IL-27 induction of IL-21 from human CD8+ T cells induces granzyme B in an autocrine manner

Revisiting the role of IL-27 in obesity-related metabolic diseases: safeguard or perturbation?

The prevalence of metabolic diseases, such as obesity, has been steadily increasing in recent years, posing a significant threat to public health. Therefore, early identification and intervention play a crucial role. With the deepening understanding of the etiology of metabolic diseases, novel therapeutic targets are emerging for the treatment of obesity, lipid metabolism disorders, cardiovascular and cerebrovascular diseases, glucose metabolism disorders, and other related metabolic conditions. IL-27, as a multi-potent cytokine, holds great promise as a potential candidate target in this regard. This article provides a comprehensive review of the latest findings on IL-27 expression and signal transduction in the regulation of immune inflammatory cells, as well as its implications in obesity and other related metabolic diseases. Furthermore, it explores the potential of IL-27 as a novel therapeutic target for the treatment of obesity and metabolic disorders. Finally, an overview is presented on both the opportunities and challenges associated with targeting IL-27 for therapeutic interventions.

An updated advancement of bifunctional IL-27 in inflammatory autoimmune diseases

Interleukin-27 (IL-27) is a member of the IL-12 family. The gene encoding IL-27 is located at chromosome 16p11. IL-27 is considered as a heterodimeric cytokine, which consists of Epstein-Barr virus (EBV)-induced gene 3 (Ebi3) and IL-27p28. Based on the function of IL-27, it binds to receptor IL-27rα or gp130 and then regulates downstream cascade. To date, findings show that the expression of IL-27 is abnormal in different inflammatory autoimmune diseases (including systemic lupus erythematosus, rheumatoid arthritis, Sjogren syndrome, Behcet's disease, inflammatory bowel disease, multiple sclerosis, systemic sclerosis, type 1 diabetes, Vogt-Koyanagi-Harada, and ankylosing spondylitis). Moreover, in vivo and in vitro studies demonstrated that IL-27 is significantly in3volved in the development of these diseases by regulating innate and adaptive immune responses, playing either an anti-inflammatory or a pro-inflammatory role. In this review, we comprehensively summarized information about IL-27 and autoimmunity based on available evidence. It is hoped that targeting IL-27 will hold great promise in the treatment of inflammatory autoimmune disorders in the future.

Surface protein and functional analyses identify CD4+CD39+ TCR αβ+ and activated TCR Vδ1+ cells with distinct pro-inflammatory functions in Crohn's disease lesions

Crohn's disease (CD) is a chronic immune-mediated disorder of the gastrointestinal tract. Extensive screening studies have revealed the accumulation of immune cell subsets with unique plasticity and immunoregulatory properties in patients with CD. We performed phenotypic and functional studies on inflamed and non-inflamed bioptic tissue to investigate the presence of distinct T cells in the intestinal mucosa of CD patients. We analysed hundreds of surface molecules expressed on cells isolated from the intestinal tissue of CD patients using anti-CD45 mAbs-based barcoding. A gene ontology enrichment analysis showed that proteins that regulate the activation of T cells were the most enriched group. We, therefore, designed T-cell focused multicolour flow-cytometry panels and performed clustering analysis which revealed an accumulation of activated TEM CD4+CD39+ T cells producing IL-17 and IL-21 and increased frequency of terminally differentiated TCR Vδ1+ cells producing TNF-α and IFN-γ in inflamed tissue of CD patients. The different functional capacities of CD4+ and TCR Vδ1+ cells in CD lesions indicate their non-overlapping contribution to inflammation. The abnormally high number of terminally differentiated TCR Vδ1+ cells suggests that they are continuously activated in inflamed tissue, making them a potential target for novel therapies.

IL-27 shapes the immune properties of human astrocytes and their impact on encountered human T lymphocytes

Background

Interleukin-27 (IL-27) can trigger both pro- and anti-inflammatory responses. This cytokine is elevated in the central nervous system (CNS) of multiple sclerosis (MS) patients, but how it influences neuroinflammatory processes remains unclear. As astrocytes express the receptor for IL-27, we sought to determine how these glial cells respond to this cytokine and whether such exposure alters their interactions with infiltrating activated T lymphocytes. To determine whether inflammation shapes the impact of IL-27, we compared the effects of this cytokine in non-inflamed and inflamed conditions induced by an IL-1β exposure.

Main body

Transcriptomic analysis of IL-27-exposed human astrocytes showed an upregulation of multiple immune genes. Human astrocytes increased the secretion of chemokines (CXCL9, CXCL10, and CXCL11) and the surface expression of proteins (PD-L1, HLA-E, and ICAM-1) following IL-27 exposure. To assess whether exposure of astrocytes to IL-27 influences the profile of activated T lymphocytes infiltrating the CNS, we used an astrocyte/T lymphocyte co-culture model. Activated human CD4⁺ or CD8⁺ T lymphocytes were co-cultured with astrocytes that have been either untreated or pre-exposed to IL‑27 or IL-1β. After 24 h, we analyzed T lymphocytes by flow cytometry for transcription factors and immune molecules. The contact with IL-27-exposed astrocytes increased the percentages of T-bet, Eomes, CD95, IL-18Rα, ICAM-1, and PD-L1 expressing CD4⁺ and CD8⁺ T lymphocytes and reduced the proportion of CXCR3-positive CD8⁺ T lymphocytes. Human CD8⁺ T lymphocytes co-cultured with human IL-27-treated astrocytes exhibited higher motility than when in contact with untreated astrocytes. These results suggested a preponderance of kinapse-like over synapse-like interactions between CD8⁺ T lymphocytes and IL-27-treated astrocytes. Finally, CD8⁺ T lymphocytes from MS patients showed higher motility in contact with IL-27-exposed astrocytes compared to healthy donors’ cells.

Conclusion

Our results establish that IL-27 alters the immune functions of human astrocytes and shapes the profile and motility of encountered T lymphocytes, especially CD8⁺ T lymphocytes from MS patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02572-1.

Skin Injury Activates a Rapid TRPV1-Dependent Antiviral Protein Response

The skin serves as the interface between the body and the environment and plays a fundamental role in innate antimicrobial host immunity. Antiviral proteins (AVPs) are part of the innate host defense system and provide protection against viral pathogens. How breach of the skin barrier influences innate AVP production remains largely unknown. In this study, we characterized the induction and regulation of AVPs after skin injury and identified a key role of TRPV1 in this process. Transcriptional and phenotypic profiling of cutaneous wounds revealed that skin injury induces high levels of AVPs in both mice and humans. Remarkably, pharmacologic and genetic ablation of TRPV1-mediated nociception abrogated the induction of AVPs, including Oas2, Oasl2, and Isg15 after skin injury in mice. Conversely, stimulation of TRPV1 nociceptors was sufficient to induce AVP production involving the CD301b+ cells‒IL-27‒mediated signaling pathway. Using IL-27 receptor‒knockout mice, we show that IL-27 signaling is required in the induction of AVPs after skin injury. Finally, loss of TRPV1 signaling leads to increased viral infectivity of herpes simplex virus. Together, our data indicate that TRPV1 signaling ensures skin antiviral competence on wounding.

Interleukin-21 in Viral Infections

Interleukin (IL)-21 is a cytokine that affects the differentiation and function of lymphoid and myeloid cells and regulates both innate and adaptive immune responses. In addition to regulating the immune response to tumor and viral infections, IL-21 also has a profound effect on the development of autoimmune and inflammatory diseases. IL-21 is produced mainly from CD4⁺ T cells-in particular, follicular helper T (Tfh) cells-which have a great influence on the regulation of antibody production. It is also an important cytokine for the activation of CD8⁺ T cells, and its role in recovering the function of CD8⁺ T cells exhausted by chronic microbial infections and cancer has been clarified. Thus, IL-21 plays an extremely important role in viral infections, especially chronic viral infections. In this review, I will introduce the findings to date on how IL-21 is involved in some typical viral infections and the potential of treating viral diseases with IL-21.

The IL-27/IL-27R axis is altered in CD4+ and CD8+ T lymphocytes from multiple sclerosis patients

Objectives

Pro‐ and anti‐inflammatory properties have been attributed to interleukin‐27 (IL‐27). Nevertheless, the impact of this cytokine on chronic inflammatory diseases such as multiple sclerosis (MS) remains ill‐defined. We investigated the biology of IL‐27 and its specific receptor IL‐27Rα in MS patients.

Methods

Levels of IL‐27 and its natural antagonist (IL‐27‐Rα) were measured by ELISA in biological fluids. CD4⁺ and CD8⁺ T lymphocytes were isolated from untreated relapsing–remitting MS patients and healthy donors. Transcriptome‐wide analysis compared T‐cell subsets stimulated or not with IL‐27. Expression of the IL‐27Rα, key immune factors, STAT phosphorylation and cytokine production was assessed by flow cytometry.

Results

We observed elevated levels of IL‐27 in the serum and cerebrospinal fluid of MS patients compared with controls. Moreover, we show that specific IL‐27‐mediated effects on T lymphocytes are reduced in MS patients including the induction of PD‐L1. IL‐27‐triggered STAT3 signalling pathway is enhanced in CD4⁺ and CD8⁺ T lymphocytes from MS patients. Elevated IL‐27Rα levels in serum from MS patients are sufficient to impair the capacity of IL‐27 to act on immune cells. We demonstrate that shedding of IL‐27Rα by activated CD4⁺ T lymphocytes from MS patients contributes to the increased IL‐27Rα peripheral levels and consequently can dampen the IL‐27 responsiveness.

Conclusion

Our work identifies several mechanisms that are altered in the IL‐27/IL‐27R axis in MS patients, especially in T lymphocytes. Our results underline the importance of characterising the biology of cytokines in human patients prior to design new therapeutics.

IL-27, a pleiotropic cytokine for fine-tuning the immune response in cancer

Interleukin (IL)-27, a member of the IL-6/IL-12 family, has an important role in modulating inflammation in partnership with innate and adaptive immune cells. IL-27 binding to IL-27R starts downstream signaling based on the target cells. It can instigate inflammation by inducing CD4⁺ T cell proliferation, Th1 polarization, cytotoxic T cell activation, generation of the natural killer cell, and macrophage and dendritic cell activation. However, by inducing programmed cell death and suppression of effector cells, IL-27 can suppress inflammation and return the immune response to hemostasis. Altogether, IL-27 displays multifaceted dual functions, which may result in either pro- or anti-inflammatory effects. Recent investigations indicated the antitumor activity of IL-27 via inducing Th1, and CTL responses and generating NK cells. On the other hand, IL-27 also can promote tumor cells' proliferation, survival, and angiogenesis. In the present review, we'll discuss recent advances concerning the role of IL-27 in inflammatory diseases such as infections, autoimmune diseases with a focus on cancer.

Interleukin-27 Functional Duality Balances Leishmania Infectivity and Pathogenesis

IL-27 is a cytokine that exerts diverse effects on the cells of innate and adaptive immune systems. Chiefly expressed in macrophages and dendritic cells during the early phase of Leishmania infection, IL-27 contributes to the protection against L. major infection but suppresses the protective Th1 response against L. donovani, L. infantum, L. amazonensis and L. braziliensis infections, suggesting its functional duality. During the late stage of Leishmania infection, IL-27 limits the immunopathogenic reactions and tissue damages. Herein, we analyze the mechanism of the functional duality of IL-27 in the resistance or susceptibility to Leishmania infection, prompting IL-27 for anti-Leishmanial therapy.

IL-27 signaling activates skin cells to induce innate antiviral proteins and protects against Zika virus infection

In the skin, antiviral proteins and other immune molecules serve as the first line of innate antiviral defense. Here, we identify and characterize the induction of cutaneous innate antiviral proteins in response to IL-27 and its functional role during cutaneous defense against Zika virus infection. Transcriptional and phenotypic profiling of epidermal keratinocytes treated with IL-27 demonstrated activation of antiviral proteins OAS1, OAS2, OASL, and MX1 in the skin of both mice and humans. IL-27-mediated antiviral protein induction was found to occur in a STAT1- and IRF3-dependent but STAT2-independent manner. Moreover, using IL27ra mice, we demonstrate a significant role for IL-27 in inhibiting Zika virus morbidity and mortality following cutaneous, but not intravenous, inoculation. Together, our results demonstrate a critical and previously unrecognized role for IL-27 in cutaneous innate antiviral immunity against Zika virus.

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.

Interleukin 21 (IL-21)/microRNA-29 (miR-29) axis is associated with natural resistance to HIV-1 infection

BACKGROUND

Interleukin-21 (IL-21) modulates HIV-1 infection through the elicitation of different antiviral mechanisms, including Th17 lineage commitment and induction of microRNA (miR)-29, a miRNA endowed with anti-HIV activity. As miR-29 expression is significantly increased in HIV-1-exposed seronegative individuals (HESN), we investigated the role of miR-29/IL21 axis in the natural control of HIV-1 infection.

METHODS

Peripheral blood mononuclear cells (PBMCs) isolated from 15 Italian sexually exposed HESN and 15 HIV-unexposed healthy controls were in-vitro infected with an R5-tropic HIV-1Ba-L strain. Seven days post HIV-1 infection we evaluated: 1) p24 production (ELISA); 2) CD4/IL-21 and CD4/IL-17 T lymphocytes (FACS); 3) IL-17 concentration in supernatants (ELISA); and 4) IL-6, IL-17, IL-21, and miR-29a,b,c expression by CD4 T lymphocytes as well as perforin and granzyme by peripheral blood mononuclear cells (qPCR). The same analyses were performed on the 15 HIV-positive partners.

RESULTS

At baseline IL-6 expression alone was increased in HESN compared to healthy controls. Seven days after in-vitro HIV-1 infection, nevertheless, differences emerged. Thus, CD4/IL21 and CD4/IL17 T lymphocytes, as well as IL-21 and IL-17 expression and production were significantly augmented in HESN compared to healthy controls. Interestingly, IL-21 upregulation correlated with a significantly increased expression of miR-29a,b,c and a reduced susceptibility to in-vitro HIV-1 infection in HESN alone. No differences were observed in perforin and granzyme expression.

CONCLUSION

The IL-21/miR-29 axis is upregulated by HIV-1 infection in HESN suggesting its involvement in the natural resistance to HIV-1 infection in HESN. Approaches that exogenously increase IL-21 production or prompt preexisting cellular IL-21 reservoir could confine the magnitude of the initial HIV-1 infection.

Tristetraprolin inhibits macrophage IL-27-induced activation of antitumour cytotoxic T cell responses

IFN-γ-producing cytotoxic T lymphocytes are essential for host defense against viral infection and cancer. Here we show that the RNA-binding tristetraprolin, encoded by Zfp36, is needed for CD8⁺ T-cell production of IFN-γ in vivo. When activated in vitro, however, IFN-γ production by naive wild type and tristetraprolin-deficient CD8⁺ T-cells is comparable. IL-27 is overproduced by tristetraprolin-deficient macrophages and increased systemically in tristetraprolin-deficient mice. Tristetraprolin suppresses IL-27 production by promoting p28 mRNA degradation. Importantly, deletion of IL-27 receptor WSX-1 in tristetraprolin-deficient mice (WSX-1/tristetraprolin double knockout) leads to a reduction in cytotoxic T lymphocyte numbers. Moreover, tumor growth is accelerated, not only in tristetraprolin-deficient mice after cytotoxic T lymphocyte depletion, but also in WSX-1/tristetraprolin double knockout mice, with substantial reduction in the number of tumor cytotoxic T lymphocytes. This study describes a regulatory pathway for IL-27 expression and cytotoxic T lymphocyte function mediated by tristetraprolin, contributing to regulation of antitumour immunity.

IL-27 is one of a number of cytokines that can induce antitumour CD8⁺ T cell responses. Here the authors show that TTP, encoded by Zfp36, degrades p28 to inhibit IL-27 production by macrophages and is thereby a negative regulator of the antitumour response.

Production of IL-27 in multiple sclerosis lesions by astrocytes and myeloid cells: Modulation of local immune responses

The mechanisms whereby human glial cells modulate local immune responses are not fully understood. Interleukin-27 (IL-27), a pleiotropic cytokine, has been shown to dampen the severity of experimental autoimmune encephalomyelitis, but it is still unresolved whether IL-27 plays a role in the human disease multiple sclerosis (MS). IL-27 contribution to local modulation of immune responses in the brain of MS patients was investigated. The expression of IL-27 subunits (EBI3 and p28) and its cognate receptor IL-27R (the gp130 and TCCR chains) was elevated within post-mortem MS brain lesions compared with normal control brains. Moreover, astrocytes (GFAP(+) cells) as well as microglia and macrophages (Iba1(+) cells) were important sources of IL-27. Brain-infiltrating CD4 and CD8 T lymphocytes expressed the IL-27R specific chain (TCCR) implying that these cells could respond to local IL-27 sources. In primary cultures of human astrocytes inflammatory cytokines increased IL-27 production, whereas myeloid cell inflammatory M1 polarization and inflammatory cytokines enhanced IL-27 expression in microglia and macrophages. Astrocytes in postmortem tissues and in vitro expressed IL-27R. Moreover, IL-27 triggered the phosphorylation of the transcription regulator STAT1, but not STAT3 in human astrocytes; indeed IL-27 up-regulated MHC class I expression on astrocytes in a STAT1-dependent manner. These findings demonstrated that IL-27 and its receptor were elevated in MS lesions and that local IL-27 can modulate immune properties of astrocytes and infiltrating immune cells. Thus, therapeutic strategies targeting IL-27 may influence not only peripheral but also local inflammatory responses within the brain of MS patients.

The Yin and Yang aspects of IL-27 in induction of cancer-specific T-cell responses and immunotherapy

Accumulating evidences from animal studies have indicated that both endogenous and exogenous IL-27, an IL-12 family of cytokine, can increase antitumor T-cell activities and inhibit tumor growth. IL-27 can modulate Treg responses, and program effector T cells into a unique T-effector stem cell (TSEC) phenotype, which enhances T-cell survival in the tumor microenvironment. However, animal studies also suggest that IL-27 induces molecular pathways such as IL-10, PD-L1 and CD39, which may downregulate tumor-specific T-cell responses. In this review paper, we will discuss the Yin and Yang aspects of IL-27 in the induction of tumor-specific T-cell responses, and the potential impacts of these functions of IL-27 in the design of cancer immunotherapy.

Biology of IL-27 and its role in the host immunity against Mycobacterium tuberculosis

IL-27, a heterodimeric cytokine of IL-12 family, regulates both innate and adaptive immunity largely via Jak-Stat signaling. IL-27 can induce IFN-γ and inflammatory mediators from T lymphocytes and innate immune cells. IL-27 has unique anti-inflammatory properties via both Tr1 cells dependent and independent mechanisms. Here the role and biology of IL-27 in innate and adaptive immunity are summarized, with special interest with immunity against Mycobacterium tuberculosis.

Committed Tc17 cells are phenotypically and functionally resistant to the effects of IL-27

IL-17-secreting CD8(+) T cells (Tc17 cells) have been implicated in immunity to infections, cancer, and autoimmune diseases. Thus far, studies on Tc17 cells have primarily investigated their development from naïve precursors, while the biology of committed Tc17 cells has been less characterized, in particular during the effector phase of immune responses. IL-27 is an important regulator of inflammation through the induction of regulatory Tr1 cells, as well as a suppressor of Th17-cell development. IL-27 suppresses the development of Tc17 cells, but its effects on committed Tc17 cells are unknown. Here we demonstrate that even though IL-27 completely inhibited the development of C57BL/6 mouse Tc17 cells, it had little effect on previously committed Tc17 cells. Although committed Tc17 cells were capable of responding to IL-27, it had no effect on expression of RORγt and RORα, or production of various cytokines. Committed Tc17 cells did not express granzyme B and lacked cytotoxicity in vitro, features that remained unaltered by IL-27 treatment. Nonetheless, they efficiently induced diabetes, irrespective of treatment with IL-27 prior to transfer into RIP-mOVA mice. These findings suggest that use of IL-27 to modulate autoimmune diseases might have limited therapeutic efficacy if autoaggressive Tc17 cells have already developed.

Human IL-21 and IL-21R deficiencies: two novel entities of primary immunodeficiency

PURPOSE OF REVIEW

This review highlights the recent identification of human interleukin-21 (IL-21) and interleukin-21 receptor (IL-21R) deficiencies as novel entities of primary immunodeficiency.

RECENT FINDINGS

We recently described the first patients with IL-21R deficiency who had cryptosporidial infections associated with chronic cholangitis and liver disease. All IL-21R-deficient patients suffered from recurrent respiratory tract infections. Immunological work-up revealed impaired B cell proliferation and immunoglobulin class-switch, reduced T cell effector functions, and variable natural killer cell dysfunctions. Recently, these findings have been extended by the discovery of one patient with a mutation in the IL21 gene. This patient predominantly manifested with very early onset inflammatory bowel disease and recurrent respiratory infections. Laboratory examination showed reduced circulating B cells and impaired B cell class-switch.

SUMMARY

Human IL-21 and IL-21R deficiencies cause severe, primary immunodeficiency reminiscent of common variable immunodeficiency. Early diagnosis is critical to prevent life-threatening complications, such as secondary liver failure. In view of the critical role of IL-21 in controlling immune homeostasis, early hematopoietic stem cell transplantation might be considered as therapeutic intervention in affected children.

Interleukin-21 and T follicular helper cells in HIV infection: research focus and future perspectives

Interleukin (IL)-21 is a member of the γ chain-receptor cytokine family along with IL-2, IL-4, IL-7, IL-9, and IL-15. The effects of IL-21 are pleiotropic, owing to the broad cellular distribution of the IL-21 receptor. IL-21 is secreted by activated CD4 T cells and natural killer T cells. Within CD4 T cells, its secretion is restricted mainly to T follicular helper (Tfh) cells and Th17 cells to a lesser extent. Our research focus has been on the role of IL-21 and more recently of Tfh in immunopathogenesis of HIV infection. This review focuses on first the influence of IL-21 in regulation of T cell, B cell, and NK cell responses and its immunotherapeutic potential in viral infections and as a vaccine adjuvant. Second, we discuss the pivotal role of Tfh in generation of antibody responses in HIV-infected persons in studies using influenza vaccines as a probe. Lastly, we review data supporting ability of HIV to infect Tfh and the role of these cells as reservoirs for HIV and their contribution to viral persistence.

Immune activation is associated with CD8 T cell interleukin-21 production in HIV-1-infected individuals

Interleukin-21 (IL-21) can be produced by CD8 T cells from HIV-1-infected individuals and those with autoimmune disease, but the mechanism remains poorly understood. Here we demonstrate that IL-21-producing CD8 T cells are not associated with CD4 depletion and are absent in patients with idiopathic CD4 lymphocytopenia. Instead, IL-21 production by CD8 T cells was associated with high levels of activation, suggesting that these cells emerge as a consequence of excessive chronic immune activation rather than CD4 lymphopenia.

Interleukin-21: a double-edged sword with therapeutic potential

Interleukin-21 is a cytokine with broad pleiotropic actions that affect the differentiation and function of lymphoid and myeloid cells. Since its discovery in 2000, a tremendous amount has been learned about its biological actions and the molecular mechanisms controlling IL-21-mediated cellular responses. IL-21 regulates both innate and adaptive immune responses, and it not only has key roles in antitumour and antiviral responses but also exerts major effects on inflammatory responses that promote the development of autoimmune diseases and inflammatory disorders. Numerous studies have shown that enhancing or inhibiting the action of IL-21 has therapeutic effects in animal models of a wide range of diseases, and various clinical trials are underway. The current challenge is to understand how to specifically modulate the actions of IL-21 in the context of each specific immune response or pathological situation. In this Review, we provide an overview of the basic biology of IL-21 and discuss how this information has been - and can be - exploited therapeutically.

The role of IL-27 in the induction of anti-tumor cytotoxic T lymphocyte response

Cytotoxic T lymphocyte (CTL) response is a critical component of the immune response to tumors, therefore optimal induction of CTL responses to tumor antigens is highly desired for developing efficient cancer immunotherapy. IL-27 is a member of the IL-12 family of cytokines that is comprised of an IL-12 p40-related protein subunit, EBV-induced gene 3 (EBI3), and a p35-related subunit, p28. IL-27 functions through IL-27R and has been shown to have potent anti-tumor activity via activation of a variety of immune components, including anti-tumor CD8(+) T cell responses. However, the exact mechanisms of how IL-27 enhances anti-tumor CD8(+) T cell responses are not fully understood. In this paper we mainly discuss the evidences that suggest novel mechanisms by which IL-27 enhances anti-tumor CTL responses, including IL-27 inhibition of activation-induced cell death; the phenotypes of IL-27-stimulated CTLs; IL-27-induced CTL IL-10/IL-21 production and IL-27-mediated suppression of regulatory T cell responses. These evidences suggest that IL-27 may have a great potential to be utilized in boosting anti-tumor CTL responses in human cancer patients.