Interleukin 21 and its receptor are involved in NK cell expansion and regulation of lymphocyte function

Identification of targets for prostate cancer immunotherapy

BACKGROUND

We performed profiling of the immune microenvironment of castration-resistant (CRPC) and castration-sensitive (CSPC) prostate cancer (PC) in order to identify novel targets for immunotherapy.

METHODS

PD-L1 and CD3/CD8 immunohistochemistry, PD-L1/2 fluorescent in situ hybridization, tumor mutation burden, microsatellite instability, and RNA-seq of 395 immune-related genes were performed in 19 CRPC and CSPC. Targeted genomic sequencing and fusion analysis were performed in 17 of these specimens.

RESULTS

CD276, PVR, and NECTIN2 were highly expressed in PC. Comparison of CRPC versus CSPC and primary versus metastatic tissue revealed the differential expression of immunostimulatory, immunosuppressive, and epithelial-to-mesenchymal transition (EMT)-related genes. Unsupervised clustering of differentially expressed genes yielded two final clusters best segregated by CRPC and CSPC status.

CONCLUSION

CD276 and the alternative checkpoint inhibition PVR/NECTIN2/CD226/TIGIT pathway emerged as relevant to PC checkpoint inhibition target development.

Circulating CXCR3-CCR6-CXCR5+CD4+ T cells are associated with acute allograft rejection in liver transplantation

Circulating T follicular helper (cTFH) cells have been demonstrated to be involved in B-cell-mediated alloreactive responses in kidney and liver transplantation; however, whether these cells are involved in acute liver allograft rejection after liver transplantation, and which subsets are involved, remains to be clarified. The present study aimed to investigate the profiles of cTFH cells in acute liver allograft rejection, including the CXC motif receptor 3 (CXCR3)⁺ chemokine receptor 6 (CCR6)^- subset, the CXCR3^-CCR6^- subset, and the CXCR3^-CCR6⁺ subset. Twelve liver transplant patients with acute rejection (AR) and 20 with no acute rejection (NAR) were enrolled in the study. The results showed that the proportion of CXCR3-CCR6-CXCR5⁺CD4⁺ T cells was significantly increased and the proportion of CXCR3^-CCR6⁺CXCR5⁺CD4⁺ T cells was significantly decreased in patients with AR compared with patients with NAR. In addition, the proportion of CXCR3-CCR6-CXCR5⁺CD4⁺ T cells was positively correlated with the proportion of B cells in patients with AR. The level of serum interleukin (IL)-21 was higher in the AR group than in the NAR groups. Furthermore, the proportion of CXCR3-CCR6-CXCR5⁺CD4⁺ T cells was positively correlated with alanine amino transferase (ALT), whereas the proportion of CXCR3^-CCR6⁺ CXCR5⁺CD4⁺ T cells was negatively correlated with ALT. B cells and TFH cells were detected in follicular-like structures in liver allograft tissues from patients with AR. These results suggest that CXCR3-CCR6-CXCR5⁺CD4⁺ T cells may be involved in acute allograft rejection after liver transplantation.

Fueling Cancer Immunotherapy With Common Gamma Chain Cytokines

Adoptive T cell transfer therapy (ACT) using tumor infiltrating lymphocytes or lymphocytes redirected with antigen receptors (CAR or TCR) has revolutionized the field of cancer immunotherapy. Although CAR T cell therapy mediates robust responses in patients with hematological malignancies, this approach has been less effective for treating patients with solid tumors. Additionally, toxicities post T cell infusion highlight the need for safer ACT protocols. Current protocols traditionally expand T lymphocytes isolated from patient tumors or from peripheral blood to large magnitudes in the presence of high dose IL-2 prior to infusion. Unfortunately, this expansion protocol differentiates T cells to a full effector or terminal phenotype in vitro, consequently reducing their long-term survival and antitumor effectiveness in vivo. Post-infusion, T cells face further obstacles limiting their persistence and function within the suppressive tumor microenvironment. Therapeutic manipulation of T cells with common γ chain cytokines, which are critical growth factors for T cells, may be the key to bypass such immunological hurdles. Herein, we discuss the primary functions of the common γ chain cytokines impacting T cell survival and memory and then elaborate on how these distinct cytokines have been used to augment T cell-based cancer immunotherapy.

Clinical significance and immunobiology of IL-21 in autoimmunity

Interleukin-21 (IL-21), an autocrine cytokine predominantly produced by follicular helper T (Tfh) and T helper 17 (Th17) cells, has been proven to play an important role in the immune system, for example, by promoting proliferation and the development of Tfh and Th17 cells, balancing helper T cell subsets, inducing B cell generation and differentiation into plasma cells, and enhancing the production of immunoglobulin. These effects are mainly mediated by activation of the JAK/STAT, MAPK and PI3K pathways. Some IL-21 target genes, such as B lymphocyte induced maturation protein-1 (Blimp-1), suppressor of cytokine signaling (SOCS), CXCR5 and Bcl-6, play important roles in the immune response. Therefore, IL-21 has been linked to autoimmune diseases. Indeed, IL-21 levels are increased in the peripheral blood and tissues of patients with systematic lupus erythematosus (SLE), rheumatoid arthritis (RA), type 1 diabetes (T1D), immune thrombocytopenia (ITP), primary Sjogren's syndrome (pSS), autoimmune thyroid disease (AITD) and psoriasis. This increased IL-21 even positively associates with Tfh cells, plasma cells, autoantibodies and disease activity in SLE and RA. Additionally, IL-21 has been utilized as a therapeutic target in SLE, RA, T1D and psoriatic mouse models. Profoundly, clinical trials have shown safety and improvement in RA patients. However, tolerance and long-term pharmacodynamics effects with low bioavailability have been found in SLE patients. Therefore, this review aims to summarize the latest progress on IL-21 function and its signaling pathway and discuss the role of IL-21 in the pathogenesis of and therapy for autoimmune diseases, with the hope of providing potential therapeutic and diagnostic strategies for clinical use.

Overcoming Resistance to Natural Killer Cell Based Immunotherapies for Solid Tumors

Despite advances in the diagnostic and therapeutic modalities, the prognosis of several solid tumor malignancies remains poor. Different factors associated with solid tumors including a varied genetic signature, complex molecular signaling pathways, defective cross talk between the tumor cells and immune cells, hypoxic and immunosuppressive effects of tumor microenvironment result in a treatment resistant and metastatic phenotype. Over the past several years, immunotherapy has emerged as an attractive therapeutic option against multiple malignancies. The unique ability of natural killer (NK) cells to target cancer cells without antigen specificity makes them an ideal candidate for use against solid tumors. However, the outcomes of adoptive NK cell infusions into patients with solid tumors have been disappointing. Extensive studies have been done to investigate different strategies to improve the NK cell function, trafficking and tumor targeting. Use of cytokines and cytokine analogs has been well described and utilized to enhance the proliferation, stimulation and persistence of NK cells. Other techniques like blocking the human leukocyte antigen-killer cell receptors (KIR) interactions with anti-KIR monoclonal antibodies, preventing CD16 receptor shedding, increasing the expression of activating NK cell receptors like NKG2D, and use of immunocytokines and immune checkpoint inhibitors can enhance NK cell mediated cytotoxicity. Using genetically modified NK cells with chimeric antigen receptors and bispecific and trispecific NK cell engagers, NK cells can be effectively redirected to the tumor cells improving their cytotoxic potential. In this review, we have described these strategies and highlighted the need to further optimize these strategies to improve the clinical outcome of NK cell based immunotherapy against solid tumors.

Biological activities of interleukin (IL)-21 in human monocytes and macrophages

The biological roles of interleukin (IL)-21 in human monocytes and macrophages have been neglected. We previously demonstrated that IL-21 induce phagocytosis and established that Syk is a new molecular target of IL-21. Herein, we found that IL-21 is not chemoattractant for immature THP-1 and primary monocytes but can increase the capacity of THP-1 cells (not primary monocytes) to adhere onto a cell substratum by a Syk-dependent mechanism without altering the expression of a panel of cell surface molecules. Unlike THP- 1 and monocytes, IL-21 can increase metalloproteinase (MMP)-9 secretion and activity in monocyte-derived macrophages (HMDM), as assessed by western blot and zymography experiments, respectively. We reported that IL-21 did not increase the production of IL-6 and the chemokines MIP-1α and GRO-α in HMDM. Therefore, IL-21 can increase functions other that phagocytosis, but this cytokine does not have a large spectrum of biological activities in monocytes and macrophages.

IL-21-mediated expansion of Vγ9Vδ2 T cells is limited by the Tim-3 pathway

Vγ9Vδ2 T cells are the main γδ T subset in the peripheral blood and lymphoid organs. Previous studies have shown that Vγ9Vδ2 T cells could expand in the presence of phosphoantigens and IL-2 and exert antitumor functions. However, their potency was limited because sustained proliferation could not be achieved, possibly due to exhaustion caused by prolonged antigenic stimulation. In this study, we examined the proliferative response of Vγ9Vδ2 T cells to IL-21, a cytokine previously shown to promote NK cell and CD8 T cell cytotoxicity. We found that IL-21 could significantly improve the proliferation of phosphoantigen-stimulated Vγ9Vδ2 T cells in a dose-dependent manner. However, in acute myeloid leukemia (AML) patients, the efficacy of IL-21 was significantly reduced. Vγ9Vδ2 T cells from AML patients exhibited lower expression of IL-21R, and required higher levels of IL-21 for expansion. IL-21-treated Vγ9Vδ2 T cells from AML patients presented lower increase in STAT1 phosphorylation than Vγ9Vδ2 T cells from healthy volunteers. Interestingly, AML Vγ9Vδ2 T cells presented significantly higher Tim-3 expression than healthy Vγ9Vδ2 T cells. IL-21 treatment further induced Tim-3 upregulation. Blocking Tim-3 increased the proliferation and the STAT phosphorylation in Vγ9Vδ2 T cells in response to IL-21. Together, these results demonstrated that IL-21 could significantly expand the Vγ9Vδ2 T cells, but its efficacy was limited since it also increased the expression of checkpoint molecule Tim-3.

Discovery and characterization of potent IL-21 neutralizing antibodies via a novel alternating antigen immunization and humanization strategy

Interleukin-21 (IL-21), a member of the common cytokine receptor γ chain (γc) family, is secreted by CD4+ T cells and natural killer T cells and induces effector function through interactions with the IL-21 receptor (IL-21R)/γc complex expressed on both immune and non-immune cells. Numerous studies suggest that IL-21 plays a significant role in autoimmune disorders. Therapeutic intervention to disrupt the IL-21/IL-21R/γc interaction and inhibit subsequent downstream signal transduction could offer a treatment paradigm for these diseases. Potent neutralizing antibodies reported in the literature were generated after extensive immunizations with human IL-21 alone and in combination with various adjuvants. To circumvent the laborious method of antibody generation while targeting a conserved functional epitope, we designed a novel alternating-antigen immunization strategy utilizing both human and cynomolgus monkey (cyno) IL-21. Despite the high degree of homology between human and cyno IL-21, our alternating-immunization strategy elicited higher antibody titers and more potent neutralizing hybridomas in mice than did the immunization with human IL-21 antigen alone. The lead hybridoma clone was humanized by grafting the murine complementarity-determining regions onto human germline framework templates, using a unique rational design. The final humanized and engineered antibody, MEDI7169, encodes only one murine residue at the variable heavy/light-chain interface, retains the sub-picomolar affinity for IL-21, specifically inhibits IL-21/IL-21R-mediated signaling events and is currently under clinical development as a potential therapeutic agent for autoimmune diseases. This study provides experimental evidence of the immune system's potential to recognize and respond to shared epitopes of antigens from distinct species, and presents a generally applicable, novel method for the rapid generation of exceptional therapeutic antibodies using the hybridoma platform.

Recurrent Stimulation of Natural Killer Cell Clones with K562 Expressing Membrane-Bound Interleukin-21 Affects Their Phenotype, Interferon-γ Production, and Lifespan

A pattern of natural killer cell (NK cell) heterogeneity determines proliferative and functional responses to activating stimuli in individuals. Obtaining the progeny of a single cell by cloning the original population is one of the ways to study NK cell heterogeneity. In this work, we sorted single cells into a plate and stimulated them via interleukin (IL)-2 and gene-modified K562 feeder cells that expressed membrane-bound IL-21 (K562-mbIL21), which led to a generation of phenotypically confirmed and functionally active NK cell clones. Next, we applied two models of clone cultivation, which differently affected their phenotype, lifespan, and functional activity. The first model, which included weekly restimulation of clones with K562-mbIL21 and IL-2, resulted in the generation of relatively short-lived (5⁻7 weeks) clones of highly activated NK cells. Levels of human leukocyte antigen class II molecule-DR isotype (HLA-DR) expression in the expanded NK cells correlated strongly with interferon-γ (IFN-γ) production. The second model, in which NK cells were restimulated weekly with IL-2 alone and once on the sixth week with K562-mbIL21 and IL-2, produced long-lived clones (8⁻14 weeks) that expanded up to 10⁷ cells with a lower ability to produce IFN-γ. Our method is applicable for studying variability in phenotype, proliferative, and functional activity of certain NK cell progeny in response to the stimulation, which may help in selecting NK cells best suited for clinical use.

Structural Basis for Signaling Through Shared Common γ Chain Cytokines

The common γ chain (γ_c) family of hematopoietic cytokines consists of six distinct four α-helix bundle soluble ligands that signal through receptors which include the shared γ_c subunit to coordinate a wide range of physiological processes, in particular, those related to innate and adaptive immune function. Since the first crystallographic structure of a γ_c family cytokine/receptor signaling complex (the active Interleukin-2 [IL-2] quaternary complex) was determined in 2005 [1], tremendous progress has been made in the structural characterization of this protein family, transforming our understanding of the molecular mechanisms underlying immune activity. Although many conserved features of γ_c family cytokine complex architecture have emerged, distinguishing details have been observed for individual cytokine complexes that rationalize their unique functional properties. Much work remains to be done in the molecular characterization of γ_c family signaling, particularly with regard to intracellular activation events, and looking forward, new technologies in structural biophysics will offer further insight into the biology of cytokine signaling to inform the design of targeted therapeutics for treatment of immune-linked diseases such as cancer, infection, and autoimmune disorders.

Upregulated Interleukin 21 Receptor Enhances Proliferation and Epithelial-Mesenchymal Transition Process in Benign Prostatic Hyperplasia

Background: Interleukins (ILs) and related chronic inflammation have been found to contribute to the development of benign prostatic hyperplasia (BPH) in recent decades. As a late member of the ILs family, IL-21 receptor (IL-21R) can modulate cell proliferation, however, IL-21R activity in the prostate has not been examined. The current study aimed to elucidate a potential role of IL-21R in the development of BPH. Material and Methods: Human prostate tissues, cell lines and rats were used. QRT-PCR, Western blot, and immunohistochemistry, along with hematoxylin and eosin, Masson's trichrome, and immunofluorescent staining were performed. BPH-1 cells with IL-21R silenced were cultured or co-cultured with macrophages (active THP-1, AcTHP-1). Apoptosis and cell cycle phases were determined via flow cytometry. Epithelial-mesenchymal transition (EMT) processes were also examined. In vivo, rat prostatitis was induced with intraprostatic injected lipopolysaccharide (LPS). Results: IL-21R was highly expressed in human as well as rat prostate, mainly in the epithelial compartment. BPH concomitant with prostatitis significantly upregulated the expression of IL-21R. Knockdown of IL-21R induced cell apoptosis and cycle arrest at G0/G1 phase, and blocked the EMT process in BPH-1 cells. When IL-21R silenced BPH-1 cells were co-cultured with AcTHP-1 cells, these aforementioned processes and IL-21R change were completely reversed. Prostatic hyperplasia was observed with IL-21R upregulated in LPS induced prostatitis rats. More specifically, the expression of apoptosis, cyclin, and EMT proteins in this rat model are altered in a manner consistent with that seen in the cell line model. Conclusions: Our novel data demonstrates the expression and functional activities of IL-21R in the mechanism for development of BPH. IL-21R mainly localized in prostate epithelium and it was upregulated in hyperplastic prostate tissues. IL-21R enhanced proliferation of BPH-1 cells, via inhibiting cell apoptosis, and modulating cell cycles, as well as the EMT process, in response to inflammatory stimuli.

Transient Expression of Interleukin-21 in the Second Hit of Acute Pancreatitis May Potentiate Immune Paresis in Severe Acute Pancreatitis

OBJECTIVES

Interleukin-21 (IL-21) is a cytokine associated with tissue inflammation, autoimmune and infectious diseases. Organ dysfunction and death can occur in patients with acute pancreatitis (AP) in two distinct clinical phases. Initially, a systemic inflammatory response syndrome may be followed by systemic sepsis from infected pancreatic necrosis, known as the "second hit." The expression and possible role of IL-21 in AP has not been established.

METHODS

Thirty-six patients with mild, moderate, and severe AP (SAP) were enrolled. Peripheral blood samples of patients were drawn on days 7, 9, 11, and 13. Reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay were performed to determine the expression and concentration of IL-21.

RESULTS

Interleukin-21 mRNA levels increased significantly at day 9 in severe (P = 0.002) pancreatitis compared with both the mild and control patient groups. At the protein level, IL-21 was elevated in SAP patients compared with those with mild pancreatitis, although this was not significant. Furthermore, day 9 IL-21 was elevated in septic SAP patients and patients with pancreatic necrosis.

CONCLUSIONS

Interleukin-21 is transiently elevated in SAP compared with the mild/moderate group, and hence IL-21 may contribute to the immune imbalance that occurs in AP.

NK Cell-Based Immunotherapy in Cancer Metastasis

Metastasis represents the leading cause of cancer-related death mainly owing to the limited efficacy of current anticancer therapies on advanced malignancies. Although immunotherapy is rendering promising results in the treatment of cancer, many adverse events and factors hampering therapeutic efficacy, especially in solid tumors and metastases, still need to be solved. Moreover, immunotherapeutic strategies have mainly focused on modulating the activity of T cells, while Natural Killer (NK) cells have only recently been taken into consideration. NK cells represent an attractive target for cancer immunotherapy owing to their innate capacity to eliminate malignant tumors in a non-Major Histocompatibility Complex (MHC) and non-tumor antigen-restricted manner. In this review, we analyze the mechanisms and efficacy of NK cells in the control of metastasis and we detail the immunosubversive strategies developed by metastatic cells to evade NK cell-mediated immunosurveillance. We also share current and cutting-edge clinical approaches aimed at unleashing the full anti-metastatic potential of NK cells, including the adoptive transfer of NK cells, boosting of NK cell activity, redirecting NK cell activity against metastatic cells and the release of evasion mechanisms dampening NK cell immunosurveillance.

Measurement of IL-21 in human serum and plasma using ultrasensitive MSD S-PLEX® and Quanterix SiMoA methodologies

IL-21 is a pleiotropic cytokine that plays a key role in modulating inflammatory responses, including the promotion of autoimmune diseases. Several groups have quantitated circulating levels of IL-21 in plasma and serum samples using various commercial ELISAs. We determined, however, that the most commonly used commercial assays in published literature were not specific or sensitive enough to detect levels of IL-21 in heparin plasma or serum from healthy human individuals. This finding prompted an effort to develop more specific and sensitive methods to quantitate IL-21 in complex biological matrices using proprietary anti-IL-21 antibodies with the Quanterix SiMoA platform and the Meso Scale Discovery (MSD) S-PLEX® format. Assays developed on both technology platforms were characterized in heparin plasma and serum using spike recoveries across a range of concentrations. Each method was able to detect sub-pg/mL levels of IL-21 (predicted Limit of Detection [LOD] of approximately 1.0 fg/mL for both the Quanterix SiMoA and MSD S-PLEX® platforms) which is 200-500 times lower than current commercial assays. Additionally we demonstrated that rheumatoid factor did not interfere with measuring IL-21 in the Quanterix SiMoA assay. Results obtained with the two new ultrasensitive assays showed a strong correlation (r = 0.9428; p < .0001). Additionally, IL-21 levels were significantly increased in samples from patients with Systemic Lupus Erythematosus (mean+/- SD: n = 14, 202.64 +/- 111.47 fg/mL, p = .0001 for Quanterix SiMoA and 275.4 +/- 174.66 fg/mL p = .0001 for MSD S-PLEX®) as well as in samples from patients with Sjögren's Syndrome (mean+/- SD: n = 11, 122.18 +/- 84.50 fg/mL, p = .0029 for Quanterix SiMoA and 183.64 +/- 153.00 fg/mL, p = .0082 for MSD S-PLEX®) when compared to healthy donors (mean+/- SD: n = 11, 38.1 +/- 27.8 fg/mL for Quanterix SiMoA and 58.1 +/- 30.7 fg/mL for MSD S-PLEX®). These ultrasensitive assays, for the first time, allow for the accurate quantitation of human IL-21 in heparin plasma and serum. In addition, these experiments also provide a direct comparison of the MSD S-PLEX® format and Quanterix SiMoA platform technologies, which may have broader implications to future application of these methods to evaluate low abundance proteins in complex biological matrices.

Analysis of NK cell clones obtained using interleukin-2 and gene-modified K562 cells revealed the ability of "senescent" NK cells to lose CD57 expression and start expressing NKG2A

In this work, we analyzed the phenotype and growth of human NK cell clones obtained by the stimulation of individual NK cells with IL-2 and gene-modified K562 feeder cells expressing membrane-bound IL-21 (K562-mbIL21). We generated clones from NK cells at distinct differentiation and activation stages, determined by CD56, CD57 and HLA-DR expression levels. Less differentiated CD56^bright NK cell subsets showed higher cloning efficiency compared with more differentiated CD56^dim subsets, especially with the CD57^bright subset. However, clones from the CD56^dimCD57^– subset lived longer on average than other subsets. Moreover, several clones with the highest cell numbers were derived from CD56^dimCD57^–HLA-DR⁻cells. Most of the clones including those derived from more differentiated CD56^dimCD57^+/–NKG2A^– NK cells showed a less-differentiated NKG2A⁺ phenotype. Also, CD57^– cells were frequently observed in clones derived from CD57⁺ NK cells suggesting the loss of CD57 during the cloning process. On the other hand, KIR surface expression once detected for a clone never disappeared entirely, confirming irreversibility of the KIR expression. In summary, we have demonstrated that in specific conditions terminally differentiated CD57⁺ human NK cells are able to acquire the CD57^– phenotype that was previously not observed and, thus, was considered impossible.

Noninvasive profiling of serum cytokines in breast cancer patients and clinicopathological characteristics

Cancers elicit an immune response by modifying the microenvironment. The immune system plays a pivotal role in cancer recognition and eradication. While the potential clinical value of infiltrating lymphocytes at the tumor site has been assessed in breast cancer, circulating cytokines – the molecules coordinating and fine-tuning immune response – are still poorly characterized.

Using two breast cancer cohorts (MicMa, n = 131, DCTB, n = 28) and the multiplex Luminex platform, we measured the levels of 27 cytokines in the serum of breast cancer patients prior to treatment. We investigated the cytokine levels in relation to clinicopathological characteristics and in perspective of the tumor infiltrating immune cells predicted from the bulk mRNA expression data.

Unsupervised clustering analysis of the serum cytokine levels in the MicMa cohort identified a cluster of pro-inflammatory, pro-angiogenic, and Th2-related cytokines which was associated with poor prognosis. Notably high levels of platelet derived growth factor BB (PDGF) reflected a more aggressive tumor phenotype and larger tumor size. A significant positive correlation between serum levels of interferon gamma-induced protein 10 (IP10) and its mRNA expression at the tumor site suggested that tumor-IP10-production may outflow to the bloodstream. High IP10 serum levels were associated with a worse prognosis. Finally, we found serum levels of both PDGF and IP10 associated with enrichment scores of specific tumor infiltrating immune cells.

Our study suggests that monitoring cytokine circulating levels in breast cancer could be used to characterize breast cancers and the immune composition of their microenvironment through readily available biological material.

IL-21 receptor signaling is essential for control of hepatocellular carcinoma growth and immunological memory for tumor challenge

Hepatocellular carcinoma (HCC) is a typical inflammation-associated cancer. IL-21 regulates both innate and adaptive immune responses and has key roles in antitumor and antiviral responses. However, the role of IL-21 in HCC development is poorly defined. In the current study, we explored the role of IL-21R signaling in HCC growth by using IL-21R knockout mice and HCC mouse models. We discovered that IL-21R signaling deficiency promoted HCC growth in tumor-bearing mice. We showed that IL-21R deletion reduced T cells infiltration and activation as well as their function but increased the accumulation of myeloid-derived suppressor cells in tumor tissues to enhance HCC growth. Furthermore, loss of IL-21R signaling in tumor-bearing mice resulted in an imbalance of the systemic immune system characterized by decreased antitumor immune cells and increased immunosuppressive cells in the spleen and lymph nodes. In addition, we revealed that IL-21R signaling is critical for the expansion of antitumor immune cells in the memory immune response to tumor rechallenge. Finally, we showed that the transcriptional levels of IL-21 in the peritumoral region and IL-21R within the tumor are associated with survival and recurrence of HCC patients. In conclusion, our study demonstrates that IL-21R signaling is essential for controlling the development of HCC and immunological memory response to tumor challenge.

T follicular helper cells restricted by IRF8 contribute to T cell-mediated inflammation

The follicular helper T cell (T_FH) are established regulators of germinal center (GC) B cells, whether T_FH have pathogenic potential independent of B cells is unknown. Based on in vitro T_FH cell differentiation, in vivo T cell transfer animal colitis model, and intestinal tissues of inflammatory bowel disease (IBD) patients, T_FH and its functions in colitis development were analyzed by FACS, ChIP, ChIP-sequencing, WB, ELISA and PCR. Herein we demonstrate that intestinal tissues of patients and colon tissues obtained from Rag1^-/- recipients of naïve CD4⁺ T cells with colitis, each over-express T_FH-associated gene products. Adoptive transfer of naïve Bcl6^-/- CD4⁺ T cells into Rag1^-/- recipient mice abrogated development of colitis and limited T_FH differentiation in vivo, demonstrating a mechanistic link. In contrast, T cell deficiency of interferon regulatory factor 8 (IRF8) resulted in augmentation of T_FH induction in vitro and in vivo. Functional studies showed that adoptive transfer of IRF8 deficient CD4⁺ T cells into Rag1^-/- recipients exacerbated colitis development associated with increased gut T_FH-related gene expression, while Irf8^-/-/Bcl6^-/- CD4⁺ T cells abrogated colitis, together indicating that IRF8-regulated T_FH can directly cause colon inflammation. Molecular analyses revealed that IRF8 suppresses T_FH differentiation by inhibiting transcription and transactivation of the TF IRF4, which is also known to be essential for T_FH induction. Our documentation showed that IRF8-regulated T_FH can function as B-cell-independent, pathogenic, mediators of colitis suggests that targeting T_FH could be effective for treatment of IBD.

The Common Cytokine Receptor γ Chain Family of Cytokines

Interleukin (IL)-2, IL-4, IL-7, IL-9, IL-15, and IL-21 form a family of cytokines based on their sharing the common cytokine receptor γ chain (γc), which was originally discovered as the third receptor component of the IL-2 receptor, IL-2Rγ. The IL2RG gene is located on the X chromosome and is mutated in humans with X-linked severe combined immunodeficiency (XSCID). The breadth of the defects in XSCID could not be explained solely by defects in IL-2 signaling, and it is now clear that γc is a shared receptor component of the six cytokines noted above, making XSCID a disease of defective cytokine signaling. Janus kinase (JAK)3 associates with γc, and JAK3-deficient SCID phenocopies XSCID, findings that served to stimulate the development of JAK3 inhibitors as immunosuppressants. γc family cytokines collectively control broad aspects of lymphocyte development, growth, differentiation, and survival, and these cytokines are clinically important, related to allergic and autoimmune diseases and cancer as well as immunodeficiency. In this review, we discuss the actions of these cytokines, their critical biological roles and signaling pathways, focusing mainly on JAK/STAT (signal transducers and activators of transcription) signaling, and how this information is now being used in clinical therapeutic efforts.

T Cell/B Cell Collaboration and Autoimmunity: An Intimate Relationship

Co-ordinated interaction between distinct cell types is a hallmark of successful immune function. A striking example of this is the carefully orchestrated cooperation between helper T cells and B cells that occurs during the initiation and fine-tuning of T-cell dependent antibody responses. While these processes have evolved to permit rapid immune defense against infection, it is becoming increasingly clear that such interactions can also underpin the development of autoimmunity. Here we discuss a selection of cellular and molecular pathways that mediate T cell/B cell collaboration and highlight how in vivo models and genome wide association studies link them with autoimmune disease. In particular, we emphasize how CTLA-4-mediated regulation of CD28 signaling controls the engagement of secondary costimulatory pathways such as ICOS and OX40, and profoundly influences the capacity of T cells to provide B cell help. While our molecular understanding of the co-operation between T cells and B cells derives from analysis of secondary lymphoid tissues, emerging evidence suggests that subtly different rules may govern the interaction of T and B cells at ectopic sites during autoimmune inflammation. Accordingly, the phenotype of the T cells providing help at these sites includes notable distinctions, despite sharing core features with T cells imparting help in secondary lymphoid tissues. Finally, we highlight the interdependence of T cell and B cell responses and suggest that a significant beneficial impact of B cell depletion in autoimmune settings may be its detrimental effect on T cells engaged in molecular conversation with B cells.

Serum cytokine levels in breast cancer patients during neoadjuvant treatment with bevacizumab

A high concentration of circulating vascular endothelial growth factor (VEGF) in cancer patients is associated with an aggressive tumor phenotype. Here, serum levels of 27 cytokines and blood cell counts were assessed in breast cancer patients receiving neoadjuvant chemotherapy with or without bevacizumab (Bev) in a randomized cohort of 132 patients with non-metastatic HER2-negative tumors. Cytokine levels were determined prior to treatment and at various time-points. The cytotoxic chemotherapy regimen of fluorouracil, epirubicin, and cyclophosphamide (FEC) had a profound impact on both circulating white blood cells and circulating cytokine levels. At the end of FEC treatment, the global decrease in cytokine levels correlated with the drop in white blood cell counts and was significantly greater in the patients of the Bev arm for cytokines, such as VEGF-A, IL-12, IP-10 and IL-10. Among patients who received Bev, those with pathological complete response (pCR) exhibited significantly lower levels of VEGF-A, IFN-γ, TNF-α and IL-4 than patients without pCR. This effect was not observed in the chemotherapy-only arm. Certain circulating cytokine profiles were found to correlate with different immune cell types at the tumor site. For the Bev arm patients, the serum cytokine levels correlated with higher levels of cytotoxic T cells at the end of the therapy regimen, which was indicative of treatment response. The higher response rate for Bev-treated patients and stronger correlations between serum cytokine levels and infiltrating CD8T cells merits further investigation.

TH17-Induced Neutrophils Enhance the Pulmonary Allergic Response Following BALB/c Exposure to House Dust Mite Allergen and Fine Particulate Matter From California and China

Asthma is a global and increasingly prevalent disease. According to the World Health Organization, approximately 235 million people suffer from asthma. Studies suggest that fine particulate matter (PM2.5) can induce innate immune responses, promote allergic sensitization, and exacerbate asthmatic symptoms and airway hyper-responsiveness. Recently, severe asthma and allergic sensitization have been associated with T-helper cell type 17 (TH17) activation. Few studies have investigated the links between PM2.5 exposure, allergic sensitization, asthma, and TH17 activation. This study aimed to determine whether (1) low-dose extracts of PM2.5 from California (PMCA) or China (PMCH) enhance allergic sensitization in mice following exposure to house dust mite (HDM) allergen; (2) eosinophilic or neutrophilic inflammatory responses result from PM and HDM exposure; and (3) TH17-associated cytokines are increased in the lung following exposure to PM and/or HDM. Ten-week-old male BALB/c mice (n = 6-10/group) were intranasally instilled with phosphate-buffered saline (PBS), PM+PBS, HDM, or PM+HDM, on days 1, 3, and 5 (sensitization experiments), and PBS or HDM on days 12-14 (challenge experiments). Pulmonary function, bronchoalveolar lavage cell differentials, plasma immunoglobulin (Ig) protein levels, and lung tissue pathology, cyto-/chemo-kine proteins, and gene expression were assessed on day 15. Results indicated low-dose PM2.5 extracts can enhance allergic sensitization and TH17-associated responses. Although PMCA+HDM significantly decreased pulmonary function, and significantly increased neutrophils, Igs, and TH17-related protein and gene levels compared with HDM, there were no significant differences between HDM and PMCH+HDM treatments. This may result from greater copper and oxidized organic content in PMCA versus PMCH.

Interleukin-21 Induces Short-Lived Effector CD8+ T Cells but Does Not Inhibit Their Exhaustion after Mycobacterium bovis BCG Infection in Mice

Interleukin 21 (IL-21) is a pleiotropic common cytokine receptor γ chain cytokine that promotes the effector functions of NK cells and CD8⁺ T cells and inhibits CD8⁺ T cell exhaustion during chronic infection. We found that the absolute number of short-lived effector CD8⁺ T cells (SLECs) (KLRG1^high CD127^low) decreased significantly in IL-21 receptor-deficient (IL-21R^-/-) mice during Mycobacterium bovis bacillus Calmette-Guérin (BCG) infection. Early effector CD8⁺ T cells (EECs) (KLRG1^low CD127^low) were normally generated in IL-21R^-/- mice after infection. Exhausted CD8⁺ T cells (PD-1^high KLRG1^low) were also normally generated in IL-21R^-/- mice after infection. Mixed bone marrow (BM) chimera and transfer experiments showed that IL-21R on CD8⁺ T cells was essential for the proliferation of EECs, allowing them to differentiate into SLECs after BCG infection. On the other hand, the number of SLECs increased significantly after infection with recombinant BCG (rBCG) that secreted an antigen 85B (Ag85B)-IL-21 fusion protein (rBCG-Ag85B-IL-21), but the number of exhausted CD8⁺ T cells did not change after rBCG-Ag85B-IL-21 infection. These results suggest that IL-21 signaling drives the differentiation of SLECs from EECs but does not inhibit the exhaustion of CD8⁺ T cells following BCG infection in mice.

Under-Evaluated or Unassessed Pathogenic Pathways in Autoimmune Hepatitis and Implications for Future Management

Autoimmune hepatitis is a consequence of perturbations in homeostatic mechanisms that maintain self-tolerance but are incompletely understood. The goals of this review are to describe key pathogenic pathways that have been under-evaluated or unassessed in autoimmune hepatitis, describe insights that may shape future therapies, and encourage investigational efforts. The T cell immunoglobulin mucin proteins constitute a family that modulates immune tolerance by limiting the survival of immune effector cells, clearing apoptotic bodies, and expanding the population of granulocytic myeloid-derived suppressor cells. Galectins influence immune cell migration, activation, proliferation, and survival, and T cell exhaustion can be induced and exploited as a possible management strategy. The programmed cell death-1 protein and its ligands comprise an antigen-independent inhibitory axis that can limit the performance of activated T cells by altering their metabolism, and epigenetic changes can silence pro-inflammatory genes or de-repress anti-inflammatory genes that affect disease severity. Changes in the intestinal microbiota and permeability of the intestinal mucosal barrier can be causative or consequential events that affect the occurrence and phenotype of immune-mediated disease, and they may help explain the female propensity for autoimmune hepatitis. Perturbations within these homeostatic mechanisms have been implicated in experimental models and limited clinical experiences, and they have been favorably manipulated by monoclonal antibodies, recombinant molecules, pharmacological agents or dietary supplements. In conclusion, pathogenic mechanisms that have been implicated in other systemic immune-mediated and liver diseases but under-evaluated or unassessed in autoimmune hepatitis warrant consideration and rigorous evaluation.

Model of the adaptive immune response system against HCV infection reveals potential immunomodulatory agents for combination therapy

A regulated immune system employs multiple cell types, diverse variety of cytokines and interacting signalling networks against infections. Systems biology offers a promising solution to model and simulate such large populations of interacting components of immune systems holistically. This study focuses on the distinct components of the adaptive immune system and analysis, both individually and in association with HCV infection. The effective and failed adaptive immune response models have been developed followed by interventions/perturbations of various treatment strategies to get better assessment of the treatment responses under varying stimuli. Based on the model predictions, the NK cells, T regulatory cells, IL-10, IL-21, IL-12, IL-2 entities are found to be the most critical determinants of treatment response. The proposed potential immunomodulatory therapeutic interventions include IL-21 treatment, blocking of inhibitory receptors on T-cells and exogenous anti-IL-10 antibody treatment. The relative results showed that these interventions have differential effect on the expression levels of cellular and cytokines entities of the immune response. Notably, IL-21 enhances the expression of NK cells, Cytotoxic T lymphocytes and CD4+ T cells and hence restore the host immune potential. The models presented here provide a starting point for cost-effective analysis and more comprehensive modeling of biological phenomenon.

Role of interleukin-21 and interleukin-21 receptor polymorphisms in the treatment of HBeAg-positive chronic hepatitis B patients with peginterferon

The aim of this study was to evaluate the relationship between interleukin-21 (IL-21) and interleukin-21 receptor (IL-21R) polymorphisms and the response to peginterferon alfa (PEG-IFN α) therapy in HBeAg-positive chronic hepatitis B (CHB) patients.A total of 143 HBeAg-positive CHB patients treated for 48 weeks with PEG-IFN α and followed up for 24 weeks post-treatment were retrospectively evaluated. Genotypes analysis was performed for IL-21 polymorphisms rs907715, rs2221903, and IL-21R polymorphisms rs3093301 and rs2285452. Serum IL-21 levels were measured by enzyme-linked immunosorbent assay.The end of virological response (EVR) rate was 46.9% (67/143) at the end of treatment, the sustained virological response (SVR) rate was 43.4% (62/143) and the complete response (CR) rate was 32.1% (46/143) at 24 weeks post-treatment. Patients who carried IL-21 rs 2221903 genotype AA had a rather higher rate of EVR (response rate: 52.4%, odds ratio [OR] 0.42, 95% confidence interval [CI]: 0.19-0.91, P = .021), SVR (response rate: 47.6%, OR 0.43, 95% CI: 0.19-0.95, P = .028), and CR (response rate: 38.1%, OR 0.31, 95% CI: 0.12-0.79, P = .014) when compared to those had AG genotype. Meanwhile, IL-21rs 2221903 genotype AA was also independently associated with markedly reduced HBsAg levels (>1og10 IU/mL) after 24 weeks treatment and low HBsAg levels (<100 IU/mL) at the end of treatment. IL-21 rs907715 AG/GG genotype was independently associated with SVR (OR: 2.92, 95% CI: 0.98-8.6, P = .039; OR: 3.23, 95% CI: 1.0-10.4, P = .039). Patients with IL-21 rs907715 AG/GG genotype had higher serum IL-21 levels than those with rs907715 AA genotype (P = .021).IL-21 rs2221903 and rs907715 polymorphisms were significantly associated with the treatment response to PEG-IFN α among Chinese HBeAg-positive CHB patients.

Neutralizing FGF4 protein in conditioned medium of IL-21-silenced HCT116 cells restores the migratory activity of the colorectal cancer cells

The interleukin-21 (IL-21) protein was found to be expressed at an elevated level in clinical samples of colorectal cancer patients without or with a parasitic infection that were collected from Sudan in our previous study. The IL-21 gene in HT29 and HCT116 cells was then correlated to cell proliferation and cell migration, as well as the cellular mechanisms associated with gene expressions in our present study. Our results demonstrated that silencing the IL-21 gene in HCT116 cells increased the cytotoxic level and fibroblast growth factor-4 (FGF4) mRNA expression in the cancer cells. Moreover, specific gene silencing reduced the migration of cancer cells compared to non-silenced cancer cells. These events were not observed in IL-21-silenced HT29 cells. Neutralizing FGF4 in conditioned medium of IL-21-silenced HCT116 cells further increased the cytotoxic level and restored the migratory activity of HCT116 cells in the culture compared to silencing the IL-21 gene alone in the cancer cells. Our results indicate the importance of both silencing the IL-21 gene and co-expression of the FGF4 protein in HCT116 cells, which pave the way for the discovery of important factors to be used as biomarkers for the design of drugs or cost-effective supplements to effectively treat the patients having infectious disease and HCT116 cells of colorectal cancer simultaneously in the future.

IL-21 alleviates allergic asthma in DOCK8-knockout mice

Patients with DOCK8 deficiency are at increased susceptibility to develop allergic diseases such as food allergy and asthma. Here, we aimed to analyze the pathogenesis of asthma in DOCK8-deficient patients. In our mouse model, DOCK8-knockout (KO) mice sensitized with low-dose OVA were challenged with 1.5% OVA to induce allergic asthma. As compared to that in WT mice, remarkable airway hyperresponsiveness was observed in KO mice. Increased inflammatory cells and eosinophils infiltrated in airway lumen in KO mice especially around bronchi. KO mice showed higher levels of serum IgE and OVA-specific IgE and significantly elevated IgE-producing B cells in blood and in spleen. Surprisingly, nasal administration with rmIL-21 significantly reduced the airway hyperresponsiveness, inflammatory infiltration, as well as the serum IgE and IgE-producing B cells. DOCK8-knockout mice are susceptible to low-dose OVA induced allergic airway inflammation and airway hyperresponsiveness. Supplementary nasal administration of rmIL-21 alleviates allergic asthma in this mouse model.

Synergistic antitumor effect of polysaccharide from Lachnum sp. in combination with cyclophosphamide in hepatocellular carcinoma

Combination therapy with chemotherapeutics is attracting increasing attention as an important treatment option for hepatocellular carcinoma (HCC) due to its complex pathological characteristics. In this study, as a new therapy strategy, combination treatment of LEP-2a (a non-toxic polysaccharide from Lachnum sp.) with cyclophosphamide (CTX) was investigated. Results showed that combination treatment with LEP-2a and CTX processed a significantly synergistic anti-tumor effect in H22 tumor-bearing mice through Fas/FasL mediated caspase-dependent death pathway and mitochondria apoptosis pathway. Moreover, our study indicated that LEP-2a played a crucial role in enhancement of immune response, inhibition of tumor angiogenesis and down-regulation of survival associated proteins. Notably, side effects induced by CTX were relieved after LEP-2a treatment. These results support the conception that LEP-2a has the potential as an ideal adjuvant agent for a more effective combination therapy with CTX against HCC.

IL-21 drives expansion and plasma cell differentiation of autoreactive CD11chiT-bet+ B cells in SLE

Although the aetiology of systemic lupus erythematosus (SLE) is unclear, dysregulated B cell responses have been implicated. Here we show that an unusual CD11c^hiT-bet⁺ B cell subset, with a unique expression profile including chemokine receptors consistent with migration to target tissues, is expanded in SLE patients, present in nephrotic kidney, enriched for autoreactive specificities and correlates with defined clinical manifestations. IL-21 can potently induce CD11c^hiT-bet⁺ B cells and promote the differentiation of these cells into Ig-secreting autoreactive plasma cells. While murine studies have identified a role for T-bet-expressing B cells in autoimmunity, this study describes and exemplifies the importance of CD11c^hiT-bet⁺ B cells in human SLE.

Systemic lupus erythematosus (SLE) is associated with altered B cell responses but the underlying aetiology is still unclear. Here the authors show that a CD11c^hiT-bet⁺ B cell subset with a unique phenotype and transcriptome is increased in patients with SLE, can be expanded by IL-21, and may contribute to autoimmune responses in SLE.

NK Cell-derived Exosomes From NK Cells Previously Exposed to Neuroblastoma Cells Augment the Antitumor Activity of Cytokine-activated NK Cells

Immune cell-derived exosomes can increase immunity against tumors. In contrast, tumor-derived exosomes can reduce the immunity and can change the tumor microenvironment to further develop and provide metastasis. These effects take place by an alteration in the innate and adaptive immune cell functions. In this experiment, we studied the natural killer (NK) cells' effectiveness on tumor cells after expansion and thereafter incubated it with exosomes. The exosomes were derived from 2 populations of NK cells: (1) naive NK cells and, (2) NK cells previously exposed to neuroblastoma (NB) cells. Moreover, we have studied the NB-derived exosomes on NK cell function. The molecular load of the characterized exosomes (by means of nanoparticle-tracking analysis, flow cytometry, scanning electron microscopy, and western blot) from NK cells exposed to the NB cell revealed their expression of natural killer cell receptors in addition to CD56, NKG2D, and KIR2DL2 receptors. These exosomes were used to treat NK cells and thereafter administered to NB tumor cells both in vitro and in vivo. Our results showed some kind of NK cells' education by the exosomes. This education from NK cells previously exposed to NB cell-derived exosomes caused efficient and greater cytotoxicity against NB tumors, but NB-derived exosomes act as tumor promoters by providing a tumor supporting niche. Hence, this method of preparing the exosomes has a dramatic effect on activation of anti-NK cells against NB cells.

Evaluating IL-21 as a Potential Therapeutic Target in Crohn's Disease

Background and Aim

Interleukin-21 (IL-21) is primarily a T cell-derived cytokine; it is upregulated in patients with Crohn's Disease (CD) and could be a potential new therapeutic target in CD.

Methods

In human material, IL-21 and IL-21R expression was investigated by in situ hybridization (ISH) and immunohistochemistry (IHC) in noninflammatory bowel disease (non-IBD) controls and patients with CD. The pathologic role of IL-21 was examined in murine models of T cell-dependent and T cell-independent colitis, either with a neutralizing monoclonal antibody against IL-21 or with the transfer of CD4⁺CD45RB^highIL-21R^-/- T cells. Colonic pathology was examined by endoscopy, histopathology, IHC, ELISA, and Luminex.

Results

In the human intestine, IL-21 and IL-21R mRNA and protein-expressing cells were observed in the mucosa, in lymphoid aggregates of submucosa in non-IBD controls, and in lymphoid aggregates of muscularis externa in patients with CD. IL-21 expression was most abundant in germinal centers (GCs) of the lymphoid aggregates, and IL-21R expression assessed semiquantitatively, was significantly higher in patients with CD compared to non-IBD controls. Following prophylactic and interventive anti-IL-21 mAb treatment in the adoptive transfer (AdTr) model, clinical and pathological parameters were significantly reduced. The most persistent finding was a reduction in colonic infiltrating neutrophils. As well, Rag2^-/- mice receiving CD4⁺CD45RB^highIL-21R^-/- T cells developed less severe colitis compared to Rag2^-/- mice receiving CD4⁺CD45RB^highIL-21R^+/+ T cells. No effect of reduced IL-21 signalling was observed in T cell-independent colitis.

Conclusion

Our study shows that patients with CD have significant expression of IL-21 and IL-21R in the gut. As well, we show that neutralization of IL-21 in experimental T cell-driven colitis is associated with a reduction in clinical and pathological findings. This amelioration seems to be associated with a reduction in colon-infiltrating neutrophils.

IL-21-secreting hUCMSCs combined with miR-200c inhibit tumor growth and metastasis via repression of Wnt/β-catenin signaling and epithelial-mesenchymal transition in epithelial ovarian cancer

Background

Epithelial ovarian cancer (EOC) with insidious characteristic manifests no symptoms in its early onset but most patients have advanced and distant cancer metastasis at diagnosis. Innovative early diagnosis and effective treatment of EOC are urgently needed.

Methods

In the study, we developed a novel agent of IL-21-secreting human umbilical cord mesenchymal stem cells (hUCMSCs) combined with miR-200c to evaluate its effects on SKOV3 EOC in vitro and in vivo.

Results

hUCMSCs-LV-IL-21 combined with miR-200c significantly inhibited the SKOV3 cell mobility and tumorigenesis compared with hUCMSCs-LV-IL-21, hUCMSCs-LV-vector, and hUCMSCs, respectively. These were reflected in decreasing the tumor sizes and elongating the tumor bearing nude mouse survival, accompanied with increasing the serum cytokine levels of IFN-γ, IL-21 and TNF-α as well as the splenocyte cytotoxicity. In addition, the expression of β-catenin, cyclin-D1, Gli1, Gli2, and ZEB1 was decreased but the E-cadherin expression was increased in tumor tissues of mice treated with hUCMSCs-LV-IL-21 plus miR-200c.

Conclusion

We demonstrated that the synergistic effect of fighting SKOV3 EOC is attributable to repression of Wnt/β-catenin signaling and epithelial-mesenchymal transition in SKOV3 EOC. The findings may provide a new strategy for therapy of EOC.

Impact of bone marrow-derived signals on NK cell development and functional maturation

Natural killer (NK) cells are cytotoxic members of type I innate lymphocytes (ILC1) with a prominent role in anti-tumor and anti-viral immune responses. Despite the increasing insight into NK cell biology, the steps and stages leading to mature circulating NK cells require further investigation. Natural killer cell development and functional maturation are complex and multi-stage processes that occur predominantly in the bone marrow (BM) and originate from haematopoietic stem cells CD34⁺ (HSC). Within the BM, NK cell precursor (NKP) and NK cell development intermediates reside in specialized niches that are characterized by particular cellular components that provide signals required for their maturation. These signals consist of soluble factors or direct cellular-contact interactions mediated by cytokines and growth factors with complementary, as well as overlapping roles in distinct developmental steps. Emerging evidence highlights the plasticity of the early phase of NK cell development, and the capacity of different signal combinations to redirect precursor lineage commitment through other innate cell populations. Here, we summarize the role of signals known to guide NK cell differentiation with a particular focus on the cytokines and the receptor/ligand pairs playing a critical role in these processes. A comprehensive understanding of the mechanisms underlying NK cell development will elucidate their roles in pathological conditions and will improve protocols for NK cell therapeutic application.

Effect of IL-18 on the Expansion and Phenotype of Human Natural Killer Cells: Application to Cancer Immunotherapy

When pathogenic stresses are recognized by innate immune cells, inflammasomes are assembled and caspase-1 is activated, resulting in the conversion of pro-IL-18 into mature IL-18. Because natural killer (NK) cells express IL-18 receptors, IL-18 may play roles in immune functions of NK cells. In the present study, we examined the effect of IL-18 on NK cells derived from lung cancer patients and healthy adult volunteers. When peripheral blood NK cells were stimulated with IL-2, the cells formed clusters beginning on day 5-6 and proliferated thereafter, in which the number of NK cells increased by 10-fold in 10 days. When IL-18 was added, cell clusters were observed as early as on day 4 and NK cells proliferated vigorously. On day 10, the expansion rate was 56-fold on average, showing that IL-18 promoted the expansion of NK cells. It was also notable that IL-18 enhanced the expression of CD80, CD86, HLA-DR and HLA-DQ on NK cells, suggesting that IL-18 conferred NK cells an APC-like phenotype. When cellular cytotoxicity was determined, APC-like NK cells efficiently killed tumor cells and anti-tumor activity was augmented by the addition of tumor antigen-specific mAbs. In addition, IFN-γ was produced by APC-like NK cells in response to tumor cells, and the cytokine production was further enhanced by mAbs. Taken together, IL-18 not only promoted the expansion of NK cells, but also changed the phenotype of NK cells. IL-2/IL-18-induced NK cells might, therefore, serve as a bridge between innate immunity and adaptive immunity and be useful for cancer immunotherapy.

A pilot study on the characteristics of circulating T follicular helper cells in liver transplant recipients

Circulating CD4⁺CXCR5⁺ T follicular helper cells (cTfh) have been demonstrated to be involved in B cell-mediated systemic autoimmune diseases and alloreactive responses following kidney transplantation; however, whether cTfh cells are involved in alloreactive responses after liver transplantation (LT) remains unclear. Our present study aimed to investigate the characteristics of cTfh, as well as CXCR3⁺CCR6^-Tfh1, CXCR3^-CCR6^-Tfh2, and CXCR3^-CCR6⁺Tfh17 subsets in liver allograft recipients. A total of 30 liver transplant recipients were enrolled in this study. The frequencies of cTfh, Tfh1, Tfh2, and Tfh17 subsets, and interleukin (IL)-21-producing Tfh cells in the circulating blood were analyzed by flow cytometry. The capacity of cTfh cells to help B cells differentiate into plasmablasts was determined one day before and one month after LT. The results revealed that the frequency of cTfh cells remained unaltered before and after LT. However, the frequency of the cTfh subsets (e.g., Tfh1 and Tfh2 cells) and B cells were reduced one month after LT. Functionally, the capacity of Tfh cells to produce IL-21 was reduced one month after LT. In addition, cTfh cells exhibited the capacity to help B cells differentiate into plasmablasts in an IL-21-dependent manner in vitro, which was reduced after LT, despite the unaltered production of IgM and IgG by plasmablasts. Thus, our data suggest that cTfh cells may be involved in alloreactive responses following LT via helping B cells differentiate into plasmablasts and plasma cells.

HLA-DR+ NK cells are mostly characterized by less mature phenotype and high functional activity

NK cells change their phenotype and functional characteristics during activation. In this work, we searched for a relationship of HLA-DR expression with differentiation stages and functional activity of NK cells ex vivo and stimulated in vitro with IL-2 challenged with gene modified feeder K562 cells expressing membrane-bound IL-21 (K562-mbIL21). This stimulation technique has been described for NK cell expansion in clinical use. We have observed that HLA-DR expression in freshly isolated circulating NK cells was mostly associated with less differentiated CD56bright CD57- cells, although in some individuals it could also be found in terminally differentiated CD57+ cells. Ex vivo HLA-DR+ NK cells possessed better capacity to produce IFN-γ in response to cytokine stimulation compared to their HLA-DR- counterparts. In vitro activation with IL-2 and K562-mbIL21 induces an increase in HLA-DR-positive NK cell proportion, again mostly among CD56bright CD57- NK cells. This happened in particular due to appearance of HLA-DR+ expression de novo in HLA-DR-negative cells. Acquired in vitro HLA-DR expression was associated with NK cell proliferation activity, more intense cytokine-induced IFN-γ production, increased degranulation toward feeder cells, and higher expression of CD86 and NKG2D. Thus, stimulation with IL-2/K562-mbIL21 causes a significant phenotype and functional shift during NK cell activation and expansion.

Review of the Clinical Pharmacokinetics and Pharmacodynamics of Alemtuzumab and Its Use in Kidney Transplantation

Alemtuzumab is a humanized monoclonal antibody against CD52 and causes depletion of T and B lymphocytes, monocytes, and NK cells. Alemtuzumab is registered for the treatment of multiple sclerosis (MS) and is also used in chronic lymphocytic leukemia (CLL). Alemtuzumab is used off-label in kidney transplantation as induction and anti-rejection therapy. The objective of this review is to present a review of the pharmacokinetics, pharmacodynamics, and use of alemtuzumab in kidney transplantation. A systematic literature search was conducted using Ovid Medline, Embase, and Cochrane Central Register of controlled trials. No pharmacokinetic or dose-finding studies of alemtuzumab have been performed in kidney transplantation. Although such studies were conducted in patients with CLL and MS, these findings cannot be directly extrapolated to transplant recipients, because CLL patients have a much higher load of CD52-positive cells and, therefore, target-mediated clearance will differ between these two indications. Alemtuzumab used as induction therapy in kidney transplantation results in a lower incidence of acute rejection compared to basiliximab therapy and comparable results as compared with rabbit anti-thymocyte globulin (rATG). Alemtuzumab used as anti-rejection therapy results in a comparable graft survival rate compared with rATG, although infusion-related side effects appear to be less. There is a need for pharmacokinetic and dose-finding studies of alemtuzumab in kidney transplant recipients to establish the optimal balance between efficacy and toxicity. Furthermore, randomized controlled trials with sufficient follow-up are necessary to provide further evidence for the treatment of severe kidney transplant rejection.

Interleukin-21 receptor signalling is not critically required for imiquimod-induced psoriasiform dermatitis in mice

Psoriasis is largely mediated by interleukin (IL)-23/T helper (Th) 17 axis, and IL-21 is a pleiotropic cytokine expressed by Th17 cells. Despite previously reported possible pathogenic roles of IL-21 in human psoriasis, we found that IL-21 receptor (IL-21R) signalling was not crucial for imiquimod-induced psoriatic inflammation, using IL-21R^-/- mice. The severity of imiquimod-induced psoriatic manifestation and pro-inflammatory Th17 cytokine levels, IL-17A-producing γδ T cells and CD4+ T cells, and in vitro IL-17A production by γδ T cells after IL-23 stimulation was comparable between wild-type and IL-21R^-/- mice. Collectively, IL-21R signalling was not critically involved in IMQ-induced psoriatic inflammation despite an increased IL-21 expression in the IMQ-treated mouse skin. Our data may represent the significant differences between human psoriasis and murine psoriasis model, and further studies using other models will be required to elucidate the role of IL-21 in psoriasis pathogenesis.

Interactions Between the Neuroendocrine System and T Lymphocytes in Diabetes

It is well established that there is a fine-tuned bidirectional communication between the immune and neuroendocrine tissues in maintaining homeostasis. Several types of immune cells, hormones, and neurotransmitters of different chemical nature are involved as communicators between organs. Apart of being key players of the adaptive arm of the immune system, it has been recently described that T lymphocytes are involved in the modulation of metabolism of several tissues in health and disease. Diabetes may result mainly from lack of insulin production (type 1 diabetes) or insufficient insulin and insulin resistance (type 2 diabetes), both influenced by genetic and environmental components. Herein, we discuss accumulating data regarding the role of the adaptive arm of the immune system in the pathogenesis of diabetes; including the action of several hormones and neurotransmitters influencing on central and peripheral T lymphocytes development and maturation, particularly under the metabolic burden triggered by diabetes. In addition, we comment on the role of T-effector lymphocytes in adipose and liver tissues during diabetes, which together enhances pancreatic β-cell stress aggravating the disease.

The self-curing phenomenon of schistosome infection in rhesus macaques: insight from in vitro studies

A reduction in the burden of schistosomiasis is potentially achievable by integrating a schistosomiasis vaccine with current control measures. Here, we determine parasite-specific in vitro responses of B, T, and NK cells from naive uninfected rhesus macaques to Schistosoma mansoni (Sm) egg (SmEA) and worm antigen (SmWA) preparations isolated from infected baboons. Pronounced B cell responses to SmEA and NK cell responses to both SmEA and SmWA were observed. High levels of IL-2 and IL-21 responses against Sm antigens were observed in T and non-T cells of lymph nodes (LNs) and gut lamina propria-derived lymphocytes (LPLs). Data analysis showed multifunctionality of LN-derived CD4⁺ , CD8⁺ , and CD4⁺ CD8⁺ double positive T cells against either SmWA or SmWA+SmEA antigen preparations. Distinct SmEA-specific multifunctional responses were observed in gut LPLs, suggesting simultaneous responses against egg antigens. These data provide insight into the immune effectors involved in schistosome responses by rhesus macaques.

Increased expression of Th17 cytokines and interleukin-22 correlates with disease activity in pristane-induced arthritis in rats

The objective of this study was to identify the key changed subtype of T helper cells (Th cells) and their cytokines in pristane-induced arthritis (PIA) in rats. The severity of arthritis was evaluated by body weight, clinical score, the perimeter of ankle and mid-paw and histological assessment of ankle joints. Cytokines of Th1, Th2 and Th17 were determined in the spleen and inguinal lymph nodes at 28 days after pristane injection by real-time qPCR. The mRNA levels of IL-22 receptors, IL-22R1 and IL-22BP, in the spleen were quantified by real-time qPCR. Additionally, IL-22 expression in synovial membrane was detected by Western blotting, and serum IL-22 concentration was determined by ELISA. Correlation between IL-22 concentration and clinical score was analyzed. By screening the cytokines of Th1, Th2 and Th17 expression profile, we found that the mRNA levels of Th17 cytokines were significantly increased in PIA rats. Particularly, a significant increase in the protein expression of IL-22 was determined in synovial membrane and serum from PIA rats, and correlated with clinical score. We conclude that IL-22 expression level was increased and correlated with disease severity, which indicated that IL-22 may play an important role in development of PIA, and was helpful to explorer the pathogenesis of rheumatoid arthritis.

IL-21 Therapy Controls Immune Activation and Maintains Antiviral CD8+ T Cell Responses in Acute Simian Immunodeficiency Virus Infection

Human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) replicate during acute infection in lymphocytes of the gastrointestinal tract, before disseminating systemically. Localized replication and associated loss of gut-resident CD4⁺ T cells occur regardless of the portal of entry of the virus (e.g., intravenous vs. rectal). Thus, HIV and SIV are tropic for gut tissue, and their pathogenesis requires the special environment of the intestine. T helper 17 (Th17) cells are important contributors to microbial defense in the gut that are vulnerable to HIV infection and whose loss is associated with translocation of microbial products to the systemic circulation, leading to chronic immune activation and disease progression. Interleukin (IL)-21 promotes differentiation and survival of Th17 cells and stimulates CD8⁺ T cell function. By promoting Th17 cell survival, IL-21 could limit bacterial translocation and immune activation in the setting of acute or rebounding HIV/SIV disease. In this study, we tested the effect of recombinant IL-21-IgFc treatment, given at the time of infection, on SIV_mac251 infection. We found that rIL-21-IgFc decreases immune activation and maintains effective antiviral responses by CD8⁺ T cells in blood, but this maintenance is not associated with lower viral loads. rIL-21-IgFc treatment also did not generally support Th17 cell populations, but Th17 cells remained strongly and independently associated with control of plasma viremia. For example, the single animal exhibiting greatest control over viremia in our study also manifested the highest levels of IL-21 in plasma, Th17 cell maintenance in blood, and Th17 cells in intestinal tissue. These findings provide rationale for further exploration of IL-21 treatment as a support for host CD8⁺ T cell responses in HIV cure strategies.

IL-21 promotes the development of a CD73-positive Vγ9Vδ2 T cell regulatory population

Vγ9Vδ2 T cells contribute to the immune response against many tumor types through their direct cytotoxic activity and capacity to regulate the biological functions of other immune cells, such as dendritic cells and IFN-γ-producing CD8⁺ T cells. However, their presence in the tumor microenvironment has also been associated with poor prognosis in breast, colon and pancreatic cancers. Additionally, recent studies demonstrated that cytokines can confer some plasticity to Vγ9Vδ2 T cells and promote their differentiation into cells with regulatory functions. Here, we demonstrated that activation of Vγ9Vδ2 T cells isolated from healthy donors and cultured in the presence of IL-21 favors the emergence of a subpopulation of Vγ9Vδ2 T cells that express the ectonucleotidase CD73 and inhibits T cell proliferation in a CD73/adenosine-dependent manner. This subpopulation produces IL-10 and IL-8 and displays lower effector functions and cytotoxic activity than CD73-negative Vγ9Vδ2 T cells. We also showed, in a syngeneic mouse tumor model, the existence of a tumor-infiltrating γδ T cell subpopulation that produces IL-10 and strongly expresses CD73. Moreover, maturation, IL-12 production and induction of antigen-specific T cell proliferation are impaired in DC co-cultured with IL-21-amplified Vγ9Vδ2 T cells. Altogether, these data indicate that IL-21 promotes Vγ9Vδ2 T cell regulatory functions by favoring the development of an immunosuppressive CD73⁺ subpopulation. Thus, when present in the tumor microenvironment, IL-21 might negatively impact γδ T cell anti-tumor functions.