IL-21 enhances dendritic cell ability to induce interferon-gamma production by natural killer T cells

iNKT: A new avenue for CAR-based cancer immunotherapy

Chimeric antigen receptor (CAR) T cell is a T lymphocyte-based immunotherapy, which achieves great successes in treating blood malignancies and provides new hope to cue advanced cancer patients. Invariant natural killer T (iNKT) cells are a kind of special T lymphocytes characterized by expressing invariant TCR of Vα24Vβ11 to recognize CD1d-presented glycolipid antigens, which bridge innate and adaptive immune responses. iNKT cells themselves show strong anti-tumor effect in tumor models via CD1d-mediated killing of CD1d-positive tumor cells and immunosuppressive TAMs and MDSCs, and are closely related to the prognosis of cancer patients. iNKT cells are not restricted to polymorphic human leukocyte antigen (HLA) and can prevent Graft versus Host Disease (GvHD), which makes it to be an ideal CAR vector for allogeneic therapy. Although CAR-iNKT was developed and verified by several different teams and attracts more and more attentions, many obstacles are still needed to be resolved before obtaining CAR-iNKT therapeutics. In this review, we summarized the current status of clinical application of iNKT cells and the latest achievements of CAR-iNKT cells, which provides new insight in CAR-iNKT development and usages.

Activation of iNKT Cells Facilitates Liver Repair After Hepatic Ischemia Reperfusion Injury Through Acceleration of Macrophage Polarization

Macrophage polarization is critical for liver tissue repair following acute liver injury. However, the underlying mechanisms of macrophage phenotype switching are not well defined. Invariant natural killer T (iNKT) cells orchestrate tissue inflammation and tissue repair by regulating cytokine production. Herein, we examined whether iNKT cells played an important role in liver repair after hepatic ischemia-reperfusion (I/R) injury by affecting macrophage polarization. To this end, we subjected male C57BL/6 mice to hepatic I/R injury, and mice received an intraperitoneal (ip) injection of α-galactosylceramide (α-GalCer) or vehicle. Compared with that of the vehicle, α-GalCer administration resulted in the promotion of liver repair accompanied by acceleration of macrophage differentiation and by increases in the numbers of Ly6C^high pro-inflammatory macrophages and Ly6C^low reparative macrophages. iNKT cells activated with α-GalCer produced interleukin (IL)-4 and interferon (IFN)-γ. Treatment with anti-IL-4 antibodies delayed liver repair, which was associated with an increased number of Ly6C^high macrophages and a decreased number of Ly6C^low macrophages. Treatment with anti-IFN-γ antibodies promoted liver repair, associated with reduced the number of Ly6C^high macrophages, but did not change the number of Ly6C^low macrophages. Bone marrow-derived macrophages up-regulated the expression of genes related to both a pro-inflammatory and a reparative phenotype when co-cultured with activated iNKT cells. Anti-IL-4 antibodies increased the levels of pro-inflammatory macrophage-related genes and decreased those of reparative macrophage-related genes in cultured macrophages, while anti-IFN-γ antibodies reversed the polarization of macrophages. Cd1d-deficient mice showed delayed liver repair and suppressed macrophage switching, compared with that in wild-type mice. These results suggest that the activation of iNKT cells by α-GalCer facilitated liver repair after hepatic I/R injury by both IL-4-and IFN-γ-mediated acceleration of macrophage polarization. Therefore, the activation of iNKT cells may represent a therapeutic tool for liver repair after hepatic I/R injury.

A pan-cancer single-cell transcriptional atlas of tumor infiltrating myeloid cells

Tumor-infiltrating myeloid cells (TIMs) are key regulators in tumor progression, but the similarity and distinction of their fundamental properties across different tumors remain elusive. Here, by performing a pan-cancer analysis of single myeloid cells from 210 patients across 15 human cancer types, we identified distinct features of TIMs across cancer types. Mast cells in nasopharyngeal cancer were found to be associated with better prognosis and exhibited an anti-tumor phenotype with a high ratio of TNF+/VEGFA+ cells. Systematic comparison between cDC1- and cDC2-derived LAMP3+ cDCs revealed their differences in transcription factors and external stimulus. Additionally, pro-angiogenic tumor-associated macrophages (TAMs) were characterized with diverse markers across different cancer types, and the composition of TIMs appeared to be associated with certain features of somatic mutations and gene expressions. Our results provide a systematic view of the highly heterogeneous TIMs and suggest future avenues for rational, targeted immunotherapies.

Interleukin-21 (IL-21) Downregulates Dendritic Cell Cytokine Responses to Helicobacter pylori and Modulates T Lymphocyte IL-17A Expression in Peyer's Patches during Infection

Interleukin-21 (IL-21), a cytokine produced by many subsets of activated immune cells, is critical for driving inflammation in several models. Using Helicobacter pylori infection as a model for chronic mucosal infection, we previously published that IL-21 is required for the development of gastritis in response to infection. Concomitant with protection from chronic inflammation, H. pylori-infected IL-21^-/- mice exhibited limited Th1 and Th17 responses in their gastric mucosa. Here we report that H. pylori-infected IL-21^-/- mice express significantly higher levels of IL-17A than H. pylori-infected wild-type (WT) mice in the Peyer's patches and mesenteric lymph nodes. This led us to hypothesize that IL-21 may indirectly regulate H. pylori-specific T cell responses by controlling dendritic cell (DC) functions in mucosa-associated lymphoid tissue. It was found that IL-21 treatment reduced the ability of dendritic cells to produce proinflammatory cytokines in response to H. pylori While H. pylori increased the expression of costimulatory proteins on DCs, IL-21 reduced the expression of CD40 in the presence of H. pylori Also, Th17 recall responses were intact when DCs were used as antigen-presenting cells in the presence of IL-21, but IL-21 did impact the ability of DCs to induce antigen-specific proliferation. These data suggest that IL-21, while proinflammatory in most settings, downregulates the proinflammatory cytokine microenvironment through modulating the cytokine expression of DCs, indirectly modifying IL-17A expression. Understanding how these proinflammatory cytokines are regulated will advance our understanding of how and why H. pylori infection may be tolerated in some individuals while it causes gastritis, ulcers, or cancer in others.

A pathogenetic role for IL-21 in primary Sjögren syndrome

Advances in our understanding of the pathogenesis of primary Sjögren syndrome (pSS) characterize it as a highly complex process encompassing both the initiation of innate immunity and subsequent adaptive immune responses. IL-21 is receiving attention as a potential key player in the pathogenesis of pSS owing to its pleiotropic effects on the type I interferon signalling pathway, and newly identified roles in generation of follicular and IL-17-producing subtypes of helper T cells, as well as plasma-cell differentiation and B-cell activation. Taking into consideration the diverse biological functions of IL-21 and its clinical relevance to pSS, we propose that this cytokine has a central role in orchestrating the complex immune response in pSS. This hypothesis might provide new insight into the pathogenesis of pSS and facilitate the development of effective therapeutic strategies.

IL-21 promotes CD4 T cell responses by phosphatidylinositol 3-kinase-dependent upregulation of CD86 on B cells

The cytokine IL-21 is a potent immune modulator with diverse mechanisms of action on multiple cell types. IL-21 is in clinical use to promote tumor rejection and is an emerging target for neutralization in the setting of autoimmunity. Despite its clinical potential, the biological actions of IL-21 are not yet fully understood and the full range of effects of this pleiotropic cytokine are still being uncovered. In this study, we identify a novel role for IL-21 as an inducer of the costimulatory ligand CD86 on B lymphocytes. CD86 provides critical signals through T cell-expressed CD28 that promote T cell activation in response to Ag engagement. Expression levels of CD86 are tightly regulated in vivo, being actively decreased by regulatory T cells and increased in response to pathogen-derived signals. In this study, we demonstrate that IL-21 can trigger potent and sustained CD86 upregulation through a STAT3 and PI3K-dependent mechanism. We show that elevated CD86 expression has functional consequences for the magnitude of CD4 T cell responses both in vitro and in vivo. These data pinpoint CD86 upregulation as an additional mechanism by which IL-21 can elicit immunomodulatory effects.

Activation of cellular immunity and marked inhibition of liver cancer in a mouse model following gene therapy and tumor expression of GM-SCF, IL-21, and Rae-1

Background

Cancer is both a systemic and a genetic disease. The pathogenesis of cancer might be related to dampened immunity. Host immunity recognizes nascent malignant cells – a process referred to as immune surveillance. Augmenting immune surveillance and suppressing immune escape are crucial in tumor immunotherapy.

Methods

A recombinant plasmid capable of co-expressing granulocyte-macrophage colony- stimulating factor (GM-SCF), interleukin-21 (IL-21), and retinoic acid early transcription factor-1 (Rae-1) was constructed, and its effects determined in a mouse model of subcutaneous liver cancer. Serum specimens were assayed for IL-2 and INF-γ by ELISA. Liver cancer specimens were isolated for Rae-1 expression by RT-PCR and Western blot, and splenocytes were analyzed by flow cytometry.

Results

The recombinant plasmid inhibited the growth of liver cancer and prolonged survival of tumor-loaded mice. Activation of host immunity might have contributed to this effect by promoting increased numbers and cytotoxicity of natural killer (NK) cells and cytotoxic T lymphocytes (CTL) following expression of GM-SCF, IL-21, and Rae-1. By contrast, the frequency of regulatory T cells was decreased, Consequently, activated CTL and NK cells enhanced their secretion of INF-γ, which promoted cytotoxicity of NK cells and CTL. Moreover, active CTL showed dramatic secretion of IL-2, which stimulates CTL. The recombinant expression plasmid also augmented Rae-1 expression by liver cancer cells. Rae-1 receptor expressing CTL and NK cells removed liver cancer.

Conclusions

The recombinant expression plasmid inhibited liver cancer by a mechanism that involved activation of cell-mediated immunity and Rae-1 in liver cancer.

Functional characterization of a nonmammalian IL-21: rainbow trout Oncorhynchus mykiss IL-21 upregulates the expression of the Th cell signature cytokines IFN-gamma, IL-10, and IL-22

In mammals, IL-21 is a common γ chain cytokine produced by activated CD4(+) T cells and NKT cells that acts on multiple lineages of cells. Although IL-21 has also been discovered in birds, amphibians, and fish, to date, no functional studies have been reported for any nonmammalian IL-21 molecule. We have sequenced an IL-21 gene (tIL-21) in rainbow trout, which has a six-exon/five-intron structure, is expressed in immune tissues, and is induced by bacterial and viral infection and the T cell stimulant PHA. In contrast to mammals, calcium ionophore and PMA act synergistically to induce tIL-21. Recombinant tIL-21 (rtIL-21) induced a rapid and long-lasting (4-72 h) induction of expression of IFN-γ, IL-10, and IL-22, signature cytokines for Th1-, Th2-, and Th17-type responses, respectively, in head kidney leukocytes. However, rtIL-21 had little effects on the expression of other cytokines studied. rtIL-21 maintained the expression of CD8α, CD8β, and IgM at a late stage of stimulation when their expression was significantly decreased in controls and increased the expression of the Th cell markers CD4, T-bet, and GATA3. Intraperitoneal injection of rtIL-21 confirmed the in vitro bioactivity and increased the expression of IFN-γ, IL-10, IL-21, IL-22, CD8, and IgM. Inhibition experiments revealed that the activation of JAK/STAT3, Akt1/2, and PI3K pathways were responsible for rtIL-21 action. This study helps to clarify the role of IL-21 in lower vertebrates for the first time, to our knowledge, and suggests IL-21 is a likely key regulator of T and B cell function in fish.

Raising the NKT cell family

Natural killer T cells (NKT cells) are CD1d-restricted, lipid antigen-reactive, immunoregulatory T lymphocytes that can promote cell-mediated immunity to tumors and infectious organisms, including bacteria and viruses, yet paradoxically they can also suppress the cell-mediated immunity associated with autoimmune disease and allograft rejection. Furthermore, in some diseases, such as atherosclerosis and allergy, NKT cell activity can be deleterious to the host. Although the precise means by which these cells carry out such contrasting functions is unclear, recent studies have highlighted the existence of many functionally distinct NKT cell subsets. Because their frequency and number vary widely between individuals, it is important to understand the mechanisms that regulate the development and maintenance of NKT cells and subsets thereof, which is the subject of this review.

IL-17 produced by neutrophils regulates IFN-gamma-mediated neutrophil migration in mouse kidney ischemia-reperfusion injury

The IL-23/IL-17 and IL-12/IFN-gamma cytokine pathways have a role in chronic autoimmunity, which is considered mainly a dysfunction of adaptive immunity. The extent to which they contribute to innate immunity is, however, unknown. We used a mouse model of acute kidney ischemia-reperfusion injury (IRI) to test the hypothesis that early production of IL-23 and IL-12 following IRI activates downstream IL-17 and IFN-gamma signaling pathways and promotes kidney inflammation. Deficiency in IL-23, IL-17A, or IL-17 receptor (IL-17R) and mAb neutralization of CXCR2, the p19 subunit of IL-23, or IL-17A attenuated neutrophil infiltration in acute kidney IRI in mice. We further demonstrate that IL-17A produced by GR-1+ neutrophils was critical for kidney IRI in mice. Activation of the IL-12/IFN-gamma pathway and NKT cells by administering alpha-galactosylceramide-primed bone marrow-derived DCs increased IFN-gamma production following moderate IRI in WT mice but did not exacerbate injury or enhance IFN-gamma production in either Il17a-/- or Il17r-/- mice, which suggested that IL-17 signaling was proximal to IFN-gamma signaling. This was confirmed by the finding that IFN-gamma administration reversed the protection seen in Il17a-/- mice subjected to IRI, whereas IL-17A failed to reverse protection in Ifng-/- mice. These results demonstrate that the innate immune component of kidney IRI requires dual activation of the IL-12/IFN-gamma and IL-23/IL-17 signaling pathways and that neutrophil production of IL-17A is upstream of IL-12/IFN-gamma. These mechanisms might contribute to reperfusion injury in other organs.

Endogenous IL-21 restricts CD8+ T cell expansion and is not required for tumor immunity

IL-21 has antitumor activity through actions on NK cells and CD8(+) T cells, and is currently in clinical development for the treatment of cancer. However, no studies have addressed the role of endogenous IL-21 in tumor immunity. In this study, we have studied both primary and secondary immune responses in IL-21(-/-) and IL-21R(-/-) mice against several experimental tumors. We found intact immune surveillance toward methylcholanthrene-induced sarcomas in IL-21(-/-) and IL-21R(-/-) mice compared with wild-type mice and B16 melanomas showed equal growth kinetics and development of lung metastases. IL-21R(-/-) mice showed competent NK cell-mediated rejection of NKG2D ligand (Rae1beta) expressing H-2b(-) RMAS lymphomas and sustained transition to CD8(+) T cell-dependent memory against H-2b(+) RMA lymphomas. alpha-Galactosylceramide stimulation showed equal expansion and activation of NKT and NK cells and mounted a powerful antitumor response in the absence of IL-21 signaling, despite reduced expression of granzyme B in NKT, NK, and CD8(+) T cells. Surprisingly, host IL-21 significantly restricted the expansion of Ag-specific CD8(+) T cells and inhibited primary CD8(+) T cell immunity against OVA-expressing EG7 lymphomas, as well as the secondary expansion of memory CD8(+) T cells. However, host IL-21 did not alter the growth of less immunogenic MC38 colon carcinomas with dim OVA expression. Overall, our results show that endogenous IL-21/IL-21R is not required for NK, NKT, and CD8(+) T cell-mediated tumor immunity, but restricts Ag-specific CD8(+) T cell expansion and rejection of immunogenic tumors, indicating novel immunosuppressive actions of this cytokine.

IL-21: roles in immunopathology and cancer therapy

Cytokines are secreted signalling molecules with decisive effects on haematopoiesis, innate and adaptive immunity, and immunopathology. Interleukin (IL)-21 is a novel cytokine produced by activated CD4(+) T cells and natural killer T (NKT) cells. IL-21 is part of a family of cytokines which include IL-2, -4, -7, -9 and -15 that all share the common IL-2 receptor gamma chain (gamma(c)) in their individual receptor complexes. IL-21 receptor (IL-21R) is widely expressed on both myeloid and lymphoid cell lineages and IL-21 actions include co-stimulation of B cell differentiation and immunoglobulin (Ig) production, co-mitogen of T cells, and stimulation of NK and CD8(+) T cell cytotoxic function. Initially, IL-21 was recognized for its anti-tumour effects in several preclinical tumour models, warranting its currently ongoing clinical development as a cancer immunotherapeutic. More recently, IL-21 has been associated with the development of a panel of autoimmune and inflammatory diseases, where neutralization of IL-21 has been suggested as a potential new therapy. In this review, we will cover the latest discoveries of IL-21 as a cancer therapy and its implications in immunopathologies.

A polymorphism within IL21R confers risk for systemic lupus erythematosus

OBJECTIVE

Interleukin-21 (IL-21) is a member of the type I cytokine superfamily that has a variety of effects on the immune system, including B cell activation, plasma cell differentiation, and immunoglobulin production. The expression of IL-21 receptor (IL-21R) is reduced in the B cells of patients with systemic lupus erythematosus (SLE), while serum IL-21 levels are increased both in lupus patients and in some murine lupus models. We recently reported that polymorphisms within the IL21 gene are associated with increased susceptibility to SLE. The aim of this study was to examine the genetic association between single-nucleotide polymorphisms (SNPs) within IL21R and SLE.

METHODS

We genotyped 17 SNPs in the IL21R gene in 2 large cohorts of lupus patients (a European-derived cohort and a Hispanic cohort) and in ethnically matched healthy controls.

RESULTS

We identified and confirmed the association between rs3093301 within the IL21R gene and SLE in the 2 cohorts (meta-analysis odds ratio 1.16 [95% confidence interval 1.08-1.25], P=1.0x10(-4)).

CONCLUSION

Our findings indicate that IL21R is a novel susceptibility gene for SLE.

Interleukin-10/interleukin-5 responses at birth predict risk for respiratory infections in children with atopic family history

RATIONALE

Respiratory infections in early life are associated with risk for wheezing bronchiolitis, especially in children at high risk of atopy. The underlying mechanisms are unknown, but are suspected to involve imbalance(s) in host defense responses against pathogens stemming from functional immaturity of the immune system in this age group.

OBJECTIVES

To assess the contribution of eosinophil-trophic IL-5, and the potent antiinflammatory cytokine IL-10, to risk for infection in early life.

MEASUREMENTS AND MAIN RESULTS

We prospectively monitored a cohort of 198 high-risk children to age 5 years, recording every acute respiratory infection episode and classifying them by severity. We measured cord blood T-cell capacity to produce IL-10 and IL-5, and related these functions to subsequent infection history. IL-10 and IL-5 were associated, respectively, with resistance versus susceptibility to infections. The greatest contrasting effects of these two cytokines were seen when they were considered in combination by generating IL-10/IL-5 response ratios for each subject. The low IL-10/high IL-5 T-cell response phenotype was strongly associated with susceptibility to all grades of acute respiratory infection, relative to the more resistant high IL-10/low IL-5 phenotype.

CONCLUSIONS

Excessive production of IL-5 by T cells at birth is associated with heightened risk for subsequent severe respiratory infections, and this risk is attenuated by concomitant IL-10 production. The underlying mechanisms may involve IL-10-mediated feedback inhibition of IL-5-dependent eosinophil-induced inflammation, which is a common feature of host antiviral responses in early life.

The mechanism of development of acute lung injury in lethal endotoxic shock using alpha-galactosylceramide sensitization

The mechanism underlying acute lung injury in lethal endotoxic shock induced by administration of lipopolysaccharide (LPS) into alpha-galactosylceramide (alpha-GalCer)-sensitized mice was studied. Sensitization with alpha-GalCer resulted in the increase of natural killer T (NK T) cells and the production of interferon (IFN)-gamma in the lung. The IFN-gamma that was produced induced expression of adhesion molecules, especially vascular cell adhesion molecule-1 (VCAM-1), on vascular endothelial cells in the lung. Anti-IFN-gamma antibody inhibited significantly the VCAM-1 expression in alpha-GalCer-sensitized mice. Very late activating antigen-4-positive cells, as the counterpart of VCAM-1, accumulated in the lung. Anti-VCAM-1 antibody prevented LPS-mediated lethal shock in alpha-GalCer-sensitized mice. The administration of LPS into alpha-GalCer-sensitized mice caused local production of excessive proinflammatory mediators, such as tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6 and nitric oxide. LPS caused microvascular leakage of proteins and cells into bronchoalveolar lavage fluid. Taken together, sensitization with alpha-GalCer was suggested to induce the expression of VCAM-1 via IFN-gamma produced by NK T cells and recruit a number of inflammatory cells into the lung. Further, LPS was suggested to lead to the production of excessive proinflammatory mediators, the elevation of pulmonary permeability and cell death. The putative mechanism of acute lung injury in LPS-mediated lethal shock using alpha-GalCer sensitization is discussed.

Chemical modification of iGb3 increases IFN-gamma production by hepatic NKT cells

Isoglobotrihexosylceramide (iGb3) has been identified as an endogenous ligand recognized by NKT cells; however, it is a weak agonist compared to the exogenous alpha-galactosylceramide. Modification of the structure of iGb3 might improve its stimulatory activity. In this study, we assessed the stimulating activity of chemically-modified iGb3 analogues on murine hepatic NKT cells. We analyzed the percentage of IFN-gamma- or IL-4-producing cells in hepatic iNKT cell population and found that two chemically-modified iGb3 analogues, especially 4'''-dh-iGb3, induced significantly greater intracellular IFN-gamma+ NKT cells in liver by flow cytometry. In vivo experiments also showed that 4-HO-iGb3 and 4'''-dh-iGb3 are selectively strong inducer for rapid serum IFN-gamma production compared with unmodified iGb3. Comparing the structure of iGb3 and its two iGb3 analogues, 4-HO-iGb3 has an extra hydroxy group on C4, suggesting that the additional hydroxy group of phytosphingosine might augment the stability of the CD1d/glycoceramide complex forming and thereby possibly promote IFN-gamma producing. By further modifying the polysaccharide of glycolipid as did in 4'''-dh-iGb3, we found that 4'''-dh-iGb3 elicited more Th1-biased responses than iGb3 and 4-HO-iGb3. This modification might more strongly strengthen the affinity of the TCR/glycoceramide complex and ultimately polarize iNKT cells to release more Th1 cytokines. Our data suggests that a combination modification on both polysaccharide and sphingosine chain of iGb3 elicits preferential Th1-biased responses.