL-2Rbeta or gamma chain. When the chimeras were co-expressed in IL-3-dependent pro-B cell line Ba/F3 and IL-2-dependent T cell line CTLL-2, gene-modified cells were selectively expanded in the absence of IL-3 and IL-2, respectively, by adding fluorescein-conjugated BSA (BSA-FL) as a cognate antigen. Growth assay revealed that the cells with the chimeras transduced a growth signal in a BSA-FL dose-dependent manner. Furthermore, STAT3, STAT5, ERK1/2 and Akt, which are hallmarks for IL-2R signaling, were all activated by the chimeras in CTLL-2 transfectant. We also demonstrated that the chimeras were functional in murine primary T cells. These results demonstrate that the antibody/IL-2R chimeras could substantially mimic the wild-type IL-2R and could specifically expand gene-modified T cells in the presence of the cognate antigen.

The influence of IL-2 family cytokines on activation and function of naturally occurring regulatory T cells

IL-2 is essential for CD4+CD25+forkhead box P3+ (FoxP3+) naturally occurring regulatory T cell (Treg) homeostasis and activation. Binding of IL-2 to its receptor leads to phosphorylation of STAT5, and binding of phosphorylated STAT5 to the foxp3 promoter increases foxp3 transcription, resulting in elevated levels of FoxP3 protein in Tregs. Transcriptional regulation by the elevated levels of FoxP3 is thought to be essential for the strong suppressor function seen in activated Tregs. IL-2 belongs to a family cytokines, which all depend on the common gamma-receptor chain (gammac). Given the well-documented effects of IL-2 on Treg function, the effect of other IL-2 family cytokines (IL-7, -15, and -21) on Tregs was examined. We observed that IL-7 and IL-15 induce STAT5 phosphorylation and up-regulation of FoxP3 in Tregs. STAT5 activation correlated with enhanced viability. However, only in the presence of IL-2 did Tregs acquire potent suppressor function. This finding is surprising, as IL-15 as well as IL-2 use the same IL-2R betac and gammac for signaling. In contrast, IL-21 activated STAT3 but did not activate STAT5 and had no effect on Treg viability, activation, or function. We therefore conclude that phosphorylation of STAT5, mediated through the IL-2Rgamma, promotes Treg survival in a resting and activated state. However, activation of STAT5 alone in conjunction with TCR signaling is not sufficient for the induction of potent suppressor function in Tregs, as IL-7 and IL-15 are not capable of inducing potent Treg suppressor function.

IL-2 triggers specific signaling pathways in human NKT cells leading to the production of pro- and anti-inflammatory cytokines

NKT cells belong to a conserved T lymphocyte subgroup that has been implicated in the regulation of various immune responses, including responses to viruses, bacteria, and parasites. They express a semi-invariant TCR that recognizes glycolipids presented by the nonpolymorphic MHC class I-like molecule CD1d, and upon activation, they produce various pro- and anti-inflammatory cytokines. Recent studies have shed light on the nature of glycolipids and the environmental signals that may influence the production of cytokines by NKT cells and thus, modulate the immune response. To better understand the regulation mechanisms of NKT cells, we explored their behavior following activation by IL-2 and investigated the signaling pathways and biological responses triggered. We demonstrated that IL-2 activates not only STAT3 and -5 and the PI-3K and ERK-2 pathways as in all IL-2 responder cells but also STAT4 as in NK cells and the p38 MAPK pathway as in alphabeta T cells. We also showed that STAT6 is activated by IL-2 in NKT cells. Moreover, IL-2 induces the production of IFN-gamma and IL-4. The ability of IL-2 to induce pro- and anti-inflammatory cytokine production, in addition to proliferation, could open new therapeutic approaches for use in combination with molecules that activate NKT cells through TCR activation.

The common gamma chain cytokines interleukin (IL)-2 and IL-7 indirectly modulate blood fluke development via effects on CD4+ T cells

The human pathogen Schistosoma mansoni exhibits a highly evolved and intricate relationship with its host, evading immune destruction while co-opting CD4(+) T cell-driven mechanisms to facilitate parasite development and egg excretion. Because the common gamma ( gamma (c)) chain cytokine interleukin (IL)-7 is also implicated in modulating schistosome development, we investigated whether this effect is mediated indirectly through the essential role that IL-7 plays in CD4(+) T cell growth and survival. We demonstrate that attenuated schistosome development in the absence of IL-7 results from dysregulated T cell homeostasis and not from disruption of direct interactions between schistosomes and IL-7. We also identify an indirect role that another gamma (c) chain cytokine plays in schistosome development, demonstrating that IL-2 expression by CD4(+) T cells is essential for normal parasite development. Thus, cytokines critical for CD4(+) T cell survival and function can mediate indirect but potent effects on developing schistosomes and underscore the importance of CD4(+) T cells in facilitating schistosome development.

Efficacy and safety of basiliximab in kidney transplantation

The efficacy and safety of basiliximab, in combination with different maintenance regimens, are extensively addressed in the available literature. Basiliximab reduces the incidence of acute rejection, allows a safe reduction of steroid dosage, and is associated with economic savings, although there is substantially no proof that basiliximab prolongs either patient or graft survival. Initial basiliximab administration entails a low-risk and is associated with fewer adverse events than T cell depleting agents. However, life-threatening reactions were reported following re-exposure to basiliximab in recipients who lost graft function early after transplantation and, therefore, discontinued all immunosuppressive agents.

Impaired up-regulation of CD25 on CD4+ T cells in IFN-gamma knockout mice is associated with progression of myocarditis to heart failure

Inflammation has been recognized increasingly as a critical pathologic component of a number of heart diseases. A mouse model of autoimmune myocarditis was developed to study the role of immune mediators in the development of cardiac dysfunction. We have found previously that IFN-gamma deficiency promotes inflammation in murine myocarditis. It has been unclear, however, how IFN-gamma deficiency in myocarditis affects cardiac function and what underlying immune mechanisms are responsible for these effects. In this work, we show that IFN-gamma knockout (KO) mice have more pronounced systolic and diastolic dysfunction and greater frequency of progression to dilated cardiomyopathy and heart failure compared with WT mice. Cardiac dysfunction in the KO mice is associated with the expansion of activated (CD44(high)) CD3+ T cells due to reduced apoptosis of CD4+, but not CD8+, T cells. CD4+ T cells in the KO mice show impaired up-regulation of CD25 upon activation, resulting in the expansion of CD4+CD44+CD25- T cells and their infiltration into the heart. CD4+CD25- T cells are less apoptosis-prone compared with the CD25+ population, and their infiltration into the heart is associated with greater severity of myocarditis. We conclude that IFN-gamma deficiency in autoimmune myocarditis is associated with preferential expansion of CD4+CD44+CD25- T cells resulting in increased cardiac inflammation. An exaggerated inflammatory response in IFN-gamma KO mice causes cardiac dysfunction, leading to dilated cardiomyopathy and heart failure.

Effect of Maitake (Grifola frondosa) D-Fraction on the activation of NK cells in cancer patients

Maitake D-Fraction, extracted from maitake mushroom, has been reported to exert its antitumor effect in tumor-bearing mice by enhancing the immune system through activation of macrophages, T cells, and natural killer (NK) cells. In a previous study, the combination of immunotherapy with the maitake D-Fraction and chemotherapy suggested that the D-Fraction may have the potential to decrease the size of lung, liver, and breast tumors in cancer patients. In the present study, we administered maitake D-Fraction to cancer patients without anticancer drugs, and at the same time NK cell activity was monitored to investigate whether the activity is closely related with disease progression. The numbers of CD4(+) and CD8(+) cells in the peripheral blood were measured in 10 patients, and NK cell activity was assessed using K-562 cells as target cells. Serum soluble interleukin-2 receptor (sIL-2R) levels in three patients and the expression of tumor markers in four patients were determined by enzyme-linked immunosorbent assay. The slight changes observed in the CD4(+) and CD8(+) cell numbers were independent of disease severity or stage as well as serum sIL-2R levels. In contrast, maitake D-Fraction hindered metastatic progress, lessened the expression of tumor markers, and increased NK cell activity in all patients examined. Thus maitake D-Fraction appears to repress cancer progression and primarily exerts its effect through stimulation of NK activity. In addition, we conclude that measurement of NK cell activity may be a useful clinical parameter in monitoring disease progression during and following immunotherapy with maitake D-Fraction.

Impaired TCR-mediated induction of Ki67 by naive CD4+ T cells is only occasionally corrected by exogenous IL-2 in HIV-1 infection

Perturbations in naive T cell homeostasis and function may play a major role in the immunodeficiency that accompanies HIV infection. By examining naive CD4(+) T cell function on a single cell basis, we provide evidence that these cells have significant qualitative defects in HIV disease. Ki67, a molecule expressed during cell cycle progression, is induced less efficiently among naive CD4(+) T cells from HIV-infected individuals following activation with anti-TCR Ab. The impairment in Ki67 expression is evident even when a separate function, CD62L down-modulation, is within normal ranges. Moreover, the defects in Ki67 induction are only sometimes corrected by the addition of rIL-2 to cell cultures. An initial assessment of IL-2 unresponsiveness in cells from selected HIV-infected individuals suggests that the defect is not a consequence of impaired IL-2R expression or IL-2R signaling capability. Qualitative defects in naive T cells that cannot be routinely corrected by IL-2 have significant implications for disease pathogenesis and for strategies using IL-2 as a vaccine adjuvant in HIV disease.

Specific Signaling Pathways Triggered by IL-2 in Human Vγ9Vδ2 T Cells: An Amalgamation of NK and αβ T Cell Signaling

The global immune response can be simplified into two components: the innate and the acquired systems. The innate immune response comprises primarily macrophages and NK cells, while B and T cells orchestrate the acquired response. Human Vgamma9Vdelta2 T cells represent a minor T cell subpopulation in blood (1-5%) that is activated via the TCR by small nonpeptidic molecules. Their percentage dramatically increases during the early phase of infection by intracellular pathogens, and they display many characteristics of NK cells, which places them at a unique position within the immune system. Our aim was to explore the behavior of these cells when they are activated by a receptor that is common to NK and alphabeta T cells, and to determine signaling pathways and biological responses induced in these cells through this receptor. Thus, we investigated whether Vgamma9Vdelta2 T cells behave as NK cells or as alphabeta T cells. We demonstrated that IL-2 activates not only STAT3, STAT5, the phosphatidylinositol 3-kinase pathway, and extracellular signal-regulated kinase-2 pathway, but also STAT4 as in NK cells, and the p38 mitogen-activated protein kinase pathway as in alphabeta T cells. Moreover, IL-2 induces the production of IFN-gamma in Vgamma9Vdelta2 T cells as observed in NK cells. Due to their double profiles, Vgamma9Vdelta2 T cells are at the interface of the innate and the acquired immune response and may therefore not only modulate the activity of innate cells, but also influence Th1/Th2 differentiation.

Fusion of interleukin-2 to subunit antigens increase their antigenicity in vitro due to an interleukin-2 receptor beta-mediated antigen uptake mechanism

Subunit vaccines, based on one or more epitopes, offer advantages over whole vaccines in terms of safety but are less antigenic. We investigated whether fusion of the cytokine interleukin-2 (IL-2) to influenza-derived subunit antigens could increase their antigenicity. The fusion of IL-2 to the subunit antigens increased their antigenicity in vitro. Encapsulation of the subunit antigen in liposomes also increased its antigenicity in vitro, yet encapsulation of the subunit IL-2 fusion did not. The use of anti-IL-2 receptor beta (IL-2Rbeta) antibody to block the receptor subunit on macrophages suggested that the adjuvancy exerted by IL-2 in our in vitro system is due to, at least in part, a previously unreported IL-2Rbeta-mediated antigen uptake mechanism.