Tyrosine phosphorylation and activation of STAT5, STAT3, and Janus kinases by interleukins 2 and 15

Greater mechanistic understanding of the cutaneous pathogenesis of Stevens-Johnson syndrome/toxic epidermal necrolysis can shed light on novel therapeutic strategies: a comprehensive review

PURPOSE OF REVIEW

Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) are severe cutaneous adverse drug reactions (SCARs) characterized by widespread epithelial detachment and blistering, which affects the skin and mucocutaneous membranes. To date, therapeutic interventions for SJS/TEN have focused on systematic suppression of the inflammatory response using high-dose corticosteroids or intravenous immunoglobulin G (IgG), for example. No targeted therapies for SJS/TEN currently exist.

RECENT FINDINGS

Though our understanding of the pathogenesis of SJS/TEN has advanced from both an immunological and dermatological perspective, this knowledge is yet to translate into the development of new targeted therapies.

SUMMARY

Greater mechanistic insight into SJS/TEN would potentially unlock new opportunities for identifying or repurposing targeted therapies to limit or even prevent epidermal injury and blistering.

STAT5 Is Necessary for the Metabolic Switch Induced by IL-2 in Cervical Cancer Cell Line SiHa

The tumor cells reprogram their metabolism to cover their high bioenergetic demands for maintaining uncontrolled growth. This response can be mediated by cytokines such as IL-2, which binds to its receptor and activates the JAK/STAT pathway. Some reports show a correlation between the JAK/STAT pathway and cellular metabolism, since the constitutive activation of STAT proteins promotes glycolysis through the transcriptional activation of genes related to energetic metabolism. However, the role of STAT proteins in the metabolic switch induced by cytokines in cervical cancer remains poorly understood. In this study, we analyzed the effect of IL-2 on the metabolic switch and the role of STAT5 in this response. Our results show that IL-2 induces cervical cancer cell proliferation and the tyrosine phosphorylation of STAT5. Also, it induces an increase in lactate secretion and the ratio of NAD+/NADH, which suggest a metabolic reprogramming of their metabolism. When STAT5 was silenced, the lactate secretion and the NAD+/NADH ratio decreased. Also, the expression of HIF1α and GLUT1 decreased. These results indicate that STAT5 regulates IL-2-induced cell proliferation and the metabolic shift to aerobic glycolysis by regulating genes related to energy metabolism. Our results suggest that STAT proteins modulate the metabolic switch in cervical cancer cells to attend to their high demand of energy required for cell growth and proliferation.

Hippo kinases Mst1 and Mst2 maintain NK cell homeostasis by orchestrating metabolic state and transcriptional activity

Natural killer (NK) cells play a crucial role in immune response against viral infections and tumors. However, further investigation is needed to better understand the key molecules responsible for determining the fate and function of NK cells. In this study, we made an important discovery regarding the involvement of the Hippo kinases Mst1 and Mst2 as novel regulators in maintaining mouse NK cell homeostasis. The presence of high Mst1 and Mst2 (Mst1/2) activity in NK cells is essential for their proper development, survival and function in a canonical Hippo signaling independent mode. Mechanistically, Mst1/2 induce cellular quiescence by regulating the processes of proliferation and mitochondrial metabolism, thereby ensuring the development and survival of NK cells. Furthermore, Mst1/2 effectively sense IL-15 signaling and facilitate the activation of pSTAT3-TCF1, which contributes to NK cell homeostasis. Overall, our investigation highlights the crucial role of Mst1/2 as key regulators in metabolic reprogramming and transcriptional regulation for mouse NK cell survival and function, emphasizing the significance of cellular quiescence during NK cell development and functional maturation.

Omenn Syndrome in Two Infants with Different Hypomorphic Variants in Janus Kinase 3

Biallelic null or hypomorphic variants in JAK3 cause SCID and less frequently Omenn syndrome. We investigated homozygous hypomorphic JAK3 mutations in two patients, and expression and function of a novel JAK3R431P variant in Omenn syndrome. Immunophenotyping of PBMC from the patient with the novel JAK3R431P variant was undertaken, by flow cytometry and Phosflow after stimulation with IL-2, IL-7, and IL-15. JAK3 expression was investigated by Western blotting. We report two patients with homozygous hypomorphic JAK3 variants and clinical features of Omenn syndrome. One patient had a previously described JAK3R775H variant, and the second had a novel JAK3R431P variant. One patient with a novel JAK3R431P variant had normal expression of JAK3 in immortalised EBV-LCL cells but reduced phosphorylation of STAT5 after stimulation with IL-2, IL-7, and IL-15 consistent with impaired kinase activity. These results suggest the JAK3R431P variant to be hypomorphic. Both patients are alive and well after allogeneic haematopoietic stem cell transplantation. They have full donor chimerism, restitution of thymopoiesis and development of appropriate antibody responses following vaccination. We expand the phenotype of hypomorphic JAK3 deficiency and demonstrate the importance of functional testing of novel variants in disease-causing genes.

Signalling mechanisms driving homeostatic and inflammatory effects of interleukin-15 on tissue lymphocytes

There is an intriguing dichotomy in the function of cytokine interleukin-15-at low levels, it is required for the homeostasis of the immune system, yet when it is upregulated in response to pathogenic infections or in autoimmunity, IL-15 drives inflammation. IL-15 associates with the IL-15Rα within both myeloid and non-haematopoietic cells, where IL-15Rα trans-presents IL-15 in a membrane-bound form to neighboring cells. Alongside homeostatic maintenance of select lymphocyte populations such as NK cells and tissue-resident T cells, when upregulated, IL-15 also promotes inflammatory outcomes by driving effector function and cytotoxicity in NK cells and T cells. As chronic over-expression of IL-15 can lead to autoimmunity, IL-15 expression is tightly regulated. Thus, blocking dysregulated IL-15 and its downstream signalling pathways are avenues for immunotherapy. In this review we discuss the molecular pathways involved in IL-15 signalling and how these pathways contribute to both homeostatic and inflammatory functions in IL-15-dependent mature lymphoid populations, focusing on innate, and innate-like lymphocytes in tissues.

Bone marrow monocytes sustain NK cell-poiesis during non-alcoholic steatohepatitis

Natural killer (NK) cells are the predominant lymphocyte population in the liver. At the onset of non-alcoholic steatohepatitis (NASH), an accumulation of activated NK cells is observed in the liver in parallel with inflammatory monocyte recruitment and an increased systemic inflammation. Using in vivo and in vitro experiments, we unveil a specific stimulation of NK cell-poiesis during NASH by medullary monocytes that trans-present interleukin-15 (IL-15) and secrete osteopontin, a biomarker for patients with NASH. This cellular dialogue leads to increased survival and maturation of NK precursors that are recruited to the liver, where they dampen the inflammatory monocyte infiltration. The increase in the production of both osteopontin and the IL-15/IL-15Rα complex by bone marrow monocytes is induced by endotoxemia. We propose a tripartite gut-liver-bone marrow axis regulating the immune population dynamics and effector functions during liver inflammation.

Efficacy of using oral methotrexate with phototherapy in the treatment of vitiligo in comparison with single phototherapy treatment: A double-blinded randomized controlled trial

BACKGROUND

Vitiligo is an acquired skin disease with a worldwide prevalence of 0.5%-2% and a tendency to involve both genders. Although the exact pathologic mechanism is unknown, there is some evidence for the role of autoimmunity in this disease. Based on this theory, various immunosuppressive agents, such as topical or systemic corticosteroids and phototherapy (including narrowband ultraviolet B), are used. Methotrexate is another immunosuppressant that has recently become popular as a single treatment for vitiligo; however, the synergistic effect and its superiority over other treatments are two crucial factors that are still obscure. This study aimed to compare the efficacy of methotrexate+ NB-UVB versus placebo+ NB-UVB in vitiligo patients.

METHODS

In this double-blinded, randomized controlled trial, 42 patients were randomly allocated into two groups: the first group received three times weekly NB-UVB plus placebo, and the second group was treated with three times weekly NB-UVB in combination with a weekly dose of 12.5 mg MTX. The total duration of treatment was 6 months, patients were followed up every 2 months, and the assessment tools were VASI (repigmentation indicator) and VIDA (disease activity indicator) scores.

RESULTS

Both treatment groups showed improvement in VASI and VIDA scores during 6-month follow-up, but no statistical significance was found between the two treatment methods.

CONCLUSION

This study demonstrated that both treatment modalities were equally effective, and further studies are required to evaluate the efficacy of MTX with other medications with longer follow-up and a larger sample size.

Blocking of oestrogen signals improves anti-tumour effect regardless of oestrogen receptor alpha expression in cancer cells

BACKGROUND

Anti-oestrogenic therapy has been used for breast cancer patients with oestrogen susceptibility cancer cells. However, little has been known about its potential role for immune cell biology within TME, particularly in cancer patients without oestrogen sensitivity of tumour cells. Therefore, we aimed to study the effect of oestrogen on immunity within TME.

METHODS

Using a clinical dataset, immune cells of humans and mice, female mice with and without ovaries, and several murine ERα-negative cancer cell lines, we evaluated the effect of oestrogen on immunity in TME.

RESULTS

Clinical data analysis suggested oestrogen's suppressive efficacy against CTLs. Additionally, in vitro and in vivo experiments revealed intra-tumoural CTLs' direct repressive action by oestrogen in both mice and humans; blockade of oestrogen signals cancelled its immunosuppression resulting in tumour growth reduction in vivo. Most notably, immunotherapy (immune checkpoint inhibitor; ICI) combined with anti-oestrogenic therapy exhibited a dramatic anti-tumour effect.

CONCLUSIONS

This study provides novel insights into how oestrogen contributes to tumour progression and a therapeutic rationale for blocking oestrogen signalling to boost the anti-tumour effect of ICI, regardless of tumour cells' ERα expression.

IL-2-induced Stat3 Signaling is Critical for Effector Treg Cell Programming

Maintenance of immune homeostasis to the intestinal mictrobiota is dependent on a population of effector regulatory T (eTreg) cells that develop from microbiota-reactive induced (i)Treg cells. A cardinal feature of eTreg cells is their production of IL-10, which plays a non-redundant role in immune tolerance of commensal microbes. Here, we identify an unexpected role for IL-2-induced Stat3 signaling to program iTreg cells for eTreg cell differentiation and Il10 transcriptional competency. IL-2 proved to be both necessary and sufficient for eTreg cell development - contingent on Stat3 output of the IL-2 receptor coordinate with IL-2 signaling during early Treg cell commitment. Induction of iTreg cell programming in absence of IL-2-induced Stat3 signaling resulted in impaired eTreg cell differentiation and a failure to produce IL-10. An IL-2 mutein with reduced affinity for the IL-2Rγ (γ c ) chain was found to have blunted IL-2R Stat3 output, resulting in a deficiency of Il10 transcriptional programming that could not be fully rescued by Stat3 signaling subsequent to an initial window of iTreg cell differentiation. These findings expose a heretofore unappreciated role of IL-2 signaling that acts early to program subsequent production of IL-10 by developing eTreg cells, with broad implications for IL-2-based therapeutic interventions in immune-mediated diseases.

Reigniting hope in cancer treatment: the promise and pitfalls of IL-2 and IL-2R targeting strategies

Interleukin-2 (IL-2) and its receptor (IL-2R) are essential in orchestrating immune responses. Their function and expression in the tumor microenvironment make them attractive targets for immunotherapy, leading to the development of IL-2/IL-2R-targeted therapeutic strategies. However, the dynamic interplay between IL-2/IL-2R and various immune cells and their dual roles in promoting immune activation and tolerance presents a complex landscape for clinical exploitation. This review discusses the pivotal roles of IL-2 and IL-2R in tumorigenesis, shedding light on their potential as diagnostic and prognostic markers and their therapeutic manipulation in cancer. It underlines the necessity to balance the anti-tumor activity with regulatory T-cell expansion and evaluates strategies such as dose optimization and selective targeting for enhanced therapeutic effectiveness. The article explores recent advancements in the field, including developing genetically engineered IL-2 variants, combining IL-2/IL-2R-targeted therapies with other cancer treatments, and the potential benefits of a multidimensional approach integrating molecular profiling, immunological analyses, and clinical data. The review concludes that a deeper understanding of IL-2/IL-2R interactions within the tumor microenvironment is crucial for realizing the full potential of IL-2-based therapies, heralding the promise of improved outcomes for cancer patients.

Interleukin-2 family cytokines: An overview of genes, expression, signaling and functional roles in teleost

The interleukin-2 (IL-2) family cytokines include IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21, which share γ chain (γc) subunit in receptors. The IL-2 family cytokines have unique biological effects that regulate differentiation, survival and activation of multiple lymphocyte lineages. Deficiency of IL-2 family signaling pathway in mammals prevents CD4⁺ T cells from developing effector functions and CD8⁺ T cells from developing immunological memory. In the present review, we addressed available information from teleost IL-2 family cytokines and discussed implications in teleost immunity. Also, we described and discussed their expression profiles, receptors, signaling transductions and functions. In teleost, IL-2 family has 5 members (IL-2, IL-4/13, IL-7, IL-15, IL-21) without IL-9, and their receptors share a common γc subunit and include other 6 subunits (IL-2Rβ1/2, IL-4Rα1/2, IL-13Rα1/2, IL-7Rα, IL-15Rα, and IL-21Rα1/2). Some paralogues have changes in domain structure and show differential expression, modulation, functions. IL-2 family cytokines constitutively express in many immune associated tissues and are largely induced after pathogenic microbial stimulation. In general, there are relatively conserved functions in the IL-2 family throughout vertebrates, and many of the key IL-2 family members are important in lymphocyte proliferation and differentiation, development, inflammation from fishes to mammals. This review will give an update on the effective information of teleost IL-2 family cytokines. Thus, it will provide a source of reference for other researchers/readers and inspire further interest.

Venetoclax-Resistant T-ALL Cells Display Distinct Cancer Stem Cell Signatures and Enrichment of Cytokine Signaling

Therapy resistance remains one of the major challenges for cancer treatment that largely limits treatment benefits and patient survival. The underlying mechanisms that lead to therapy resistance are highly complicated because of the specificity to the cancer subtype and therapy. The expression of the anti-apoptotic protein BCL2 has been shown to be deregulated in T-cell acute lymphoblastic leukemia (T-ALL), where different T-ALL cells display a differential response to the BCL2-specific inhibitor venetoclax. In this study, we observed that the expression of anti-apoptotic BCL2 family genes, such as BCL2, BCL2L1, and MCL1, is highly varied in T-ALL patients, and inhibitors targeting proteins coded by these genes display differential responses in T-ALL cell lines. Three T-ALL cell lines (ALL-SIL, MOLT-16, and LOUCY) were highly sensitive to BCL2 inhibition within a panel of cell lines tested. These cell lines displayed differential BCL2 and BCL2L1 expression. Prolonged exposure to venetoclax led to the development of resistance to it in all three sensitive cell lines. To understand how cells developed venetoclax resistance, we monitored the expression of BCL2, BCL2L1, and MCL1 over the treatment period and compared gene expression between resistant cells and parental sensitive cells. We observed a different trend of regulation in terms of BCL2 family gene expression and global gene expression profile including genes reported to be expressed in cancer stem cells. Gene set enrichment analysis (GSEA) showed enrichment of cytokine signaling in all three cell lines which was supported by the phospho-kinase array where STAT5 phosphorylation was found to be elevated in resistant cells. Collectively, our data suggest that venetoclax resistance can be mediated through the enrichment of distinct gene signatures and cytokine signaling pathways.

CRISPR-Cas9-AAV versus lentivector transduction for genome modification of X-linked severe combined immunodeficiency hematopoietic stem cells

Introduction

Ex vivo gene therapy for treatment of Inborn errors of Immunity (IEIs) have demonstrated significant clinical benefit in multiple Phase I/II clinical trials. Current approaches rely on engineered retroviral vectors to randomly integrate copy(s) of gene-of-interest in autologous hematopoietic stem/progenitor cells (HSPCs) genome permanently to provide gene function in transduced HSPCs and their progenies. To circumvent concerns related to potential genotoxicities due to the random vector integrations in HSPCs, targeted correction with CRISPR-Cas9-based genome editing offers improved precision for functional correction of multiple IEIs.

Methods

We compare the two approaches for integration of IL2RG transgene for functional correction of HSPCs from patients with X-linked Severe Combined Immunodeficiency (SCID-X1 or XSCID); delivery via current clinical lentivector (LV)-IL2RG versus targeted insertion (TI) of IL2RG via homology-directed repair (HDR) when using an adeno-associated virus (AAV)-IL2RG donor following double-strand DNA break at the endogenous IL2RG locus.

Results and discussion

In vitro differentiation of LV- or TI-treated XSCID HSPCs similarly overcome differentiation block into Pre-T-I and Pre-T-II lymphocytes but we observed significantly superior development of NK cells when corrected by TI (40.7% versus 4.1%, p = 0.0099). Transplants into immunodeficient mice demonstrated robust engraftment (8.1% and 23.3% in bone marrow) for LV- and TI-IL2RG HSPCs with efficient T cell development following TI-IL2RG in all four patients' HSPCs. Extensive specificity analysis of CRISPR-Cas9 editing with rhAmpSeq covering 82 predicted off-target sites found no evidence of indels in edited cells before (in vitro) or following transplant, in stark contrast to LV's non-targeted vector integration sites. Together, the improved efficiency and safety of IL2RG correction via CRISPR-Cas9-based TI approach provides a strong rationale for a clinical trial for treatment of XSCID patients.

Harnessing IL-15 signaling to potentiate NK cell-mediated cancer immunotherapy

Natural killer (NK) cells, a crucial component of the innate immune system, have long been of clinical interest for their antitumor properties. Almost every aspect of NK cell immunity is regulated by interleukin-15 (IL-15), a cytokine in the common γ-chain family. Several current clinical trials are using IL-15 or its analogs to treat various cancers. Moreover, NK cells are being genetically modified to produce membrane-bound or secretory IL-15. Here, we discuss the key role of IL-15 signaling in NK cell immunity and provide an up-to-date overview of IL-15 in NK cell therapy.

Murine myeloid derived suppressor cells possess a range of suppressive mechanisms-Granzyme B is not among them

This paper addresses the controversy of Granzyme B (GzmB) expression by murine Myeloid Derived Suppressor Cells (MDSCs). MDSCs are a heterogenous immature myeloid population that are generated in chronic inflammatory pathologies for the purpose to suppress inflammatory responses. MDSCs express a multitude of factors to induce suppressive function such as PD-L1, reactive oxygen species (ROS), nitric oxide synthase (iNOS), and Arginase-1. Recently, Dufait et al. sought to demonstrate GzmB as an additional mechanism for suppression by MDSCs. They reported that murine MDSCs not only significantly express GzmB as well as Perforin (Prf1), but this expression is functionally important for tumor growth in vivo as well as tumor migration in vitro. We conducted experiments to address the same question but made confounding observations: MDSCs under stringent developmental process do not express GzmB. Our results show that not only GzmB protein is not produced at functional level, but the mRNA transcript is not detectable either. In fact, the GzmB protein found in the media of MDSC culture was due to T cells or natural killer cells contained in bone marrow and cultured alongside MDSCs. We strengthen this finding by genetically deleting GzmB from the myeloid lineage and measuring tumor burden compared to WT counterpart. Our results show no significant difference in tumor burden, suggesting that even if there is minor expression of GzmB, it is not produced at a functional amount to affect tumor growth. Therefore, this paper proposes alternative theories that align with the known understanding of GzmB expression and secretion.

Natural Killer Cell Recognition and Control of Epithelial Cancers

Natural killer (NK) cells possess an innate ability to recognize cancer and are key mediators of cytotoxic efficacy for anticancer antibodies. Recent advances in the ability to generate, qualify, and safely infuse NK cells have led to a wide variety of clinical trials in oncology. Although their efficacy is best established for liquid cancers, their potential application in solid cancers has received increased attention. Here, we provide general background across a disparate group of exemplary solid tumors for which there is evidence for an NK cell role, discuss NK cell recognition motifs specific to each and murine and human studies of each that are supportive of NK cell adoptive immunotherapy, and end with special considerations relevant to the solid tumor microenvironment.

Advances of research of Fc-fusion protein that activate NK cells for tumor immunotherapy

The rapid development of bioengineering technology has introduced Fc-fusion proteins, representing a novel kind of recombinant protein, as promising biopharmaceutical products in tumor therapy. Numerous related anti-tumor Fc-fusion proteins have been investigated and are in different stages of development. Fc-fusion proteins are constructed by fusing the Fc-region of the antibody with functional proteins or peptides. They retain the bioactivity of the latter and partial properties of the former. This structural and functional advantage makes Fc-fusion proteins an effective tool in tumor immunotherapy, especially for the recruitment and activation of natural killer (NK) cells, which play a critical role in tumor immunotherapy. Even though tumor cells have developed mechanisms to circumvent the cytotoxic effect of NK cells or induce defective NK cells, Fc-fusion proteins have been proven to effectively activate NK cells to kill tumor cells in different ways, such as antibody-dependent cell-mediated cytotoxicity (ADCC), activate NK cells in different ways in order to promote killing of tumor cells. In this review, we focus on NK cell-based immunity for cancers and current research progress of the Fc-fusion proteins for anti-tumor therapy by activating NK cells.

CRISPR/Cas9-Mediated Insertion of HIV Long Terminal Repeat within BACH2 Promotes Expansion of T Regulatory-like Cells

One key barrier to curative therapies for HIV is the limited understanding of HIV persistence. HIV provirus integration sites (ISs) within BACH2 are common, and almost all sites mapped to date are located upstream of the start codon in the same transcriptional orientation as the gene. These unique features suggest the possibility of insertional mutagenesis at this location. Using CRISPR/Cas9-based homology-directed repair in primary human CD4+ T cells, we directly modeled the effects of HIV integration within BACH2 Integration of the HIV long terminal repeat (LTR) and major splice donor increased BACH2 mRNA and protein levels, altered gene expression, and promoted selective outgrowth of an activated, proliferative, and T regulatory-like cell population. In contrast, introduction of the HIV-LTR alone or an HIV-LTR-major splice donor construct into STAT5B, a second common HIV IS, had no functional impact. Thus, HIV LTR-driven BACH2 expression modulates T cell programming and leads to cellular outgrowth and unique phenotypic changes, findings that support a direct role for IS-dependent HIV-1 persistence.

The Interleukin-1 (IL-1) Superfamily Cytokines and Their Single Nucleotide Polymorphisms (SNPs)

Interleukins (ILs)—which are important members of cytokines—consist of a vast group of molecules, including a wide range of immune mediators that contribute to the immunological responses of many cells and tissues. ILs are immune-glycoproteins, which directly contribute to the growth, activation, adhesion, differentiation, migration, proliferation, and maturation of immune cells; and subsequently, they are involved in the pro and anti-inflammatory responses of the body, by their interaction with a wide range of receptors. Due to the importance of immune system in different organisms, the genes belonging to immune elements, such as ILs, have been studied vigorously. The results of recent investigations showed that the genes pertaining to the immune system undergo progressive evolution with a constant rate. The occurrence of any mutation or polymorphism in IL genes may result in substantial changes in their biology and function and may be associated with a wide range of diseases and disorders. Among these abnormalities, single nucleotide polymorphisms (SNPs) can represent as important disruptive factors. The present review aims at concisely summarizing the current knowledge available on the occurrence, properties, role, and biological consequences of SNPs within the IL-1 family members.

Tofacitinib Suppresses Natural Killer Cells In Vitro and In Vivo: Implications for Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal and incurable neurodegenerative disease with few therapeutic options. However, the immune system, including natural killer (NK) cells, is linked to ALS progression and may constitute a viable therapeutic ALS target. Tofacitinib is an FDA-approved immunomodulating small molecule which suppresses immune cell function by blocking proinflammatory cytokine signaling. This includes the cytokine IL-15 which is the primary cytokine associated with NK cell function and proliferation. However, the impact of tofacitinib on NK activation and cytotoxicity has not been thoroughly investigated, particularly in ALS. We therefore tested the ability of tofacitinib to suppress cytotoxicity and cytokine production in an NK cell line and in primary NK cells derived from control and ALS participants. We also investigated whether tofacitinib protected ALS neurons from NK cell cytotoxicity. Finally, we conducted a comprehensive pharmacokinetic study of tofacitinib in mice and tested the feasibility of administration formulated in chow. Success was assessed through the impact of tofacitinib on peripheral NK cell levels in mice. We found tofacitinib suppressed IL-15-induced activation as measured by STAT1 phosphorylation, cytotoxicity, pro-inflammatory gene expression, and pro-inflammatory cytokine secretion in both an NK cell line and primary NK cells. Furthermore, tofacitinib protected ALS neurons from NK cell-mediated cytotoxicity. In mice, we found tofacitinib bioavailability was 37% in both male and female mice; using these data we formulated mouse containing low and high doses of tofacitinib and found that the drug suppressed peripheral NK cell levels in a dose-dependent manner. These results demonstrate that tofacitinib can suppress NK cell function and may be a viable therapeutic strategy for ALS.

Emerging Canonical and Non-Canonical Roles of Granzyme B in Health and Disease

The Granzyme (Gzm) family has classically been recognized as a cytotoxic tool utilized by cytotoxic T lymphocytes (CTL) and natural killer (NK) cells to illicit cell death to infected and cancerous cells. Their importance is established based on evidence showing that deficiencies in these cell death executors result in defective immune responses. Recent findings have shown the importance of Granzyme B (GzmB) in regulatory immune cells, which may contribute to tumor growth and immune evasion during cancer development. Other studies have shown that members of the Gzm family are important for biological processes such as extracellular matrix remodeling, angiogenesis and organized vascular degradation. With this growing body of evidence, it is becoming more important to understand the broader function of Gzm's rather than a specific executor of cell death, and we should be aware of the many alternative roles that Gzm's play in physiological and pathological conditions. Therefore, we review the classical as well as novel non-canonical functions of GzmB and discuss approaches to utilize these new findings to address current gaps in our understanding of the immune system and tissue development.

Vγ5Vδ1 TCR signaling is required to different extents for embryonic versus postnatal development of DETCs

δγ T cells expressing Vγ5Vδ1 TCR originally develop in the embryonic thymus and migrate to the epidermis, forming dendritic epidermal T cells (DETCs) throughout life. It is thought that a TCR signal is essential for their development; e.g., lack of TCR signal-transducer ZAP70 significantly decreases DETC numbers. On the other hand, lack of ZAP70 does not affect Vγ5Vδ1 + T cells in the embryonic thymus; thus, the involvement of TCR signaling remains elusive. Here, we used SKG mice with attenuated TCR signaling rather than gene-knockout mice. In SKG mice, Vγ5 + T cells showed a marked decrease (10% of wild-type) in adult epidermis; however, there was just a moderate decrease (50% of wild-type) in the embryonic thymus. In early postnatal epidermis in SKG mice, substantial numbers of Vγ5 + T cells were observed (50% of wild-type). Their activation markers including CD122, a component of the IL-15 receptor indispensable for DETC proliferation, were comparable to those of WT. However, the Vγ5 + T cells in SKG mice did not proliferate and form DETCs thereafter. Furthermore, in SKG/+ mice, the number of thymic Vγ5Vδ1 + T cells increased, compared to SKG mice; however, the number of DETCs remained significantly lower than in WT, similar to SKG mice. Our results suggest that signaling via Vγ5Vδ1 TCR is indispensable for DETC development, with distinct contributions to embryonic development and postnatal proliferation.

miR-181a is a novel player in the STAT3-mediated survival network of TCRαβ+ CD8+ T large granular lymphocyte leukemia

T-LGL cells arise as a consequence of chronic antigenic stimulation and inflammation and thrive because of constitutive activation of the STAT3 and ERK pathway. Notably, in 40% of patients, constitutive STAT3 activation is due to STAT3 activating mutations, whereas in 60% this is unknown. As miRNAs are amongst the most potent regulators in health and disease, we hypothesized that aberrant miRNA expression could contribute to dysregulation of these pathways. miRNA sequencing in T-LGL leukemia cases and aged-matched healthy control TEMRA cells revealed overexpression of miR-181a. Furthermore, geneset enrichment analysis (GSEA) of downregulated targets of miR-181a implicated involvement in regulating STAT3 and ERK1/2 pathways. Flow cytometric analyses showed increased SOCS3+ and DUSP6+ T-LGL cells upon miR-181a inhibition. In addition, miR-181a-transfected human CD8+ T cells showed increased basal STAT3 and ERK1/2 phosphorylation. By using TL1, a human T-LGL cell line, we could show that miR-181a is an actor in T-LGL leukemia, driving STAT3 activation by SOCS3 inhibition and ERK1/2 phosphorylation by DUSP6 inhibition and verified this mechanism in an independent cell line. In addition, miR-181a inhibition resulted in a higher sensitivity to FAS-mediated apoptosis. Collectively, our data show that miR-181a could be the missing link to explain why STAT3-unmutated patients show hyperactive STAT3.

Therapeutic Potential of IL-15 and N-803 in HIV/SIV Infection

IL-15, a proinflammatory cytokine critical for the generation, maintenance, and homeostasis of T cell responses, is produced naturally in response to HIV/SIV infection, but has also demonstrated therapeutic potential. IL-15 can boost CD4+ and CD8+ T cell and NK cell proliferation, activation, and function. However, IL-15 treatment may cause aberrant immune activation and accelerated disease progression in certain circumstances. Moreover, the relationship between the timing of IL-15 administration and disease progression remains unclear. The IL-15 superagonist N-803 was developed to expand the therapeutic potential of IL-15 by maximizing its tissue distribution and half-life. N-803 has garnered enthusiasm recently as a way to enhance the innate and cellular immune responses to HIV/SIV by improving CD8+ T cell recognition and killing of virus-infected cells and directing immune cells to mucosal sites and lymph nodes, the primary sites of virus replication. N-803 has also been evaluated in "shock and kill" strategies due to its potential to reverse latency (shock) and enhance antiviral immunity (kill). This review examines the current literature about the effects of IL-15 and N-803 on innate and cellular immunity, viral burden, and latency reversal in the context of HIV/SIV, and their therapeutic potential both alone and combined with additional interventions such as antiretroviral therapy (ART) and vaccination.

ZIPK activates the IL-6/STAT3 signaling pathway and promotes cisplatin resistance in gastric cancer cells

Gastric cancer is one of the most common malignant cancers globally. Chemotherapy resistance remains a major obstacle in the treatment of gastric cancer, and the molecular mechanisms underlying drug resistance are still not well understood. We previously reported that Zipper interacting protein kinase (ZIPK), also known as death‐associated protein kinase3, exerts an oncogenic effect on gastric cancer via activation of Akt/NF‐κB signaling and promotion of stemness. Here, we explored the roles of ZIPK in cisplatin resistance. We report that ZIPK enhances cell proliferation and invasion and reduces the antitumor activity of cisplatin in gastric cancer. In addition, our western blot data suggest that ZIPK activated the IL‐6/STAT3 signaling pathway. Furthermore, ZIPK increased the expression of IL‐6 and multidrug‐resistance genes. Using the STAT3 inhibitor stattic to block the IL‐6/STAT3 signaling pathway strongly increased the sensitivity of ZIPK‐expressed cells to cisplatin. In conclusion, ZIPK may play a role in cisplatin resistance through activation of the IL‐6/ STAT3 signaling pathway. Inhibition of STAT3 in gastric cancer overexpressing ZIPK might have potential to improve the efficacy of cisplatin.

Skeletal Muscle O-GlcNAc Transferase Action on Global Metabolism Is Partially Mediated Through Interleukin-15

Besides its roles in locomotion and thermogenesis, skeletal muscle plays a significant role in global glucose metabolism and insulin sensitivity through complex nutrient sensing networks. Our previous work showed that the muscle-specific ablation of O-GlcNAc transferase (OGT) led to a lean phenotype through enhanced interleukin-15 (IL-15) expression. We also showed OGT epigenetically modified and repressed the Il15 promoter. However, whether there is a causal relationship between OGT ablation-induced IL-15 secretion and the lean phenotype remains unknown. To address this question, we generated muscle specific OGT and interleukin-15 receptor alpha subunit (IL-15rα) double knockout mice (mDKO). Deletion of IL-15rα in skeletal muscle impaired IL-15 secretion. When fed with a high-fat diet, mDKO mice were no longer protected against HFD-induced obesity compared to wild-type mice. After 22 weeks of HFD feeding, mDKO mice had an intermediate body weight and glucose sensitivity compared to wild-type and OGT knockout mice. Taken together, these data suggest that OGT action is partially mediated by muscle IL-15 production and provides some clarity into how disrupting the O-GlcNAc nutrient signaling pathway leads to a lean phenotype. Further, our work suggests that interfering with the OGT-IL15 nutrient sensing axis may provide a new avenue for combating obesity and metabolic disorders.

Approaches to Enhance Natural Killer Cell-Based Immunotherapy for Pediatric Solid Tumors

Treatment of metastatic pediatric solid tumors remain a significant challenge, particularly in relapsed and refractory settings. Standard treatment has included surgical resection, radiation, chemotherapy, and, in the case of neuroblastoma, immunotherapy. Despite such intensive therapy, cancer recurrence is common, and most tumors become refractory to prior therapy, leaving patients with few conventional treatment options. Natural killer (NK) cells are non-major histocompatibility complex (MHC)-restricted lymphocytes that boast several complex killing mechanisms but at an added advantage of not causing graft-versus-host disease, making use of allogeneic NK cells a potential therapeutic option. On top of their killing capacity, NK cells also produce several cytokines and growth factors that act as key regulators of the adaptive immune system, positioning themselves as ideal effector cells for stimulating heavily pretreated immune systems. Despite this promise, clinical efficacy of adoptive NK cell therapy to date has been inconsistent, prompting a detailed understanding of the biological pathways within NK cells that can be leveraged to develop "next generation" NK cell therapies. Here, we review advances in current approaches to optimizing the NK cell antitumor response including combination with other immunotherapies, cytokines, checkpoint inhibition, and engineering NK cells with chimeric antigen receptors (CARs) for the treatment of pediatric solid tumors.

STAT3 determines IL-4 signalling outcomes in naïve T cells

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

Dynamic Roles for IL-2-STAT5 Signaling in Effector and Regulatory CD4+ T Cell Populations

CD4⁺ Th cells are responsible for orchestrating diverse, pathogen-specific immune responses through their differentiation into a number of subsets, including T_H1, T_H2, T_H9, T follicular helper, T follicular regulatory, and regulatory T cells. The differentiation of each subset is guided by distinct regulatory requirements, including those derived from extracellular cytokine signals. IL-2 has emerged as a critical immunomodulatory cytokine that both positively and negatively affects the differentiation of individual Th cell subsets. IL-2 signals are propagated, in part, via activation of STAT5, which functions as a key regulator of CD4⁺ T cell gene programs. In this review, we discuss current understanding of the mechanisms that allow IL-2-STAT5 signaling to exert divergent effects across CD4⁺ T cell subsets and highlight specific roles for this pathway in the regulation of individual Th cell differentiation programs.

Integration of IL-2 and IL-4 signals coordinates divergent regulatory T cell responses and drives therapeutic efficacy

Cells exist within complex milieus of communicating factors, such as cytokines, that combine to generate context-specific responses, yet nearly all knowledge about the function of each cytokine and the signaling propagated downstream of their recognition is based on the response to individual cytokines. Here, we found that regulatory T cells (Tregs) integrate concurrent signaling initiated by IL-2 and IL-4 to generate a response divergent from the sum of the two pathways in isolation. IL-4 stimulation of STAT6 phosphorylation was blocked by IL-2, while IL-2 and IL-4 synergized to enhance STAT5 phosphorylation, IL-10 production, and the selective proliferation of IL-10-producing Tregs, leading to increased inhibition of conventional T cell activation and the reversal of asthma and multiple sclerosis in mice. These data define a mechanism of combinatorial cytokine signaling and lay the foundation upon which to better understand the origins of cytokine pleiotropy while informing improved the clinical use of cytokines.

IL-15 Improves Aging-Induced Persistent T Cell Exhaustion in Mouse Models of Repeated Sepsis

Aging is a grave problem in sepsis, and T cell exhaustion is the main cause of sepsis-induced immunosuppression. Sepsis- and aging-induced T cell exhaustion is related to secondary infection with a poor long-term outcome in the elderly. However, the trend, impact, and mechanism of T cell exhaustion are still unclear. Interleukin (IL)-15 improves survival rate of septic mice via its antiapoptotic effect on T cells; however, it is still unclear how IL-15 reverses prolonged T cell exhaustion in aged septic mice. The purpose of this study was to clarify the trend of sepsis-induced T cell exhaustion and whether IL-15 prevents aging-induced persistent T cell exhaustion in septic mice. Preserved cecal slurry was injected intraperitoneally into young (6-week-old) and aged mice (18-24-month-old) 4 times, to induce clinically relevant repeated sepsis. IL-15 (1.5 μg) or phosphate-buffered saline was injected subcutaneously 3 times, body weight was serially measured, and peripheral blood cells from their cheek were serially collected for 50 days. Sepsis-induced T cell exhaustion was significantly severe in aged mice than in young mice and was accompanied with decreased naive CD4 and CD8 T cells (P < 0.01) and increased expression of program death 1 on T cell (P < 0.01) and regulatory T cell population (P < 0.01). IL-15 significantly improved sepsis-induced T exhaustion, with significantly increased numbers of natural killer cells and macrophages, and significantly enhanced phagocytosis activity in aged septic mice (P < 0.05). It decreased the long-term mortality associated with sepsis survivors by improving T cell exhaustion over an extended duration and also ameliorated aging-induced persistent T cell exhaustion in septic mice.

Clinical outcomes in T-cell large granular lymphocytic leukaemia: prognostic factors and treatment response

T-cell large granular lymphocytic leukaemia (T-LGLL) is an incurable leukaemia characterised by clonal proliferation of abnormal cytotoxic T cells that can result in severe neutropenia, transfusion-dependent anaemia and pancytopenia requiring treatment. The most commonly used agents, methotrexate (MTX), cyclophosphamide (Cy) and cyclosporine primarily produce partial remissions (PRs), with few complete responses (CRs). We evaluated the clinical course and treatment response of 60 consecutive patients with T-LGLL to evaluate clinical outcomes and future potential treatment directions. Impaired overall survival was noted among male patients, patients with elevated lactate dehydrogenase, and those without rheumatoid arthritis. Cy was the most efficacious second-line agent, with a 70% overall response rate (ORR; three CR, four PR). All patients who failed frontline MTX responded to second-line Cy. In the relapsed or Cy-refractory setting, alemtuzumab (n = 4) and pentostatin (n = 3) had an ORR of 50% and 66%, respectively, while duvelisib induced a long-term response in one patient. In this large, retrospective analysis, our results suggest Cy is a highly effective therapy for second-line treatment in T-LGLL and should be considered a strong candidate for up-front therapy in select high-risk patients. Prospective studies evaluating pentostatin, alemtuzumab and novel agents, such as duvelisib, are needed for patients with relapsed/refractory T-LGLL.

Gliadin, through the Activation of Innate Immunity, Triggers lncRNA NEAT1 Expression in Celiac Disease Duodenal Mucosa

Celiac disease (CD) is an autoimmune enteropathy arising in genetically predisposed subjects exposed to gluten, which activates both innate and adaptive immunity. Although the pathogenesis is common to all patients, the clinical spectrum is quite variable, and differences could be explained by gene expression variations. Among the factors able to affect gene expression, there are lncRNAs. We evaluated the expression profile of 87 lncRNAs in CD vs. healthy control (HC) intestinal biopsies by RT-qPCR array. Nuclear enriched abundant transcript 1 (NEAT1) and taurine upregulated gene 1 (TUG1) were detected as downregulated in CD patients at diagnosis, but their expression increased in biopsies of patients on a gluten-free diet (GFD) exposed to gluten. The increase in NEAT1 expression after gluten exposure was mediated by IL-15 and STAT3 activation and binding to the NEAT1 promoter, as demonstrated by gel shift assay. NEAT1 is localized in the nucleus and can regulate gene expression by sequestering transcription factors, and it has been implicated in immune regulation and control of cell proliferation. The demonstration of its regulation by gluten thus also supports the role of lncRNAs in CD and prompts further research on these RNAs as gene expression regulators.

Modulation of CD4 T Cell Response According to Tumor Cytokine Microenvironment

The advancement of knowledge on tumor biology over the past decades has demonstrated a close link between tumor cells and cells of the immune system. In this context, cytokines have a major role because they act as intermediaries in the communication into the tumor bed. Cytokines play an important role in the homeostasis of innate and adaptive immunity. In particular, they participate in the differentiation of CD4 T lymphocytes. These cells play essential functions in the anti-tumor immune response but can also be corrupted by tumors. The differentiation of naïve CD4 T cells depends on the cytokine environment in which they are activated. Additionally, at the tumor site, their activity can also be modulated according to the cytokines of the tumor microenvironment. Thus, polarized CD4 T lymphocytes can see their phenotype evolve, demonstrating functional plasticity. Knowledge of the impact of these cytokines on the functions of CD4 T cells is currently a source of innovation, for therapeutic purposes. In this review, we discuss the impact of the major cytokines present in tumors on CD4 T cells. In addition, we summarize the main therapeutic strategies that can modulate the CD4 response through their impact on cytokine production.

Intravitreal Interleukin-2 modifies retinal excitatory circuits and retinocollicular innervation

Interleukin-2 is a classical immune cytokine whose neural functions have received little attention. Its levels have been found to be increased in some neuropathologies, such as Alzheimer's disease, multiple sclerosis and uveitis. Mechanistically, it has been demonstrated the role of IL-2 in regulating glutamate and acetylcholine transmission, thus being relevant for CNS physiology. In fact, our previous work showed that an acute intravitreal IL-2 injection during retinotectal development promoted contralateral eye axonal plasticity in the superior colliculus, but the involved mechanisms were not explored. So, our present study aimed to investigate the effect of increased intravitreal IL-2 levels on the retinal glutamatergic and cholinergic signalling required for retinotectal normal development. We showed through HRP neuronal tracing that intravitreal IL-2 also induces ipsilateral eye axonal sprouting. Protein level and/or immunolocalization analysis in the retina confirmed IL-2 pathway activation by increased expression of phospho-STAT-3, coupled to transient (24h) reduced levels of Egr1, PSD-95 and nicotinic acetylcholine receptor β2 subunit, suggesting reduced neural activity and synaptic sites. Also, AChE activity and GluN2B and GluA2 contents were reduced within 96h after IL-2 treatment. Therefore, IL-2-induced retinotectal plasticity might be driven by changes in cholinergic and glutamatergic pathways of the retina.

Divergent Role for STAT5 in the Adaptive Responses of Natural Killer Cells

Natural killer (NK) cells are innate lymphocytes with the capacity to elicit adaptive features, including clonal expansion and immunological memory. Because signal transducer and activator of transcription 5 (STAT5) is essential for NK cell development, the roles of this transcription factor and its upstream cytokines interleukin-2 (IL-2) and IL-15 during infection have not been carefully investigated. In this study, we investigate how STAT5 regulates transcription during viral infection. We demonstrate that STAT5 is induced in NK cells by IL-12 and STAT4 early after infection and that partial STAT5 deficiency results in a defective capacity of NK cells to generate long-lived memory cells. Furthermore, we find a functional dichotomy of IL-2 and IL-15 signaling outputs during viral infection, whereby both cytokines drive clonal expansion, but only IL-15 is required for memory NK cell survival. We thus highlight a role for STAT5 signaling in promoting an optimal anti-viral NK cell response.

Wiedemann et al. demonstrate that Stat5a and Stat5b are induced by IL-12 and STAT4 signaling in NK cells following MCMV infection. They further provide evidence that the cytokines IL-2 and IL-15 upstream of STAT5 differentially promote the early and late stages of the adaptive NK cell response to MCMV infection.

Identification of a γc Receptor Antagonist That Prevents Reprogramming of Human Tissue-resident Cytotoxic T Cells by IL15 and IL21

BACKGROUND & AIMS

Gamma chain (γc) cytokines (interleukin [IL]2, IL4, IL7, IL9, IL15, and IL21) signal via a common γc receptor. IL2 regulates the immune response, whereas IL21 and IL15 contribute to development of autoimmune disorders, including celiac disease. We investigated whether BNZ-2, a peptide designed to inhibit IL15 and IL21, blocks these cytokines selectively and its effects on intraepithelial cytotoxic T cells.

METHODS

We obtained duodenal biopsies from 9 patients with potential celiac disease (positive results from tests for anti-TG2 but no villous atrophy), 30 patients with untreated celiac disease (with villous atrophy), and 5 patients with treated celiac disease (on a gluten-free diet), as well as 43 individuals without celiac disease (controls). We stimulated primary intestinal intraepithelial CD8⁺ T-cell lines, or CD8⁺ T cells directly isolated from intestinal biopsies, with γc cytokines in presence or absence of BNZ-2. Cells were analyzed by immunoblots, flow cytometry, or RNA-sequencing analysis for phosphorylation of signaling molecules, gene expression profiles, proliferation, and levels of granzyme B.

RESULTS

Duodenal tissues from patients with untreated celiac disease had increased levels of messenger RNAs encoding IL15 receptor subunit alpha (IL15RA) and IL21 compared with tissues from patients with potential celiac disease and controls. Activation of intraepithelial cytotoxic T cells with IL15 or IL21 induced separate signaling pathways; incubation of the cells with IL15 and IL21 cooperatively increased their transcriptional activity, proliferation, and cytolytic properties. BNZ-2 specifically inhibited the effects of IL15 and IL21, but not of other γc cytokines.

CONCLUSIONS

We found increased expression of IL15RA and IL21 in duodenal tissues from patients with untreated celiac disease compared with controls. IL15 and IL21 cooperatively activated intestinal intraepithelial cytotoxic T cells. In particular, they increased their transcriptional activity, proliferation, and cytolytic activity. The peptide BNZ-2 blocked these effects, but not those of other γc cytokines, including IL2. BNZ-2 might be used to prevent cytotoxic T-cell-mediated tissue damage in complex immune disorders exhibiting upregulation of IL15 and IL21.

IL-15Rα membrane anchorage in either cis or trans is required for stabilization of IL-15 and optimal signaling

Interleukin (IL)-15 plays an important role in the communication between immune cells. It delivers its signal through different modes involving three receptor chains: IL-15Rα, IL-2Rβ and IL-2Rγc. The combination of the different chains result in the formation of IL-15Rα/IL-2Rβ/γc trimeric or IL-2Rβ/γc dimeric receptors. In this study, we have investigated the role of the IL-15Rα chain in stabilizing the cytokine in the IL-2Rβ/γc dimeric receptor. By analyzing the key amino acid residues of IL-15 facing IL-2Rβ, we provide evidence of differential interfaces in the presence or in the absence of membrane-anchored IL-15Rα. Moreover, we found that the anchorage of IL-15Rα to the cell surface regardless its mode of presentation - i.e. cis or trans - is crucial for complete signaling. These observations show how the cells can finely modulate the intensity of cytokine signaling through the quality and the level of expression of the receptor chains.

Mechanistic and Structural Insights on the IL-15 System through Molecular Dynamics Simulations

Interleukin 15 (IL-15), a four-helix bundle cytokine, is involved in a plethora of different cellular functions and, particularly, plays a key role in the development and activation of immune responses. IL-15 forms receptor complexes by binding with IL-2Rβ- and common γ (γc)-signaling subunits, which are shared with other members of the cytokines family (IL-2 for IL-2Rβ- and all other γc- cytokines for γc). The specificity of IL-15 is brought by the non-signaling α-subunit, IL-15Rα. Here we present the results of molecular dynamics simulations carried out on four relevant forms of IL-15: its monomer, IL-15 interacting individually with IL-15Rα (IL-15/IL-15Rα), with IL-2Rβ/γc subunits (IL-15/IL-2Rβ/γc) or with its three receptors simultaneously (IL-15/IL-15Rα/IL-2Rβ/γc). Through the analyses of the various trajectories, new insights on the structural features of the interfaces are highlighted, according to the considered form. The comparison of the results with the experimental data, available from X-ray crystallography, allows, in particular, the rationalization of the importance of IL-15 key residues (e.g., Asp8, Lys10, Glu64). Furthermore, the pivotal role of water molecules in the stabilization of the various protein-protein interfaces and their H-bonds networks are underlined for each of the considered complexes.

Signaling and Function of Interleukin-2 in T Lymphocytes

The discovery of interleukin-2 (IL-2) changed the molecular understanding of how the immune system is controlled. IL-2 is a pleiotropic cytokine, and dissecting the signaling pathways that allow IL-2 to control the differentiation and homeostasis of both pro- and anti-inflammatory T cells is fundamental to determining the molecular details of immune regulation. The IL-2 receptor couples to JAK tyrosine kinases and activates the STAT5 transcription factors. However, IL-2 does much more than control transcriptional programs; it is a key regulator of T cell metabolic programs. The development of global phosphoproteomic approaches has expanded the understanding of IL-2 signaling further, revealing the diversity of phosphoproteins that may be influenced by IL-2 in T cells. However, it is increasingly clear that within each T cell subset, IL-2 will signal within a framework of other signal transduction networks that together will shape the transcriptional and metabolic programs that determine T cell fate.

Oxidative stress-induced IL-15 trans-presentation in keratinocytes contributes to CD8+ T cells activation via JAK-STAT pathway in vitiligo

Oxidative stress and effector memory CD8⁺ T cells have been greatly implicated in vitiligo pathogenesis. However, the crosstalk between these two crucial pathogenic factors has been merely investigated. IL-15 has been regarded as an important cytokine exerting its facilitative effect on memory CD8⁺ T cells function in various autoimmune diseases. In the present study, we initially discovered that the IL-15 expression was significantly increased in vitiligo epidermis and highly associated with epidermal H₂O₂ content. In addition, epidermal IL-15 expression was mainly derived from keratinocytes. Then, we showed that oxidative stress promoted IL-15 and IL-15Rα expression as well as IL-15 trans-presentation by activating NF-κB signaling in keratinocytes. What's more, the trans-presented IL-15, rather than the secreted one, was accounted for the potentiation of CD8⁺ T_EMs activation. We further investigated the mechanism underlying trans-presented IL-15 in potentiating CD8⁺ T_EMs activation and found that the blockage of IL-15-JAK-STAT signaling could be a potent therapeutic approach. Taken together, our results demonstrate that oxidative stress-induced IL-15 trans-presentation in keratinocytes contributes to the activation of CD8⁺ T_EMs, providing a novel mechanism by which oxidative stress initiates autoimmunity in vitiligo.

Sepsis: Inflammation Is a Necessary Evil

Sepsis is one of the leading causes of deaths world-wide and yet there are no therapies available other than ICU treatment. The patient outcome is determined by a complex interplay between the pro and anti-inflammatory responses of the body i.e., a homeostatic balance between these two competing events to be achieved for the patient’s recovery. The initial attempts on drug development mainly focused on controlling inflammation, however, without any tangible outcome. This was despite most deaths occurring during the immune paralysis stage of this biphasic disease. Recently, the focus has been shifting to understand immune paralysis (caused by apoptosis and by anti-inflammatory cytokines) to develop therapeutic drugs. In this review we put forth an argument for a proper understanding of the molecular basis of inflammation as well as apoptosis for developing an effective therapy.

Interleukin-15 as a myokine: mechanistic insight into its effect on skeletal muscle metabolism

Interleukin (IL)-15 is a cytokine with important immunological functions. It is highly expressed in skeletal muscle and is believed to be a myokine, a hypothesis supported by the rapid increase in circulating levels of IL-15 in response to exercise. Treatment with high doses of IL-15 results in metabolic adaptations such as improved insulin sensitivity and whole-body fatty acid oxidation and protection from high-fat-diet-induced obesity and insulin resistance. IL-15 secreted by contracting muscle may therefore act as an endocrine factor to improve adiposity and energy metabolism in different tissues. Most studies have used supraphysiological doses of IL-15 that do not represent circulating IL-15 in response to exercise. However, evidence shows that IL-15 levels are higher in muscle interstitium and that IL-15 might improve muscle glucose homeostasis and oxidative metabolism in an autocrine/paracrine manner. Nevertheless, how IL-15 signals in skeletal muscle to improve muscle energy metabolism is not understood completely, especially because the absence of the α subunit of the IL-15 receptor (IL-15Rα) results in a phenotype similar to that of overexpressing/oversecreting IL-15 in mice. In this article, we review the literature to propose a model for the regulation of IL-15 by the soluble form of IL-15Rα to explain why some findings in the literature seem, at first glance, to be contradictory.

The role of cytokines in the regulation of NK cells in the tumor environment

Natural killer (NK) cells are innate lymphoid cells that are important effectors in the first line of defense toward transformed cells. This is mediated both by direct cytotoxic mechanisms and by production of immunoregulatory cytokines. Recent evidence has shown that NK cells also display memory, similar to the cells of the adaptive immune system. Cytokines are pivotal for the maturation, activation and survival of NK cells. Interleukins (IL)-2, IL-12, IL-15, IL-18, IL-21 and type I interferons positively regulate NK cell function, either independently or in cooperation, whereas other cytokines, such as IL-23 and IL-27, may enhance or suppress NK cell function depending on the context. In the tumor microenvironment, TGFβ, IL-10 and IL-6 suppress NK cell activity not only directly, but also indirectly, by affecting immunosuppressive cells and by antagonizing the effect of stimulatory cytokines, thereby dampening the antitumor response of NK cells and promoting subsequent tumor evasion and progression. Increased understanding of the NK cell response to cytokines has provided a better understanding of their impaired function in tumors which may aid in the development of novel immunotherapeutic strategies to enhance NK cell responses in cancer patients.

A novel strategy to produce high level and high purity of bioactive IL15 fusion proteins from mammalian cells

IL15, a member of the common γ chain receptor (γc) cytokine family, is gaining attention in recent years as one of the most promising anti-tumor agents. IL15 regulates T cell activation and proliferation, promotes the survival of CD8⁺ CD44^hi memory T cells and is also essential for NK cell expansion and development. Despite the attraction of developing IL15 as an anti-cancer agent, production of recombinant IL15 has proven to be difficult due to the stringent control of IL15 expression at the transcriptional, translational and the post-translational levels. Furthermore, the bioactivity of IL15 fused to an extra functional domain that is isolated from mammalian cells is generally inferior to recombinant IL15 produced by E. coli. In this study, we report that Lysine 86 in IL15 is responsible for the instability in mammalian cells when its C-terminus is fused to the albumin binding scFv (IL15-A10m3). We demonstrate that K86A or K86R mutants increased the expression of the fusion protein from HEK293 cells. When the wild type IL15 is used for the fusion, no recombinant IL15 fusion was detected in the culture media. Additionally, we determined that the residue 112 in IL15 is critical for the bioactivity of IL15-A10m3. Examination of single and double mutants provides a better understanding of how IL15 engages with its receptor complex to achieve full signaling capacity. The results of our experiments were successfully applied to scale up production to levels up to 50 mg/L and >10 mg/L of >95% pure monomeric recombinant fusion proteins after a 2-step purification from culture media. More importantly, the recombinant fusion protein produced is fully active in stimulating T cell proliferation, when compared to the recombinant wild type IL15.

Out-sourcing for Trans-presentation: Assessing T Cell Intrinsic and Extrinsic IL-15 Expression with Il15 Gene Reporter Mice

IL-15 is a cytokine of the common γ-chain family that is critical for natural killer (NK), invariant natural killer T (iNKT), and CD8 memory T cell development and homeostasis. The role of IL-15 in regulating effector T cell subsets, however, remains incompletely understood. IL-15 is mostly expressed by stromal cells, myeloid cells, and dendritic cells (DCs). Whether T cells themselves can express IL-15, and if so, whether such T cell-derived IL-15 could play an autocrine role in T cells are interesting questions that were previously addressed but answered with mixed results. Recently, three independent studies described the generation of IL-15 reporter mice which facilitated the identification of IL-15-producing cells and helped to clarify the role of IL-15 both in vitro and in vivo. Here, we review the findings of these studies and place them in context of recent reports that examined T cell-intrinsic IL-15 expression during CD4 effector T cell differentiation.

The Growth Hormone Receptor: Mechanism of Receptor Activation, Cell Signaling, and Physiological Aspects

The growth hormone receptor (GHR), although most well known for regulating growth, has many other important biological functions including regulating metabolism and controlling physiological processes related to the hepatobiliary, cardiovascular, renal, gastrointestinal, and reproductive systems. In addition, growth hormone signaling is an important regulator of aging and plays a significant role in cancer development. Growth hormone activates the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling pathway, and recent studies have provided a new understanding of the mechanism of JAK2 activation by growth hormone binding to its receptor. JAK2 activation is required for growth hormone-mediated activation of STAT1, STAT3, and STAT5, and the negative regulation of JAK-STAT signaling comprises an important step in the control of this signaling pathway. The GHR also activates the Src family kinase signaling pathway independent of JAK2. This review covers the molecular mechanisms of GHR activation and signal transduction as well as the physiological consequences of growth hormone signaling.

Epigenetic Maintenance of Acquired Gene Expression Programs during Memory CD8 T Cell Homeostasis

Memory CD8 T cells have a unique ability to provide lifelong immunity against pathogens containing their cognate epitope. Because of their ability to provide lifelong protection, the generation of memory T cells is now a major focus for current vaccination or adoptive cell therapy approaches to treat chronic viral infections and cancer. It is now clear that maintenance of memory CD8 T cells occurs through a process of antigen-independent homeostatic proliferation, which is regulated in part by the gamma chain cytokines IL-7 and IL-15. Here, we will describe the role of these cytokines in the survival and self-renewal of memory CD8 T cells. Further, we will describe the role of epigenetics in the maintenance of acquired functions among memory CD8 T cells during homeostatic proliferation.

Interleukin-15 derived from Guanylin-GC-C-expressing macrophages inhibits fatty acid synthase in adipocytes

Recently we found that guanylin (Gn) and its receptor, guanylyl cyclase C (GC-C), are uniquely expressed in the mesenteric macrophages of some diet-resistant rats and that double-transgenic (dTg) rats overexpressing Gn and GC-C in macrophages demonstrate reduced fatty acid synthase and fat accumulation in fat tissue even when fed a high-fat diet (HFD). Lipid accumulation and fatty acid synthase mRNA levels in cocultured dTg rat adipocytes and macrophages were reduced compared with those in adipocytes cultured with WT rat macrophages. Here, we investigated whether Interleukin-15 (IL-15) derived from Gn-GC-C-expressing macrophages regulates lipid accumulation in adipocytes. IL-15 inhibited fatty acid synthase and lipid accumulation via STAT5 in cultured adipocytes. IL-15 mRNA and protein levels in the mesenteric fat of HFD-fed dTg rats were significantly higher than those of HFD-fed WT rats. Phosphorylated STAT5 levels in the mesenteric fat of HFD-fed dTg rats were increased compared with those of HFD-fed WT rats. In addition, the mRNA level of fatty acid synthase in the mesenteric fat was lower in HFD-fed dTg rats than in HFD-fed WT rats. These results support the hypothesis that IL-15 secreted from Gn-GC-C-expressing macrophages contributes to the inhibition of fatty acid synthase and lipid accumulation in adipocytes, leading to obesity resistance.