Expression and function of the IL-2 receptor in activated human plasmacytoid dendritic cells

Biomarkers of systemic inflammation, soluble IL-2Rα and the multiple sclerosis-associated IL2RA SNP rs2104286 in healthy subjects and multiple sclerosis patients

Soluble interleukin-2 (IL-2) receptor α (sIL-2Rα) antagonizes IL-2 signaling and is involved in the pathogenesis of several immune-mediated diseases including multiple sclerosis (MS). The level of sIL-2Rα is affected by the MS-associated single nucleotide polymorphism (SNP) rs2104286. By use of ELISA and electrochemiluminescence, we investigated if 26 biomarkers of systemic inflammation were associated with sIL-2Rα and rs2104286 in cohorts of healthy subjects and MS patients in serum and heparin plasma. We found that sIL-2Rα significantly correlated with the level of tumor necrosis factor-α (TNFα) (r = 0.391, p = 0.002) in healthy subjects and the association was validated in a separate cohort. Additional, in healthy subjects we confirmed a previous report indicating that C-reactive protein (CRP) correlates with sIL-2Rα (r = 0.278, p = 0.034). None of the biomarkers of systemic inflammation were significantly associated with sIL-2Rα in MS patients. Furthermore, the MS-associated SNP rs2104286 was not significantly associated with any of the biomarkers of systemic inflammation in neither healthy subjects nor MS patients. We conclude that sIL-2Rα is associated with TNFα and CRP in healthy subjects. However, further research is required to confirm the use of sIL-2Rα as biomarker of systemic inflammation as well as to assess the mechanism underlying the observed correlation between levels of sIL-2Rα and TNFα.

Autophagic induction modulates splenic plasmacytoid dendritic cell mediated immune response in cerebral malarial infection model

Splenic plasmacytoid dendritic cells (pDC) possess the capability to harbor live replicative Plasmodium parasite. Isolated splenic pDC from infected mice causes malaria when transferred to naïve mice. Incomplete autophagic degradation might cause poor antigen processing and poor immune response. Induction of autophagic flux by rapamycin treatment led to better prognosis by boosting pDC centered immune response against the pathogen. Splenic pDC from rapamycin-treated infected mice, caused less parasitemia in naïve mice. The downregulation of adhesion with unaltered phagocytic potential of the cells post autophagic induction restricted excessive parasite burden within them. Rapamycin-treated pDC played a better role in antigen presentation. They showed higher expression of co-stimulatory molecules CD80, CD86, DEC205, MHCI. Rapamycin-treated pDC induced CD28 expression on CD8⁺ T cells and suppressed FasL level. This cells also influenced differentiation of effector, memory T cell population. The increase in IL10: TNFα ratio, Treg: Th17 ratio and lowering of myeloid DC: plasmacytoid DC ratio was observed. It shifted the overaggressive inflammation mediated Th1 pathway that is reported to incur host damage, to a better well-balanced cytokine profile exhibiting Th2 pathway. Autophagic flux induction within pDC proved to be beneficial in combating malarial pathogenicity.

Immunophenotypic characterization of human T cells after in vitro exposure to different silicone breast implant surfaces

The most common complication of silicone breast implants is capsular contracture (massive scar formation around the implant). We postulate that capsular contracture is always a sequel to inflammatory processes, with both innate and adaptive immune mechanisms participating. In general, fibroblasts and macrophages have been used as cell types to evaluate in vitro the biocompatibility of breast implant surfaces. Moreover, also T cells have been found at the implant site at the initial stage of fibrous capsule formation. However, only few studies have addressed the influence of surfaces with different textures on T-cell responses. The aim of the present study was to investigate the immune response of human peripheral blood mononuclear cells (PBMC) to commercially available silicone breast implants in vitro. PBMC from healthy female blood donors were cultured on each silicone surface for 4 days. Proliferation and phenotype of cultured cells were assessed by flow cytometry. Cytokine levels were determined by multiplex and real-time assay. We found that silicone surfaces do not induce T-cell proliferation, nor do they extensively alter the proportion of T cell subsets (CD4, CD8, naïve, effector memory). Interestingly, cytokine profiling identified matrix specific differences, especially for IL-6 and TNF-α on certain surface topographies that could lead to increased fibrosis.

Pleiotropic Effects of IL-2 on Cancer: Its Role in Cervical Cancer

IL-2 receptor (IL-2R) signalling is critical for normal lymphocyte proliferation, but its role in cervical cancer is not fully understood. The receptor is composed of three chains: IL-2α, IL-2β, and IL-2γ. Intracellular signalling is initiated by ligand-induced heterodimerization of the IL-2β and IL-2γ chains, resulting in the activation of multiple intracellular kinases. Recently, IL-2R was shown to be expressed on nonhaematopoietic cells, especially on several types of tumour cells. However, the function of this receptor on malignant cells has not been clearly defined. The expression of IL-2R and the production of IL-2 in cervical cancer cells have been documented as well as expression of molecules of the JAK-STAT pathway. In the current review we have highlighted the differences in the responses of molecules downstream from the IL-2R in normal lymphocytes and tumour cells that could explain the presence of tumour cells in an environment in which cytotoxic lymphocytes also exist and compete and also the effect of different concentrations of IL-2 that could activate effector cells of the immune system cells, which favour the elimination of tumour cells, or concentrations that may promote a regulatory microenvironment in which tumour cells can easily grow.

Increased expression with differential subcellular location of cytidine deaminase APOBEC3G in human CD4(+) T-cell activation and dendritic cell maturation

APOBEC3G (apolipoprotein B mRNA editing enzyme catalytic polypeptide-like 3G; A3G) is an innate defense protein showing activity against retroviruses and retrotransposons. Activated CD4(+) T cells are highly permissive for HIV-1 replication, whereas resting CD4(+) T cells are refractory. Dendritic cells (DCs), especially mature DCs, are also refractory. We investigated whether these differences could be related to a differential A3G expression and/or subcellular distribution. We found that A3G mRNA and protein expression is very low in resting CD4(+) T cells and immature DCs, but increases strongly following T-cell activation and DC maturation. The Apo-7 anti-A3G monoclonal antibody (mAb), which was specifically developed, confirmed these differences at the protein level and disclosed that A3G is mainly cytoplasmic in resting CD4(+) T cells and immature DCs. Nevertheless, A3G translocates to the nucleus in activated-proliferating CD4(+) T cells, yet remaining cytoplasmic in matured DCs, a finding confirmed by immunoblotting analysis of cytoplasmic and nuclear fractions. Apo-7 mAb was able to immunoprecipitate endogenous A3G allowing to detect complexes with numerous proteins in activated-proliferating but not in resting CD4(+) T cells. The results show for the first time the nuclear translocation of A3G in activated-proliferating CD4(+) T cells.

A novel modulation of structural and functional changes of mouse bone marrow derived dendritic cells (BMDCs) by interleukin-2(IL-2)

IL-2 is a pleiotropic cytokine produced by T cell after antigen activation of T cell and it is so called T cell growth factor. A large number of documents suggest that Il-2 plays pivotal roles in the immune response and now Il-2 is an approved drug being used for various kinds of diseases such as cancer and dermatitis. (1) The aim of present exploration was to look at effect of IL-2 on structural, phenotypic and functional maturation of murine BMDCs. The structural and phenotypic maturation of BMDCs under influence of IL-2 were evaluated by light microscope and flow cytometry (FCM). The functional maturation of BMDCs was confirmed by cytochemistry assay, FITC-dextran, acid phosphatase (ACP) activity, bio-assay and enzyme linked immunosorbent assay (ELISA).We elucidated that IL-2 up-regulated the expression of key surface markers such as: CD80, CD83, CD86, CD40 and MHC II molecules on BMDCs, down-regulated phagocytosis activity, induced more production of IL-12 and TNF-α secreted by BMDCs. Therefore it can be concluded that IL-2 effectively enhance the maturation of BMDCs. Our results provide direct evidence to support IL-2 would be used as a potent adjuvant in preparation of DC-based vaccines, as well as an immune remedy for cancer situation.

Improving Bacillus Calmette-Guérin (BCG) immunotherapy for bladder cancer by adding interleukin 2 (IL-2): a mathematical model

One of the treatments offered to non-invasive bladder cancer patients is BCG instillations, using a well-established, time-honoured protocol. Some of the patients, however, do not respond to this protocol. To examine possible changes in the protocol, we provide a platform for in silico testing of alternative protocols for BCG instillations and combinations with IL-2, to be used by urologists in planning new treatment strategies for subpopulations of bladder cancer patients who may benefit from a personalized protocol. We use a systems biology approach to describe the BCG-tumour-immune interplay and translate it into a set of mathematical differential equations. The variables of the equation set are the number of tumour cells, bacteria cells, immune cells, and cytokines participating in the tumour-immune response. Relevant parameters that describe the system's dynamics are taken from a variety of independent literature, unrelated to the clinical trial results assessed by the model predictions. Model simulations use a clinically relevant range of initial tumour sizes (tumour volume) and tumour growth rates (tumour grade), representative of a virtual population of fifty patients. Our model successfully retrieved previous clinical results for BCG induction treatment and BCG maintenance therapy with a complete response (CR) rate of 82%. Furthermore, we designed alternative maintenance protocols, using IL-2 combinations with BCG, which improved success rates up to 86% and 100% of the patients, albeit without considering possible side effects. We have shown our simulation platform to be reliable by demonstrating its ability to retrieve published clinical trial results. We used this platform to predict the outcome of treatment combinations. Our results suggest that the subpopulation of non-responsive patients may benefit from an intensified combined BCG IL-2 maintenance treatment.

Dendritic cell derived IL-2 inhibits survival of terminally mature cells via an autocrine signaling pathway

DCs are crucial for sensing pathogens and triggering immune response. Upon activation by pathogen-associated molecular pattern (PAMP) ligands, GM-CSF myeloid DCs (GM-DCs) secrete several cytokines, including IL-2. DC IL-2 has been shown to be important for innate and adaptive immune responses; however, IL-2 importance in DC physiology has never been demonstrated. Here, we show that autocrine IL-2 signaling is functional in murine GM-DCs in an early time window after PAMPs stimulation. IL-2 signaling selectively activates the JAK/STAT5 pathway by assembling holo-receptor complexes at the cell surface. Using the sensitivity of targeted mass spectrometry, we show conclusively that GM-DCs express CD122, the IL-2 receptor β-chain, at steady state. In myeloid DCs, this cytokine pathway inhibits survival of PAMP-matured GM-DCs which is crucial for maintaining immune tolerance and preventing autoimmunity. Our findings suggest that immune regulation by this novel autocrine signaling pathway can potentially be used in DC immunotherapy.

IL-2 phosphorylates STAT5 to drive IFN-γ production and activation of human dendritic cells

Human dendritic cells (hDCs) produce IL-2 and express IL-2R α-chain (CD25), but the role of IL-2 in DC functions is not well defined. A recent study suggested that the main function of CD25 on hDCs was to transpresent IL-2 to activate T lymphocytes. Our results demonstrate the expression of the three chains of the IL-2R on hDCs and that IL-2 induces STAT5 phosphorylation. Interestingly, use of inhibitors of p-STAT5 revealed that IL-2 increases LPS-induced IFN-γ through STAT5 phosphorylation. Finally, we report that IL-2 increases the ability of hDCs to activate helpless CD8(+) T cells, most likely because of IL-2-triggered IFN-γ synthesis, as we previously described. For the first time, to our knowledge, we disclose that IL-2 induces monocyte-derived hDC's functional maturation and activation through IL-2R binding. Interestingly, our study suggests a direct effect of anti-CD25 mAbs on hDCs that may contribute to their clinical efficacy.

Priming of T follicular helper cells by dendritic cells

T follicular helper cells (Tfh) are required to generate long-lived antibody responses, which confer long-term protection to pathogens following vaccination or infection. Despite significant advances in the field, however, little is known about the early steps that drive Tfh cell differentiation. In this review, we will discuss the mechanisms by which dendritic cells promote the initial commitment of activated CD4(+) T cells to the Tfh cell differentiation pathway.

Interleukin-2 at the crossroads of effector responses, tolerance, and immunotherapy

Interleukin-2 (IL-2) is a pleiotropic cytokine produced after antigen activation that plays pivotal roles in the immune response. Discovered as a T cell growth factor, IL-2 additionally promotes CD8(+) T cell and natural killer cell cytolytic activity and modulates T cell differentiation programs in response to antigen, promoting naïve CD4(+) T cell differentiation into T helper 1 (Th1) and T helper 2 (Th2) cells while inhibiting T helper 17 (Th17) and T follicular helper (Tfh) cell differentiation. Moreover, IL-2 is essential for the development and maintenance of T regulatory cells and for activation-induced cell death, thereby mediating tolerance and limiting inappropriate immune reactions. In this review, we focus on the molecular mechanisms and complex cellular actions of IL-2, its cooperative and opposing effects with other cytokines, and how both promoting and blocking the actions of IL-2 are being utilized in clinical medicine.

Differential effect of CD69 targeting on bystander and antigen-specific T cell proliferation

In spite of an initially proposed role as a costimulatory molecule for CD69, in vivo studies showed it as a regulator of immune responses and lymphocyte egress. We found constitutive CD69 expression by T cell subsets and pDC. We examined a possible effect of CD69 on T cell proliferation using transfer models and in vitro assays. In mice locally expressing or receiving antigen, anti-CD692.2 treatment did not affect the proliferation of antigen-specific transgenic T cells in ADLN, although we observed the presence of proliferated T cells in non-ADLN and spleen. This was not affected by FTY720 treatment and thus, not contributed by increased egress of proliferated lymphocytes from ADLN. In the absence of antigen, anti-CD69 2.2 treatment induced bystander proliferation of transferred memory phenotype T cells. This proliferation was mediated by IL-2, as it was inhibited by anti-IL-2 or anti-CD25 antibodies in vitro and by anti-CD25 antibodies in vivo. It was also dependent on CD69 expression by donor T cells and recipient cells. CD69 targeting on T cells enhanced IL-2-mediated proliferation and CD25 expression. However, it did not lead to increased early IL-2 production by T cells. No T cell subset was found to be specifically required in the recipient. Instead, CD69 targeting on pDC induced their expression of IL-2 and CD25, and pDC depletion showed that this subset was involved in the proliferation induction. These results indicate that CD69 targeting induces bystander T cell proliferation through pDC IL-2 production and T cell sensitization to IL-2 without affecting antigen-driven T cell proliferation.

Ligation of Notch receptors in human conventional and plasmacytoid dendritic cells differentially regulates cytokine and chemokine secretion and modulates Th cell polarization

Notch signaling is involved in multiple cellular processes. Recent data also support the prominent role of Notch signaling in the regulation of the immune response. In this study, we analyzed the expression and function of Notch receptors and ligands on both human blood conventional dendritic cells (cDCs) and plasmacytoid DCs (pDCs). The expression and modulation upon TLR activation of Notch molecules partially differed between cDCs and pDCs, but functional involvement of the Notch pathway in both cell types was clearly revealed by specific inhibition using DAPT. Beyond the induction of Notch target genes and modulation of maturation markers, Notch pathway was also involved in a differential secretion of some specific cytokines/chemokines by DC subsets. Whereas Notch ligation induced IL-10 and CCL19 secretion in cDCs, Notch inhibition resulted in a diminished production of these proteins. With regard to pDCs, Notch activation induced TNF-α whereas Notch inhibition significantly abrogated the secretion of CCL19, CXCL9, CXCL10, and TNF-α. Additionally, Notch modulation of DC subsets differentially affected Th polarization of allostimulated T cells. Our results suggest that the Notch pathway may function as an additional mechanism controlling human DC responses, with differential activity on cDCs and pDCs. This control mechanism may ultimately contribute to define the local milieu promoted by these cells under the particular conditions of the immune response.

Expression of the T cell receptor αβ on a CD123+ BDCA2+ HLA-DR+ subpopulation in head and neck squamous cell carcinoma

Human Plasmacytoid Dendritic Cells (PDCs) infiltrating solid tumor tissues and draining lymph nodes of Head and Neck Squamous Cell Carcinoma (HNSCC) show an impaired immune response. In addition to an attenuated secretion of IFN-α little is known about other HNSCC-induced functional alterations in PDCs. Particular objectives in this project were to gain new insights regarding tumor-induced phenotypical and functional alterations in the PDC population. We showed by FACS analysis and RT-PCR that HNSCC orchestrates an as yet unknown subpopulation exhibiting functional autonomy in-vitro and in-vivo besides bearing phenotypical resemblance to PDCs and T cells. A subset, positive for the PDC markers CD123, BDCA-2, HLA-DR and the T cell receptor αβ (TCR-αβ) was significantly induced subsequent to stimulation with HNSCC in-vitro (p = 0.009) and also present in metastatic lymph nodes in-vivo. This subgroup could be functionally distinguished due to an enhanced production of IL-2 (p = 0.02), IL-6 (p = 0.0007) and TGF-β (not significant). Furthermore, after exposure to HNSCC cells, mRNA levels revealed a D-J-beta rearrangement of the TCR-beta chain besides a strong enhancement of the CD3ε chain in the PDC population. Our data indicate an interface between the PDC and T cell lineage. These findings will improve our understanding of phenotypical and functional intricacies concerning the very heterogeneous PDC population in-vivo.

Characterization of the cytokine and maturation responses of pure populations of porcine plasmacytoid dendritic cells to porcine viruses and toll-like receptor agonists

Plausible representatives of plasmacytoid dendritic cells (pDCs) in pigs have been characterized as being CD4^hiCD172^lo. Due to their paucity in blood, we utilized novel fluorescent-activated cell sorting procedures to isolate them from PBMC. The resultant subset was greater than 98% homogeneous in regards to the selected phenotype and contained the preponderance of individuals secreting IFN-α after exposure to a known stimulant, transmissible gastroenteritis virus (TGEV). In addition to being a potent source of IFN-α, other properties of these porcine CD4^hiCD172^lo cells including their morphological transition from a plasma cell-like shape during quiescence to one resembling a dendritic cell (DC) after activation by TGEV and their relatively strong constitutive expression of interferon regulatory factor-7 (IRF-7) conformed to the expectations of genuine pDCs. While a substantial IFN-α response was also elicited from the porcine pDCs by pseudorabies virus (PrV), swine influenza virus (SIV), and TLR7 and 9 agonists, there was an agent-dependent induction of varying amounts of IL-2, IL-6, IL-8, IL-12, IFN-γ, and TNF-α. Notably, porcine reproductive and respiratory syndrome virus (PRRSV) failed to provoke the pDCs to secrete any of the measured cytokines except IL-2. Moreover, whereas pDCs exposed to TGEV or the TLR9 agonist rapidly increased IRF-7 production and morphed into DCs with enhanced CD80/86 expression, similar alterations were not observed during incubation with PRRSV. This atypical response of pDCs to PRRSV may contribute to its pathogenesis, which unlike that associated with PrV, SIV or TGEV includes persistent infection and limited development of protective immunity.

CD25 as an immune regulatory molecule expressed on myeloid dendritic cells

CD25 (alpha-chain of IL-2 receptor) on dendritic cells (DC) has been previously regarded as an activation marker. DC that concomitantly express surface CD25 and co-stimulatory molecules were considered to be fully mature. While both murine and human DC can express CD25, they do not express the beta-chain of the IL-2 receptor, which is indispensable for the execution of IL-2 signaling. The biological function of CD25 during the DC maturation therefore still remains undefined. In this review we focus on recent findings, describing CD25 expression and secretion by human myeloid regulatory DC. These DC co-express CD25 and the immunoregulatory enzyme indoleamine 2,3-dioxygenase (IDO) and inhibit T-cell function. CD25, expressed and secreted by such DC may capture IL-2 and thereby suppress T-cell proliferation, by this means providing an accessory mechanism of DC-mediated immune suppression. We also discuss the implication of DC-derived CD25 for human disease in both cancer and chronic infection.

The IL-2/CD25 pathway determines susceptibility to T1D in humans and NOD mice

Although the interleukin-2 (IL-2)/IL-2R signaling pathway has been the focus of numerous studies, certain aspects of its molecular regulation are not well characterized, especially in non-T cells, and a more complete understanding of the pathway is necessary to discern the functional basis of the genetic association between the IL-2-IL-21 and IL-2RA/CD25 gene regions and T1D in humans. Genetic variation in these regions may promote T1D susceptibility by influencing transcription and/or splicing and, hence, IL-2 and IL-2RA/CD25 expression at the protein level in different immune cell subsets; thus, there is a need to establish links between the genetic variation and immune cell phenotypes and functions in humans, which can be further investigated and validated in mouse models. The detection and characterization of genetically determined immunophenotypes should aid in elucidating disease mechanisms and may enable future monitoring of disease initiation and progression in prediabetic subjects and of responses to therapeutic intervention.

Anti-CD25 antibodies affect cytokine synthesis pattern of human dendritic cells and decrease their ability to prime allogeneic CD4+ T cells

Anti-CD25 monoclonal antibodies are widely used in clinical transplantation to prevent acute allograft rejection. Although their effects on T lymphocytes have been extensively studied, their impact on human dendritic cells (DC) has never been reported. Furthermore, the role of the IL-2 in DC functions has not yet been fully elucidated. In this study, we confirm that the stimulation of human monocyte-derived DC with LPS strongly induced the expression of CD25 and that LPS-matured DC also expressed the beta and gamma chain of the IL-2R. We also showed that adding anti-CD25 monoclonal antibodies to LPS induced a decrease in IL-12, IL-1, TNF-alpha, IL-6, and IFN-gamma production and an increase in IL-10 synthesis by DC compared with stimulation with LPS alone. Furthermore, we showed that these modifications diminished the T helper priming ability of DC and polarized the alloimmune response toward TH2. In contrast, humanized anti-CD25 monoclonal antibodies did not affect the up-regulation of CD86, CD80, CD83, HLADR, or CD40 induced upon LPS stimulation. Taken together, this study discloses some previously unrecognized effects of anti-CD25 monoclonal antibodies on DC that may contribute to their clinical efficacy. In addition, this study also shed some light on the role of the IL-2 in human DC activation.

The regulatory, inflammatory, and T cell programming roles of interleukin-2 (IL-2)

Signaling through IL-2 induces the activation of pathways that lead to the proliferation, survival and cytokine production of effector T cells. However, through negative feedback mechanisms, internalization of the IL-2 receptor, induction of activation-induced cell death, and the generation of regulatory T cells, IL-2 also promotes the suppression of inflammatory responses. In regulatory T cells, IL-2 signaling upregulates the expression of FoxP3. Regulatory T cell induction by TGF-beta also requires IL-2. Additionally, pro-inflammatory and pro-survival pathways involving PI3K upon IL-2 stimulation is inhibited by PTEN in regulatory T cells. Importantly, IL-2 signaling is key for the development, expansion and maintenance of regulatory T cells. However, gamma(c) cytokines can replace requirements for IL-2 in regulatory T cells, although not with the same efficacy. The dual roles of IL-2 in inflammation are demonstrated in that mice deficient in both FoxP3 and IL-2 display less severe symptoms compared to FoxP3 deficient mice. Finally, IL-2 not only plays a key role in the induction of effector T cells and regulatory T cells, it also inhibits IL-17 producing T cells. By understanding complex dynamics of IL-2 interactions in the inflammatory response, therapies may be developed or modified for regulating immune related diseases.

Large-scale genetic fine mapping and genotype-phenotype associations implicate polymorphism in the IL2RA region in type 1 diabetes

Genome-wide association studies are now identifying disease-associated chromosome regions. However, even after convincing replication, the localization of the causal variant(s) requires comprehensive resequencing, extensive genotyping and statistical analyses in large sample sets leading to targeted functional studies. Here, we have localized the type 1 diabetes (T1D) association in the interleukin 2 receptor alpha (IL2RA) gene region to two independent groups of SNPs, spanning overlapping regions of 14 and 40 kb, encompassing IL2RA intron 1 and the 5' regions of IL2RA and RBM17 (odds ratio = 2.04, 95% confidence interval = 1.70-2.45; P = 1.92 x 10(-28); control frequency = 0.635). Furthermore, we have associated IL2RA T1D susceptibility genotypes with lower circulating levels of the biomarker, soluble IL-2RA (P = 6.28 x 10(-28)), suggesting that an inherited lower immune responsiveness predisposes to T1D.