Γc Cytokine Receptor Research Articles

Blocking common γ chain cytokine signaling ameliorates T cell-mediated pathogenesis in disease models.

The common γ chain (γc; IL-2RG) is a subunit of the interleukin (IL) receptors for the γc cytokines IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21. The lack of appropriate neutralizing antibodies recognizing IL-2RG has made it difficult to thoroughly interrogate the role of γc cytokines in inflammatory and autoimmune disease settings. Here, we generated a γc cytokine receptor antibody, REGN7257, to determine whether γc cytokines might be targeted for T cell-mediated disease prevention and treatment. Biochemical, structural, and in vitro analysis showed that REGN7257 binds with high affinity to IL-2RG and potently blocks signaling of all γc cytokines. In nonhuman primates, REGN7257 efficiently suppressed T cells without affecting granulocytes, platelets, or red blood cells. Using REGN7257, we showed that γc cytokines drive T cell-mediated disease in mouse models of graft-versus-host disease (GVHD) and multiple sclerosis by affecting multiple aspects of the pathogenic response. We found that our xenogeneic GVHD mouse model recapitulates hallmarks of acute and chronic GVHD, with T cell expansion/infiltration into tissues and liver fibrosis, as well as hallmarks of immune aplastic anemia, with bone marrow aplasia and peripheral cytopenia. Our findings indicate that γc cytokines contribute to GVHD and aplastic anemia pathology by promoting these characteristic features. By demonstrating that broad inhibition of γc cytokine signaling with REGN7257 protects from immune-mediated disorders, our data provide evidence of γc cytokines as key drivers of pathogenic T cell responses, offering a potential strategy for the management of T cell-mediated diseases.

Which is the Ideal JAK Inhibitor for Alopecia Areata - Baricitinib, Tofacitinib, Ritlecitinib or Ifidancitinib - Revisiting the Immunomechanisms of the JAK Pathway.

Alopecia areata (AA) is an immune-mediated condition, clinically manifesting as non-cicatricial patches of alopecia. It is often a self-limiting condition; however, regrowth of hair can take a long period of time, resulting in significant psychological comorbidity. With the recent advances in pathomechanisms of AA, the therapeutic approach to the condition has become more specific, and targeted therapy with small molecules is probably the ideal intervention. Many therapies exist for AA, but none of the systemic agents were approved, until recently, when baricitinib (Janus kinase (JAK1 and JAK2 inhibitor) gained FDA approval for the treatment of adult patients with severe AA. JAK inhibitors (JAKibs) target the γc cytokine and interferon-gamma (IFN-γ) signaling pathway, which is critical to the immunopathogenesis of AA and thus can reverse the hair loss in AA. Although JAKibs are emerging as a promising treatment modality for AA, the ideal JAKib is not yet settled, as there is scant data on H-2-H (head-to-head) comparisons of JAK inhibitors in AA. Moreover, the response achieved with JAKibs is not sustained after treatment discontinuation, with many studies showing a high recurrence rate with tofacitinib and ruxolitinib post-treatment. Also, recent studies have hypothesized that JAK2, with its ubiquitous expression, can cause adverse effects, unlike JAK1, which is associated with multiple major cytokine receptor families and JAK3, which is exclusively associated with the γc cytokine receptor. Thus, JAK3ibs may be associated with a better side effect profile and, in conjunction with their specificity, may replace other JAKibs as the treatment of choice for AA. We herein discuss the role of the JAK/STAT (signal transducer and activator of transcription) pathway in AA, the intricacies of various JAKibs in the management of AA, and emphasize the need for studies on tissue JAK and cytokine expression before arriving at the ideal JAKibs for AA.

Remote control of γc expression by arginine methylation.

Arginine methylation is a post-translational modification that controls the abundance of γc cytokine receptor on mature T cells by a post-transcriptional mechanism.

Soluble γc cytokine receptor suppresses IL-15 signaling and impairs iNKT cell development in the thymus.

The soluble γc protein (sγc) is a naturally occurring splice isoform of the γc cytokine receptor that is produced by activated T cells and inhibits γc cytokine signaling. Here we show that sγc expression is also highly upregulated in immature CD4+CD8+ thymocytes but then downregulated in mature thymocytes. These results indicate a developmentally controlled mechanism for sγc expression and suggest a potential role for sγc in regulating T cell development in the thymus. Indeed, sγc overexpression resulted in significantly reduced thymocyte numbers and diminished expansion of immature thymocytes, concordant to its role in suppressing signaling by IL-7, a critical γc cytokine in early thymopoiesis. Notably, sγc overexpression also impaired generation of iNKT cells, resulting in reduced iNKT cell percentages and numbers in the thymus. iNKT cell development requires IL-15, and we found that sγc interfered with IL-15 signaling to suppress iNKT cell generation in the thymus. Thus, sγc represents a new mechanism to control cytokine availability during T cell development that constrains mature T cell production and specifically iNKT cell generation in the thymus.

The role of soluble common gamma chain in autoimmune disease.

The common gamma chain (γc) is the central signaling unit for a number of cytokine receptors collectively known as the γc cytokine receptor family. γc is critical for ligand binding and signaling by γc cytokines. γc cytokine signaling had been thought to be mainly regulated by cytokine-specific receptor α chain expression levels with little or no effect by γc surface levels because γc expression was presumed to remain unchanged during T-cell activation and development. The extent of γc cytokine responses is thought to be regulated by cytokine specific receptor subunits and not by the γc receptor. In contrast to this prevailing view, we have recently reported that γc itself actively regulates γc cytokine responses. Interestingly, γc exerted its regulatory effects not only as a conventional membrane receptor protein but also as a secreted protein whose expression was upregulated upon T-cell stimulation. Here we will review how a soluble form of γc, which is generated by alternative splicing, regulates γc cytokine signaling and plays a role in controlling immune activation related to autoimmune disease.

The advent of soluble common gamma chain rocks the T cell world; A novel therapeutic target for autoimmune diseases

The common gamma chain (γc) is the central signaling unit for the γc cytokine receptor family. γc cytokine signaling is mainly regulated by cytokine-specific receptor alpha chain expression levels but not γc expression levels. Here we will highlight that a soluble form of γc (sγc) expression, which is generated by alternative splicing, impairs naive T cell survival and promotes inflammation in a manner of inhibiting IL-7 and IL-2 signaling, representatively. Furthermore, sγc expression is significantly enhanced upon T cell activation. sγc enhances in vitro and in vivo Th17 differentiation through dampening of IL-2 signal, and sγc-overexpressing mice are consequently more susceptible to EAE. Therefore, sγc is a novel immunoregulator that control T cell biology by regulation of γc cytokine signaling.

Pim1 permits generation and survival of CD4+T cells in the absence of γc cytokine receptor signaling

γ-Chain (γc) cytokine receptor signaling is required for the development of all lymphocytes. Why γc signaling plays such an essential role is not fully understood, but induction of the serine/threonine kinase Pim1 is considered a major downstream event of γc as Pim1 prevents apoptosis and increases metabolic activity. Consequently, we asked whether Pim1 overexpression would suffice to restore lymphocyte development in γc-deficient mice. By analyzing Pim1-transgenic γc-deficient mice (Pim1(Tg) γc(KO) ), we show that Pim1 promoted T-cell development and survival in the absence of γc. Interestingly, such effects were largely limited to CD4(+) lineage αβ T cells as CD4(+) T-cell numbers improved to near normal levels but CD8(+) T cells remained severely lymphopenic. Notably, Pim1 over-expression failed to promote development and survival of any T-lineage cells other than αβ T cells, as we observed complete lack of γδ, NKT, FoxP3(+) T regulatory cells and TCR-β(+) CD8αα IELs in Pim1(Tg) γc(KO) mice. Collectively, these results uncover distinct requirements for γc signaling between CD4(+) αβ T cells and all other T-lineage cells, and they identify Pim1 as a novel effector molecule sufficient to drive CD4(+) αβ T-cell development and survival in the absence of γc cytokine receptor signaling.

Chimeric γc cytokine receptors confer cytokine independent engraftment of human T lymphocytes

Therapeutic responses following adoptive transfer of T cells correlate to levels of long-term T cell persistence. Lymphodepletion and exogenous γc cytokine administration can improve T cell persistence following adoptive transfer, but their effects are not uniform and toxicities are significant. To overcome these limitations, we designed a chimeric γc cytokine receptor (CγCR) composed of Interleukin-7 (IL-7) tethered to IL-7Rα/CD127 that confers exogenous cytokine independent, cell intrinsic, STAT5 cytokine signals. We additionally show that this design is modular in that the IL-2Rβ/CD122 cytoplasmic chain can be exchanged for that of IL-7Rα/CD127, enhancing Shc activity. When expressed in central memory-derived primary human CD8+ CTL (TE/CM), these CγCRs signal according to their corresponding wild-type counterparts to support exogenous cytokine independent viability and homeostatic proliferation, while retaining full effector function. In vivo studies demonstrate that both CγCR-CD127+ and CγCR-CD122+ CD8+ TE/CM engraft in mice and persist in an absence of exogenous cytokine administration. Engrafted CγCR-CD127+ CD8+ TE/CM preferentially retain central memory marker expression in vivo demonstrating a dichotomy between CD127 versus CD122 signaling. Together, these results suggest that expression of CγCR in therapeutic T cells may aid in the in vivo persistence of these cells, particularly under conditions of limiting homeostatic cytokines.

Human Papillomaviruses Associated with Epidermodysplasia Verruciformis in Non-Melanoma Skin Cancers: Guilty or Innocent?

Abbreviations: AK, actinic keratoses; EV, epidermodysplasia verruciformis; HPV, human papillomavirus; ISH, in situ hybridization; NMSC, non-melanoma skin cancers; OTR, organ transplant recipients; SCC, squamous cell carcinomas; UVR, ultraviolet radiation

Cortactin and dynamin are required for the clathrin-independent endocytosis of gammac cytokine receptor.

Endocytosis is critical for many cellular functions. We show that endocytosis of the common γc cytokine receptor is clathrin independent by using a dominant-negative mutant of Eps15 or RNA interference to knock down clathrin heavy chain. This pathway is synaptojanin independent and requires the GTPase dynamin. In addition, this process requires actin polymerization. To further characterize the function of dynamin in clathrin-independent endocytosis, in particular its connection with the actin cytoskeleton, we focused on dynamin-binding proteins that interact with F-actin. We compared the involvement of these proteins in the clathrin-dependent and -independent pathways. Thus, we observed that intersectin, syndapin, and mAbp1, which are necessary for the uptake of transferrin (Tf), a marker of the clathrin route, are not required for γc receptor endocytosis. Strikingly, cortactin is needed for both γc and Tf internalizations. These results reveal the ubiquitous action of cortactin in internalization processes and suggest its role as a linker between actin dynamics and clathrin-dependent and -independent endocytosis.

Severe cutaneous papillomavirus disease after haemopoietic stem-cell transplantation in patients with severe combined immune deficiency caused by common γc cytokine receptor subunit or JAK-3 deficiency

Haemopoietic stem-cell transplantation is a life-saving treatment for severe combined immune deficiency. However, there has been little long-term follow-up of this treatment. There is evidence for the persistance of partial immunodeficiency associated with significant infections, including severe human papillomavirus (HPV) disease. We did a retrospective analysis of severe HPV disease in a group of 41 patients with severe combined immune deficiency from one centre who were alive 10 years or longer after haemopoietic stem-cell transplantation. Nine of the 41 patients had extensive chronic HPV disease limited to the skin, with a median onset at 8 years after transplantation. Four had lesions typical of epidermodysplasia verruciformis, a rare genodermatosis. Transplant characteristics, immune status, and chimerism of these nine patients did not differ significantly from those of the other patients. The nine patients with HPV disease had severe combined immune deficiency associated with either common gammac receptor cytokine subunit or Janus kinase-3 (JAK-3) deficiency. By contrast, patients with other forms of severe combined immune deficiency did not have any signs of HPV disease. That genetic causes are the only predisposing factor to be identified for severe combined immune deficiency, suggests that natural-killer cells or gammac/JAK-3-dependent signalling in keratinocytes could have a role in anti-HPV immunity.

Gene therapy in haematology and oncology

Katherine A High is a professor of paediatrics at the University of Pennsylvania, and Director of Research in the Hematology Division of the Children's Hospital of Philadelphia. She is a member of the Scientific Advisory board of Avingen Inc—a company in which she holds equity. “There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy…” William Shakespeare, Hamlet Gene therapy is a novel area of therapeutics in which the active agent is a nucleic-acid sequence rather than a protein or small molecule. The possibilities for gene therapy are enormous. The approach could be used to supply a normal copy of a missing or defective gene in genetic diseases; to improve the safety or efficacy of other drugs; or to restore normal physiology in the setting of acquired disease. These possibilities have been limited, however, by the practical difficulties that have attended efforts to achieve efficient gene transfer and gene expression for an appropriate duration, and much of the first decade of clinical gene therapy has been characterised by disappointments arising from inefficient gene transfer, only transient gene expression, or both. As technology related to gene-delivery vehicles has evolved, clinical results have moved closer to the desired outcome. A gene-therapy approach to treatment of any disease requires three elements: a therapeutic gene to be transferred; a vector to effect the transfer; and appropriately chosen target cells in the recipient. In genetic diseases, the identity of the therapeutic gene is generally not in question, and the first convincing successes have come in these disorders. Clinical gene therapy began with the introduction via a retroviral vector of the gene encoding adenosine deaminase into the lymphocytes of two young patients with severe combined immunodeficiency disease (SCID). Although the treatment had limited success, and the efficiency of gene transfer was quite low, this attempt helped to define the technical limitations of the approach and to establish areas for research. Several conceptual and technical advances have facilitated the successful application of this approach, in which haemopoietic cells are removed from the patient, transduced with the vector bearing the donated gene, and then reinfused: the development of reliable techniques for isolating CD34-positive cells; the characterisation of cytokines that can promote proliferation (required for retroviral transduction) of haemopoietic cells without compromising their reconstitution capacity; the ability to concentrate vector to achieve high-titre preparations; and the definition of optimum conditions for direct contact between the retroviral particle and the target. All these advances contributed to the successful treatment of children with X-linked SCID. This disorder is due to a mutation in the gene encoding the γc cytokine receptor subunit of the receptors for various interleukins that are critical for the growth and differentiation of lymphoid cells. The investigators used a retroviral vector expressing γc, transduced CD34-positive cells from affected children, and found after reinfusion of the transduced cells reconstitution of T, B, and natural killer cells, that continued for over a year. In haemophilia B, adeno-associated viral vectors expressing human factor IX have been introduced into skeletal muscle, and successful gene transfer and expression have been shown on muscle biopsy. Further dose-escalation studies are needed to identify a safe dose at which all patients have a demonstrable therapeutic effect. A plasmid-based approach for treatment of haemophilia A has also shown promise in early-phase clinical testing. In cancer therapy, a modified adenoviral vector that replicates specifically in cells lacking functional p53 has been shown in large trials to induce tumour-specific lysis in head and neck tumours. Moreover, this gene-based approach is synergistic with conventional chemotherapy and radiotherapy. An unresolved question is whether the vector alone would have similar therapeutic effects related to the immune response. One of the lessons of this first decade of clinical gene therapy is the importance of focusing on diseases that can be targeted with the available technology. Thus, in the case of X-linked SCID, the transduced cells have a marked proliferative advantage in vivo compared to untransduced cells and, therefore, engraftment is possible even without prior myeloablation. Continued improvements in gene delivery systems will allow the extension of gene therapy approaches to an ever-increasing range of human diseases. Proof-of-concept studies in animal models have already been completed for retinitis pigmentosa and for lysosomal storage disease, disorders for which there is currently no treatment. Recombinant proteins once appeared far too complex and difficult to standardise, yet they are now a standard part of the therapeutic armamentarium. Similarly, vehicles of gene delivery, whether viral or non-viral, represent a new level of complexity in therapeutics, but recent data suggest that these too can be successfully developed for treatment of human disease.