IL-2R Alpha Chain Research Articles

P1425: ACTIVATED AND EXPANDED NATURAL KILLER CELLS TRANSDUCED WITH AN NKG2D CHIMERIC ANTIGEN RECEPTOR AGAINST ACUTE MYELOID LEUKEMIA

Background: Acute Myeloid Leukemia (AML) is a hematological malignancy incurable for almost all patients. Chimeric Antigen Receptor (CAR) therapy is showing promising results in other hematological disorders but remains challenging in AML since no specific antigens have been described yet. Using NKG2D as a CAR, a natural NK receptor with 8 ligands overexpressed in several tumors, could surmount AML targeting limitations. T cells are considered the gold standard immune effector cells for CAR therapy, but they show toxicities that could be overcome using other cells such as activated and expanded natural killer cells (NKAE), that can be used in an allogeneic context with no GvHD, have natural anti-tumor properties and a short lifespan within the organism. In this project we analyze the in vitro efficacy and security of peripheral blood NKAE cells lentivirally transduced with an NKG2D-41BB-CD3z CAR. Aims: The primary objective of this project is to assess the efficacy and security of a cell immunotherapy against AML based on the use of NKAE cells transduced with an NKG2D CAR. Methods: NKAE cells were isolated from peripheral blood mononuclear cells (PBMCs) of healthy donors (HD) and/or AML patients after 7 days of coculture with the irradiated cell line k562-mb21-41BBL by magnetic immunodepletion, when they were transduced with lentiviral vectors carrying NKG2D-41BB-CD3z CAR construct. CAR expression was measured up to 15 days post-transduction by flow cytometry. Cytotoxic activity against AML cell lines was performed by Propidium Iodide and Annexin V staining. Toxicity was evaluated by Europium-TDA assays. Results: AML can be targeted with an NKG2D CAR since all patients studied expressed at least one NKG2DL (Fig.1). Primary NK cells can be lentivirally transduced with an NKG2D CAR, showing a modest but stable CAR expression up to 15 days after transduction (23% ±4,7% NKG2D+, 33,35% ±4,25% GFP+). CAR-NKAE cells perform robust cytotoxicity towards MOLM-13 AML cell line after 24h of coculture at an effector:target ratio of 1:1, exerting a quasi-total lysis of AML cells (Fig.2A). This represents a significant increase in anti-leukemia effect compared to untransduced NKAE (92,6% ±0,3% vs 72,2% ±10%, p= 0,0138). Surface expression of relevant molecules for NK activity showed that NKp30, NKp44 (natural cytotoxicity receptors), CD69 (early activation marker), CD25 (IL2R alpha chain), FasL (mediates FasL-mediated cytotoxicity), NKp80 (C-type lectin-like surface-activating receptor) and TRAIL (TNF-Related Apoptosis Inducing Ligand) were more expressed by transduced NKAE (Fig.2B). Cytokine release profile revealed a higher production of IL-6, IL-17A, sFasL and IFNg by CAR-NKAE (Fig.2C). We did not observe relevant toxic effects of none of the cells against healthy PBMCs and very low toxicities were found against NL-20 lung cell line, but there were no differences between NKAE and CAR-NKAE. Image:Summary/Conclusion: Our preliminary results show that primary NK cells can be lentivirally transduced with a second generation NKG2D CAR, exerting a robust anti-leukemia activity towards AML cell lines. Transduced cells show a more cytotoxic immunophenotype as well as a higher release of cytolytic molecules and proinflammatory and proapoptotic proteins, that could be responsible of the increased anti-tumor response. Hence, NKG2D-CAR transduced NKAE cells could be a suitable approach to treat AML. Other costimulatory domains are being studied in order to assess which one triggers a higher cytotoxic activity, thus allowing decreasing the effector:target ratios and therefore, on-target off-tumor effect.

Tumour immune evasion mechanism in non-small cell lung cancer by inducing Blimp-1 in CD4+CD25+Foxp-3+ T regulatory cells

Abstract Immunotherapy improves the life expectancy of patients with lung cancer by targeting the immune inhibitory T cell surface markers resulting in the activation of anti-tumor T cell survival and suppression of tumor cell growth. The transcription factor repressor Positive Regulatory Domain Containing Protein 1 (encoded in humans by the Prdm1 gene) also known as B lymphocytes-induced maturation protein-1 (Blimp-1) affects the homeostasis and function of CD4+ and CD8+ T cells as well as T regulatory cells (T regs). We recently reported that Blimp-1 is induced in the lung tumoral region of patients with lung ADC. To further investigate whether Blimp-1 could be a candidate gene involved in the regulation of the anti-tumor immune-response in lung cancer, we started to investigate peripheral blood mononuclear cells (PBMCs) isolated from healthy control subjects and NSCLC patients for Blimp-1 expression in immunosuppressive CD4+CD25+Foxp3+ T regs. The PBMCs were cultured with and without antiCD3/CD28 antibodies, without and with TGF-beta, to mimic the tumor microenvironment, for 4 days and subsequently analyzed by flow cytometry using antibodies against Blimp-1, Foxp3, CD4 and CD25(IL-2R alpha chain). Here we found, by trend, induced CD4+Blimp1+CD25+Foxp3+ Tregs in unstimulated PBMCs from patients with lung cancer. Moreover, TGF-beta further induced these Blimp1+CD4+CD25+Foxp3+ Tregs in PBMCs obtained both from healthy controls and from NSCLC patients. Taken together these data indicate that the tumor microenvironment induces Blimp-1 in immunosuppressive CD4+CD25+Foxp3+ Tregs via TGF-beta. Thus, current immunotherapy should be combined to TGF-beta inhibitors to target CD4+CD25+Blimp1+Foxp-3+ T regulatory cells.

Super2-expressing CAR T cells generate improved anti-tumor responses against solid tumors

Abstract Chimeric antigen receptors (CAR) augment tumor specific immune responses by redirecting all T cells towards recognition of tumor antigen. Although CAR T cell treatment shows promising therapeutic effects in leukemia patients, current CAR therapies are inadequate against solid tumors, in part from exclusion or functional exhaustion in the suppressive microenvironment. Exogenously administered Interleukin 2 (IL-2) improves efficacy and expansion of CAR T cell therapy. However, IL-2 administration is limited by high toxicity and low half-life. Super2 is an engineered IL-2 variant that binds with high affinity to the beta and gamma chains of the IL-2 receptor even without IL-2R alpha chain expression. We found that Super2 leads to increased phosphorylation of STAT-5 and more effectively activates lymphocyte populations compared to endogenous IL-2 in vitro. We hypothesized that engineering CAR T cells to express Super2 will improve their functionality within the tumor microenvironment. CAR T cell-intrinsic Super2 may also increase activation of the endogenous tumor-reactive T cells resulting in enhanced tumor control and the establishment of long-term memory even after loss of CAR T cells. To test this hypothesis, we designed CAR T cells that produce Super2 constitutively or in response to CAR stimulation. We found that Super2-expressing CAR T cells increased tumor infiltrating leukocytes (TILs) compared to CAR T cell treatment alone in immune competent murine models. Additionally, Super2-expressing CAR T cells delayed B16F10 melanoma growth in comparison to CAR T cell alone. We conclude that Super2-expressing CAR T cells provide improved protection against solid tumors.

CD73 Rather Than CD39 Is Mainly Involved in Controlling Purinergic Signaling in Calcified Aortic Valve Disease.

The study aimed to compare composition of peripheral blood T-cell subsets and assess their surface expression of CD39 and CD73 ectonucleotidases in patients with severe and moderate aortic stenosis (AS) as well as to evaluate involvement of T-cell-mediated immune processes in valve calcification. The study was performed with 38 patients suffering from severe calcified aortic stenosis (SAS), 33 patients with MAS, and 30 apparently healthy volunteers (HVs). The relative distribution and percentage of T-cell subsets expressing CD39 and CD73 were evaluated by flow cytometry. T helper (Th) and cytotoxic T-cell subsets (Tcyt) were identified by using CD3, CD4, and CD8 antibodies. Regulatory T cells (Tregs) were characterized by the expression of CD3, CD4, and high IL-2R alpha chain (CD25high) levels. CD45R0 and CD62L were used to assess differentiation stage of Th, Tcyt, and Treg subsets. It was found that MAS and SAS patients differed in terms of relative distribution of Tcyt and absolute number of Treg. Moreover, the absolute number of Tcyt and terminally differentiated CD45RA-positive effector T-cells (TEMRA) subset was significantly higher in SAS vs. MAS patients and HVs. However, the absolute and relative number of naïve Th and the absolute number of Treg were significantly higher in MAS vs. SAS patients; the relative number of naïve Tregs was significantly (p < 0.01) decreased in SAS patients. It was shown that CD73 expression was significantly higher in SAS vs. MAS patients noted in all EM, CM, TEMRA, and naïve Th cell subsets. However, only the latter were significantly increased (p = 0.003) in patients compared with HVs. SAS vs. MAS patients were noted to have significantly higher percentage of CD73+ EM Tcyt (p = 0.006) and CD73+ CM Tcyt (p = 0.002). The expression of CD73 in patients significantly differed in all three Treg populations such as EM (p = 0.049), CM (p = 0.044), and naïve (p < 0.001). No significant differences in CD39 expression level was found in MAS and SAS patients compared with the HV group. Overall, the data obtained demonstrated that purinergic signaling was involved in the pathogenesis of aortic stenosis and calcification potentially acting via various cell types, wherein among enzymes, degrading extracellular ATP CD73 rather than CD39 played a prominent role.

IL-6 overexpression triggers inflammation through its only relevant receptor IL-6R

Abstract IL-6 is a pleiotropic cytokine that regulates development and function of variety immune cells. Here we used a novel mouse strain in which IL-6 can be overexpressed in a Cre-dependent manner and show that mice with CD11c-Cre mediated IL-6 overexpression succumb from systemic inflammation. High levels of IL-6 perturbed B and T cell development in primary lymphoid organs, bone marrow and thymus. Interestingly, IL-6-triggered inflammation promoted expansion of both Th17 and Treg cells, two cell types known for their reciprocal developmental requirements. However, the most dramatic increase was noted for myeloid cells, mostly neutrophils, which invaded spleen, thymus and blood of mice with IL-6 overexpression. Observed systemic inflammation ultimately led to mice mortality within 11 weeks of age. Mechanistically, IL-6 mediates its biological functions strictly through binding to IL-6R alpha chain followed by recruitment of the signal transducer gp130. Previously, an alternative pathway was suggested in which IL-6 can utilize CD5 to signal via gp130. However, when IL-6R was deleted in mice with IL-6 overexpression these mice were completely protected from IL-6- triggered pathology and fully phenocopied IL-6R deficient mice. In fact, IL-6R deficiency prevented downstream activation of STAT3 in response to IL-6. Together, our data suggest that IL-6R is the only biological relevant receptor for IL-6 in mice.

Mechanism of action of NKTR-214, a first-in-class, CD122-preferential IL-2 pathway agonist

NKTR-214 is a first-in-class, CD122-preferential IL-2 pathway agonist that provides sustained activation of the IL-2 pathway via IL-2R beta chain-biased signaling, selectively stimulating CD8+ T cells over regulatory T cells (Tregs), which require binding to the IL-2R alpha chain. NKTR-214 has proven safe and effective in increasing CD8+ T cells in the circulation and in tumor tissue in patients with a variety of cancer, including melanoma, renal, lung, bladder and breast cancer. Interestingly, NKTR-214 dramatically decreased Treg levels in tumors, but not in the periphery. To better understand this phenomenon, we used a model of gp100 melanoma antigen-specific vaccination and gp100-specific pmel-1 T cells to study the impact of NKTR-214 treatment on CD8+ Teff and CD4+Foxp3+ Tregs. We found that NKTR-214 induced CD8+ T cell accumulation in tumor tissue as well as Treg depletion in tumor tissue but not in the circulation. Mechanistically, NKTR-214 treatment favored proliferation and survival of effector CD8+ T cells while reducing proliferation and promoting apoptosis of intratumoral Tregs. In vivo cytokine neutralization experiments and in vitro assays together with proteomic analysis of Tregs revealed that NKTR-214 plus vaccine treatment induced potent release of CD8+ T cell-associated cytokines IFN-γ and TNF-α, which synergized to induce Treg proliferative block and apoptosis by inhibiting IL-2 and TCR-downstream signaling. These results shed light on the mechanism of action of NKTR-214 and point to a mechanism of increased CD8+ T cell influx and temporal, localized Treg depletion at sites of strong effector T cell activity.

Abstract B118: Potentiation of IL-2’s antitumor efficacy without compromised tolerability by a novel human antibody

Abstract IL-2 was the first approved cancer immunotherapy and is still recognized for its durable responses. While IL-2 does mobilize relevant antitumor immune cells such as CD8+ T effector and activated NK cells, its utility is limited by parallel expansion of Treg cells and by dose-limiting toxicities. IL-2 Receptor alpha chain binding by IL-2 may be important in driving Treg expansion and some adverse side effects. Over the last decade, there have been approaches at modifying IL-2 structure-function or selecting antibodies that bind IL-2 and bias its activation of preferential cell types. One candidate (pegylated IL-2, NKTR-214) has moved into clinical development. XOMA mAb19 is a fully human monoclonal antibody to IL-2 that selectively compromises binding to IL-2R alpha chains, but not beta-gamma chains, thus potentially expanding IL-2’s antitumor therapeutic index. mAb19 binding characteristics and efficacy in a mouse Lewis Lung Carcinoma model were described at SITC 2016. In the current studies, a CT26 mouse colon carcinoma model was utilized to assess antitumor efficacy and tolerability of combined mAb19 + low-dose IL-2 dosing and to compare such with standard high-dose IL-2 regimens. The CT26 study results presented here demonstrate that mAb19 and IL-2 coadministration potentiates IL-2’s antitumor activity, expands CD8+ T effector and activated NK cells but not Treg cells, and is well tolerated. Specifically, treatment of tumor-bearing mice with about 1 mg/kg mAb19 plus about 0.1 mg/kg IL-2 yielded significant antitumor efficacy, which was at least as substantial as high-dose (e.g. 5 mg/kg) IL-2 regimens wherein significant body weight loss and ~10% mortality were observed. Notably, the mAb19 + IL-2 regimen had no dose-limiting toxicity. Moreover, the magnitude of antitumor response of the combination mAb19+IL2 was superior to that reported for NKTR-214 in the same model (AACR 2015). Preclinical development continues, including assessment for enhanced efficacy with checkpoint inhibitor(s). Citation Format: Kirk Johnson, Ou Li, Xiaohe Liu, Lucia Beviglia. Potentiation of IL-2’s antitumor efficacy without compromised tolerability by a novel human antibody [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B118.

Construction and Functional Analysis of Luciferase Reporter Plasmid Containing CD25 Gene Promoter

CD25 is the alpha chain of IL-2R and IL-2R is distributed on the surface of activated T cells, B cells, and NK cell. The transcriptional factor CD25 plays an important role in the proliferation and differentiation of Treg cells. MKL-1 is also called MAL (megakaryocytic acute leukemia) and belongs to the Myocardin family which also includes MKL-2 (megakaryoblastic leukemia 2) and Myocardin. Studies have shown that in the process of mouse megakaryocyte differentiation, the expression of MKL-1 is up-regulated, and MKL-1 promotes the physiological maturation of human and mouse megakaryocytes. However, the exact mechanism of the CD25 on megakaryocytes is unclear. In this study, human CD25 promoter luciferase reporter construct was generated by PCR amplification. Then the PCR fragment was digested and cloned into pGL3 vector, and this promoter sequence was verified by sequencing. The result showed that luciferase reporter with CD25 promoter was successfully constructed. The expression vectors of human MKL-1 were bought from addgene. Then the activation of the CD25 promoter was detected in 293T cells by luciferase reporter assay after transfected expression vectors of human MKL-1. The result showed that transfected the expression vectors can enhance the transcriptional activity of CD25. Our research will reveal the effect of CD25 on megakaryocytes and may provide a theoretical basis and therapeutic method for diseases caused by megakaryocytes.

Ligand–receptor dissociated expression explains high TSLP without prognostic impact in human primary head and neck squamous cell carcinoma

ABSTRACTThymic stromal lymphopoietin (TSLP) is an interleukin (IL)-7-like cytokine expressed by epithelial cells during allergic inflammation, and activating dendritic cells (DC). Its expression and functional role in cancer remain controversial. We conducted retrospective (n = 89), and prospective studies including patients with untreated primary head and neck squamous cell carcinoma (HNSCC). We found that TSLP was overexpressed by HNSCC tumor cells, and associated with a highly differentiated status. However, no significant difference in overall and recurrence-free survival was found between patients bearing a tumor with high and low TSLP levels, respectively. Surprisingly, there was no significant association between the levels of TSLP expression, and the number of tumor-infiltrating mature DCLAMP+ DC. In order to explain the apparent lack of TSLP-induced DC activation, we performed phenotypic and functional experiments on freshly resected tumors. Tumor-infiltrating immune cells, including DC, did not express the TSLP receptor heterodimer (TSLPR chain, IL-7Ralpha chain). Furthermore, freshly sorted blood CD11c+ DC from healthy donors cultured with tumor-conditioned supernatant exhibited an activated profile, but this was not affected by an anti-TSLP blocking antibody, suggesting a DC activation pathway independent of tumor-derived TSLP. Overall, our results demonstrate that TSLP is overexpressed in HNSCC but its function is hampered by the lack of TSLPR-expressing cells in the tumor microenvironment. Such a dissociated ligand–receptor expression may impact intercellular communication in other immune activation pathways, and tumor types.

Identification of a Neoplastic Stem Cell in Human Mast Cell Leukemia

Leukemic stem cells (LSCs) have recently been identified as an important target of therapy in various human leukemias and related blood cell disorders. Systemic mastocytosis (SM) is a rare hematologic neoplasm characterized by abnormal growth and accumulation of mast cells (MCs) in various organ systems, including the bone marrow (BM). Whereas patients with indolent SM (ISM) have a normal life-expectancy, patients with more advanced forms of SM have a poor prognosis. In these patients, neoplastic MCs are usually resistant against conventional drugs and various targeted drugs. MC leukemia (MCL) is the rare leukemic variant of advanced SM, defined by a rapidly devastating expansion of immature MCs in various hematopoietic organs and a poor prognosis with short survival times. Although MCL is considered a stem cell disease, little is known about the origin and phenotype of MCL-initiating LSCs. We examined the phenotypic and functional characteristics of putative LSCs in patients with aggressive SM (ASM, n=12) and MCL (n=6). Putative LSCs were identified and characterized phenotypically by flow cytometry. Highly enriched, sorted LSCs were injected into NOD-SCID-IL-2Rγ-/- mice exhibiting a 220 amino acid isoform of human membrane-bound hSCF (NSGSCF). We found that disease-initiating and propagating LSCs reside within a CD34+ fraction of the MCL clone. Whereas cell fractions containing CD34+ cells as well as highly enriched CD34+ cells produced engraftment in NSGSCF mice with a MCL-like disease (43-77% human MCL cells in mouse BM after 10-22 weeks), no substantial engraftment was produced by MC-rich but stem cell-depleted, KIT+/CD34─ cell fractions obtained from the same patients (<1% engraftment in mouse BM). In dilution experiments, engraftment of CD34+ cells was documented down to a minimum of 50 cells per mouse. The identity of engrafting MCL cells was confirmed by morphology, phenotyping and molecular studies demonstrating the presence of KIT mutations that were initially detected in the primary MCL samples used. Moreover, we were able to confirm long-term engraftment by successful serial transplantations into secondary recipient mice. In consecutive experiments, we were able to show that CD45+/CD34+/CD38─ cells also produce leukemic engraftment in NSGSCF mice. As assessed by flow cytometry, these CD34+/CD38─ MCL LSCs were found to express several stem cells markers, including aminopeptidase-N (CD13), leukosialin (CD43), Pgp-1 (CD44), the IL-3R alpha-chain (CD123), AC133 (CD133) and CXCR4 (CD184). In addition, in most patients examined, MCL LSCs were found to display IL-1RAP, a surface antigen that is otherwise expressed in CML LSCs but is not expressed in normal stem cells. In addition, MCL LSCs were found to express various cell surface targets, including CD33 and CD52. By contrast, MCL LSCs did not express CD2, CD25, CD26 and CLL-1. The more mature progenitor cell fractions (CD34+/CD38+) were found to stain positive for CD13, CD33, CD43, CD44, CD90, CD117, CD123, CD133 and CD184. Mature clonal MCs expressed a similar phenotype, including molecular markers and targets, such as CD13, CD30 CD33, CD52 and CD184. In patients with ISM and aggressive SM (ASM), the CD34+/CD38─ stem cells exhibited a similar surface marker profile compared to MCL, but expressed lower levels of CD133 and did not express IL-1RAP. In the validation phase of our study, we examined the effects of target-specific antibodies. As assessed by flow cytometry, the CD52-targeting antibody alemtuzumab was found to induce complement-dependent lysis of CD34+ and CD34+/CD38─ cells in all MCL samples analysed. Furthermore, pre-incubation of MCL cells with alemtuzumab prior to injection into NSGSCF mice resulted in a significantly reduced engraftment (2.7±4.1%) after 22 weeks. In conclusion, our data show that the MCL clone originates from a primitive hematopoietic stem cell that co-expresses CD34, CD123, CD133 and IL-1RAP but lacks CD25 and CD26. In addition, our data show that MCL LSC express a number of clinically relevant surface targets, including CD33, CD52 and CD117 (KIT). These observations may facilitate LSC detection and isolation in MCL and may lead to the development of novel LSC-eradicating treatment concepts in this highly aggressive and drug-resistant form of leukemia. DisclosuresValent:Novartis: Consultancy, Honoraria, Research Funding.

Abstract 1094: Role of the CRLF2 ligand TSLP in normal human B-cell development

Abstract B cell acute lymphoblastic leukemia (B-ALL) is the most common childhood malignancy. Defects that result in overexpression of CRLF2, a cytokine receptor component, have recently been linked with poor outcome in both high-risk and non-high-risk B-ALL. CRLF2, together with the IL-7R alpha chain, forms the signaling receptor for the cytokine TSLP (Thymic Stromal-derived LymphoPoietin). TSLP-induced CRLF2 signaling results in proliferation of murine B cell progenitors, however, the role of TSLP in murine B cell development remains controversial and little is known of its role in human B lymphopoiesis. Human TSLP and CRLF2, in contrast to other cytokine/receptor pairs that act on B cell progenitors, show low homology to their murine counterparts (&amp;lt;40%), lack species cross reactivity, and activate differing intracellular pathways than in mice. Thus, human model systems are essential for understanding the role of CRLF2 function in normal and malignant B lymphopoiesis. We have developed a novel human-only in vitro culture model that allows the study of human B cell development under highly selective cytokine stimulation. This model is based on co-culturing CD34+ hematopoietic stem cells (HSCs) with primary human bone marrow stroma supplemented with selective exogenous cytokines and/or specific cytokine neutralizing antibodies. We have previously used this model to show that IL-7 increases B cell progenitors by over 60 fold and that IL-7 is essential for normal human B cell production (J. Immunol. 2009 82:4255). Here we use our human-only in vitro model to examine the role of TSLP-induced signals in normal human B cell development. Our data show that TSLP induces an expansion of human B cell progenitor populations generated from HSCs in cord blood that is similar in magnitude to that observed for IL-7. A comparison of TSLP and IL-7 effects shows that TSLP targets early B cell progenitors (CD34+) inducing expansion of this population with limited differentiation. In contrast, IL-7 induces rapid differentiation to the CD34- stage followed by proliferation. RT-PCR and ELISA analysis show that normal human bone marrow stoma express both TSLP and IL-7, thus establishing an endogenous source of these cytokines at the site of normal and malignant hematopoiesis. Our data provide evidence that TSLP and IL-7 exert differential and stage specific effects on proliferation and differentiation of B cell progenitors and suggest that deregulation of the complex interplay between these signals in normal differentiation could set the stage for malignant transformation to B-ALL in the presence of cooperative defects in JAK2 and/or Ikaros. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1094. doi:10.1158/1538-7445.AM2011-1094

Accessibility control of TCR V region by STAT5

The signal of the IL-7R and signal transducers and activators of transcription (STAT) 5 plays an essential role in gammadelta T-cell development by inducing V-J recombination in the TCRgamma locus. Previously, we have shown that STAT5 binds to the Jgamma promoters and controls chromatin accessibility by histone acetylation. However, little is known on control mechanism of Vgamma region by the IL-7R. To elucidate the regulation by STAT5, we first analyzed the chromatin status of Vgamma region in primary thymocytes. The levels of histone H3 acetylation are high at Vgamma5, HsA element and Vgamma2 in Rag2(-/-) thymocytes but low in IL-7R alpha-chain (IL-7Ralpha)-deficient early thymocytes, suggesting that IL-7R signaling controls the accessibility of the Vgamma region. In addition, high levels of histone H3 acetylation and germ line transcription were induced at Vgamma5 and HsA by cytokine and STAT5 in cytokine-dependent Ba/F3 and other hematopoietic cell lines. Importantly, the chromatin accessibility of Vgamma5 gene is increased by cytokine signal. Furthermore, STAT5 was not recruited to a non-canonical STAT-binding motif in the endogenous chromatin of the Vgamma5 promoter by cytokine stimulation, while STAT5 binds to a consensus motif in the HsA element. In accordance with this result, STAT5 does not directly activate the Vgamma5 promoter by reporter assay. These results suggested that while STAT5 directly binds to HsA element and induces its histone acetylation, STAT5 indirectly activates the Vgamma5 promoter. Thus, this study implies a potential role of STAT5 in accessibility control of Vgamma region, especially at Vgamma5 and HsA.

RETRACTED: REDOX regulation of IL-13 signaling in intestinal epithelial cells: Usage of alternate pathways mediates distinct gene expression patterns

In the classic view interleukin-13 (IL-13) binds to a heterodimer protein complex of the IL-13Ralpha1 and IL-4Ralpha chains and signals through a Janus kinase 1 (JAK1)-signal transducer and activator of transcription 6 (STAT6) mechanism. We recently reported that IL-13 also signals through the IL-13Ralpha2 chain initiating all three mitogen activated protein kinase (MAPK) pathways, and the relative expression of IL-13Ralpha1 and IL-13Ralpha2 modulates one another's transduction pathway. Therefore we investigated whether generation of reactive oxygen species (ROS) as second messengers may serve as a common nexus between these two pathways emanating from the individual IL-13 receptor chains in intestinal epithelial cells (IEC). IL-13 stimulates intracellular ROS synthesis within 5min via IL-13Ralpha1-JAK1-STAT6- and IL-13Ralpha2-MEK1/2-ERK1/2-dependent activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-1 (NOX-1). IL-13-induced ROS generation in turn positively regulates phosphorylation of ERK1/2 and STAT6, yielding a feed forward amplification loop. IL-13 also stimulates the stable, long-term gene expression of two other NADPH oxidases, NOX-4 and DUOX-2, which along with constitutive NOX-1, might facilitate elevated, continuous production of ROS in IL-13-activated IEC. The contribution of each signal transduction pathway initiated by IL-13 engagement to such biological functions as wound healing, inflammation, and apoptosis was mapped for representative, responsive genes. Distinct usage patterns were observed, demonstrating not only that IL-13 signal transduction through STAT6, MAPK, and ROS is regulated in both an antagonistic and cyclic fashion, but also that each pathway plays a specific role in modulating the wound healing and anti-apoptotic capabilities of the intestinal epithelium.

Interleukin-2 Controls flt3L-dependent Development and Phenotype of Conventional and Plasmacytoid Dendritic Cells (36.19)

Abstract DC development requires the ligand for FMS-like tyrosine kinase 3 receptor (flt3L), but little is known regarding other cytokines that may control this process. In our study, we have addressed the effect of IL-2 on DC development. We have shown that the addition of IL-2 to flt3L-stimulated bone marrow (BM) cultures can block the development of both pDCs (CD11c+SiglecH+) and cDCs (CD11c+CD11b+), while expanding the populations of NK/NKT/T cells (CD3+/-NK1.l+/-). By sorting for DC precursors that are Lineage- flt3+ CD11c-, we confirm that IL-2 blocks DC development by acting directly on DC precursors, and not indirectly via its effect on NK/NKT/T cells. The inhibition of DC development by IL-2 is dependent on both the IL-2R alpha and beta chains, and STAT5. IL-2 treatment of DC precursors leads to a decrease in the expression of various transcription factors crucial for DC development. In addition, our ongoing studies indicate that the presence of IL-2 during flt3L-dependent DC development also alters the phenotype of DCs. Together our data has indicated that IL-2 inhibits the development of DCs, and suggests IL-2 can also alter DC phenotype. This has important implications in the therapeutic use of IL-2, as well as our current understanding on factors that can lead to the loss of immune tolerance in various autoimmune diseases.

The role of IL-6 in T-bet (-/-) mice in an allergic asthma model (91.10)

Abstract IL-6 is a pleiotropic cytokine which induces Th2 type cells. IL-6 binds to IL-6R alpha chain and then induces gp130 dimerization resulting in the intracellular activation of Janus kinase and signal transducers and activators of transcription (STAT) pathways. We previously demonstrated that patients affected by allergic asthma have an increased level of soluble IL-6R which correlates with Th2 CD4+ T-cells in their airways. In a murine model of this disease, we also demonstrated that IL-6 inhibits the development of T-regulatory cells (Tregs) and local blockade of IL-6R resulted in the expansion of Tregs as well as Th1 cells in the lung. T-bet is a Th1-specific transcriptional factor. Mice lacking T-bet show increased asthmatic symptoms. We thus want to study the influence of T-bet on IL-6 mediated inhibition of Tregs. To this aim an antibody against IL-6R was applied to T-bet deficient mice (T-bet (-/-)) during allergen challenge. In preliminary studies we found that local blockade of IL-6R in T-bet (-/-) mice resulted in a reduced AHR and decreased lung eosinophilia. Furthermore we observed selective expansion of the CD4+ CD25+ Foxp3+ Tregs in the draining lymph-nodes taken from anti IL-6R-antibody treated T-bet (-/-) mice, compared to T-bet (-/-) untreated mice. These results suggest that local blockade of IL-6R in the absence of T-bet in allergic asthma could result in amelioration of the disease hallmarks because of inducing Tregs in the local draining lymph nodes.

Upregulation of interleukin-13 receptor chains in bronchial smooth muscle tissues of mouse experimental asthma

Interleukin-13 (IL-13) is believed to be a central mediator of the induction of airway hyperresponsiveness (AHR), one of the characteristic features of allergic bronchial asthma. The IL-13-mediated events are mainly generated by its binding to functional IL-13 receptor, IL13Ralpha1 chain. In the present study, the changes in the levels of IL-13 receptors in bronchial smooth muscles were determined in mice with AHR induced by antigen inhalation. Mice were sensitized and repeatedly challenged with ovalbumin antigen. Total RNAs of the left main bronchi were extracted, and real-time RT-PCR analyses for IL13Ralpha1 and IL13Ralpha2 chains were conducted. As a result, both the receptor chains were significantly increased in the diseased bronchial smooth muscle. The time-course analyses revealed that the peaks of IL13Ralpha1 and IL13Ralpha2 upregulations were at 6 hour and 3-12 hour after the last antigen inhalation, respectively. It is thus possible that the IL-13-mediated signaling in bronchial smooth muscle is considerably augmented by the upregulations of IL-13 itself and its functional IL13Ralpha1 receptor in allergic asthmatics.

Thymic Stromal Lymphopoietin Induces Chemotactic and Prosurvival Effects in Eosinophils

Thymic stromal lymphopoietin (TSLP) is highly expressed by bronchial epithelial cells and skin keratinocytes in allergic diseases. TSLP acts as a master switch for allergic inflammation through the activation of dendritic cells and mast cells for initiating inflammatory type 2 T-helper lymphocyte responses. To elucidate the immunological cascades of epithelium/keratinocyte-eosinophil-mediated allergic inflammation, we examined the modulating effects of TSLP on human eosinophils. Expression of TSLP receptor complex was detected by RT-PCR, flow cytometry, and Western blot. Adhesion molecules, cytokine, and chemokines were quantitated by flow cytometry or ELISA. Intracellular signal transduction molecules were measured by Western blot and flow cytometry. We observed that human eosinophils constitutively expressed functional heterodimeric TSLP receptor complex comprising TSLP-binding chain TSLPR and IL-7Ralpha chain. TSLP could significantly delay eosinophil apoptosis, up-regulate cell surface expression of adhesion molecule CD18 and intercellular adhesion molecule-1, but down-regulate L-selectin, enhance eosinophil adhesion onto fibronectin, and induce the release of inflammatory cytokine IL-6 and chemokines CXCL8, CXCL1, and CCL2 (all P < 0.05). All these effects were concentration dependent and TSLP specific. TSLP regulated the above effects through the activation of extracellular signal-regulated protein kinase, p38 mitogen-activated protein kinase, and NF-kappaB signaling pathway, but not signal transducer and activator of transcription 5 and 3, which were usually activated in other effector cells upon TSLP stimulation. Collectively, the above findings elucidate the proallergic mechanisms of TSLP via the activation of distinct intracellular signaling pathways in eosinophils.

Early production of thymic stromal lymphopoietin precedes infiltration of dendritic cells expressing its receptor in allergen‐induced late phase cutaneous responses in atopic subjects

Thymic stromal lymphopoietin (TSLP) is an interleukin (IL)-7-like cytokine that triggers dendritic cell-mediated T helper (Th)2 inflammatory responses through a receptor consisting of a heterodimer of the IL-7 receptor alpha (IL-7Ralpha) chain and the TSLP receptor (TSLPR), which resembles the cytokine receptor common gamma chain. Dendritic cells activated by TSLP prime development of CD4(+) T cells into Th2 cells contributing to the pathogenesis of allergic inflammation. We hypothesized that allergen exposure induces expression of TSLP and results in recruitment of TSLPR bearing cells in the cutaneous allergen-induced late-phase reaction (LPR) in atopic subjects. Skin biopsies were obtained from atopic subjects (n = 9) at various times after cutaneous allergen challenge. In situ hybridization and immunohistochemistry were used to determine TSLP mRNA expression and to measure infiltration of TSLPR(+) DC in skin LPR. RT-PCR and flow cytometry were employed to analyse TSLPR expression on isolated blood DC. Allergen-induced skin TSLP expression occurred as early as 1 h after allergen challenge, whereas TSLPR(+) and CD11c(+) cells infiltrated relatively late (24-48 h). The majority of TSLPR(+) cells were DC co-expressing blood DC antigen-1 (BDCA-1) or BDCA-2. Freshly isolated blood DC expressed both TSLPR and IL-7Ralpha chains. Maturation and stimulation with TSLP or polyriboinosinic-polyribocytidylic acid in vitro upregulated the expression of both TSLPR and IL-7Ralpha chains in DC but not in chemoattractant receptor-homologous molecule expressed on Th2 cells(+) CD4(+) T cells. The data suggest that TSLP plays a role in augmenting, through DC recruitment and activation, the development of Th2-type T cells in allergic inflammation.

Role of IL-4 and Th2 responses in allograft rejection and tolerance

Due to the dominance of Th1 cytokines in rejection and the ability of Th2 cytokines, particularly IL-4, to inhibit Th1 responses, it has long been held that Th2 cytokines can improve transplant outcomes. Although there is some support for this, there is mounting evidence that IL-4 and Th2 cytokines can promote graft dysfunction. These disparate effects are reviewed. The role of Th2 cytokines in graft dysfunction is not necessarily due to promotion of humoral immunity, but is due to their ability to drive T-cell and non-T-cell responses including alternative activation of macrophages. Alternatively, activated macrophages compete with classically activated macrophages for arginine and they are mutually exclusive, analogous to mutual competition between Th1 and Th2 cells. Recent findings also point to two subsets of regulatory T cells (Tregs), each dependent on either Th1 or Th2 cytokines. In addition to its effects on bone marrow-derived cells, IL-4 affects parenchymal cells by signalling through the type II receptor, which consists of the IL-4R alpha chain (IL-4Ralpha) and the IL-13Ralpha1, which also binds IL-13. The effects of Th2 cytokines in transplantation depend on their cellular targets, the timing and form of administration and on Th2 cytokine-dependent Tregs.

Opposite roles of STAT and PPARgamma in the induction of p21WAF1 expression by IL-13 in human peripheral blood monocytes.

The cyclin kinase inhibitor p21WAF1 is expressed in most, if not all, differentiated cells in the human body and represents an important regulator of cell cycle control and terminal differentiation in the monocyte/macrophage lineage. It has been reported in macrophage cell lines that p21WAF1 expression is sensitive to numerous molecules including cytokines, but nothing was known about p21WAF1 regulation in human peripheral blood monocytes in response to Th2 cytokines. We report here, that IL-13 increases p21WAF1 expression in human blood monocytes. This induction is a transcription-dependent event, leading to an increase in mRNA content. We show that the signalling pathway for IL-13-induced p21WAF1 expression may involve the IL-4R alpha and the IL-13R alpha1 chains, and the tyrosine and JAK2 kinases. Also, p21WAF1 plasmid-based gene activation only requires a minimal p21WAF1 promoter, containing a putative PPRE. Since IL-13 signalisation involves PPARgamma, we tested PPARgamma involvement in p21WAF1 gene activation by using metabolic inhibitors of arachidonic acid metabolism, or by restoring PPARgamma expression in a defective cell line. We found that inhibition of PPARgamma increases IL-13-induced p21WAF1 gene expression in these models. These data argue that IL-13 upregulates p21WAF1 expression in monocytes via JAK/STAT pathway, and that the activation of PPARgamma by this cytokine can counteract this induction.