Interleukin-2 rescues helpless effector CD8+ T cells by diminishing the susceptibility to TRAIL mediated death

IL-2-mediated hepatotoxicity: knowledge gap identification based on the irAOP concept

Drug-induced hepatotoxicity constitutes a major reason for non-approval and post-marketing withdrawal of pharmaceuticals. In many cases, preclinical models lack predictive capacity for hepatic damage in humans. A vital concern is the integration of immune system effects in preclinical safety assessment. The immune-related Adverse Outcome Pathway (irAOP) approach, which is applied within the Immune Safety Avatar (imSAVAR) consortium, presents a novel method to understand and predict immune-mediated adverse events elicited by pharmaceuticals and thus targets this issue. It aims to dissect the molecular mechanisms involved and identify key players in drug-induced side effects. As irAOPs are still in their infancy, there is a need for a model irAOP to validate the suitability of this tool. For this purpose, we developed a hepatotoxicity-based model irAOP for recombinant human IL-2 (aldesleukin). Besides producing durable therapeutic responses against renal cell carcinoma and metastatic melanoma, the boosted immune activation upon IL-2 treatment elicits liver damage. The availability of extensive data regarding IL-2 allows both the generation of a comprehensive putative irAOP and to validate the predictability of the irAOP with clinical data. Moreover, IL-2, as one of the first cancer immunotherapeutics on the market, is a blueprint for various biological and novel treatment regimens that are under investigation today. This review provides a guideline for further irAOP-directed research in immune-mediated hepatotoxicity.

The Role of TRAIL/DRs in the Modulation of Immune Cells and Responses

Expression of TRAIL (tumor necrosis factor–related apoptosis–inducing ligand) by immune cells can lead to the induction of apoptosis in tumor cells. However, it becomes increasingly clear that the interaction of TRAIL and its death receptors (DRs) can also directly impact immune cells and influence immune responses. Here, we review what is known about the role of TRAIL/DRs in immune cells and immune responses in general and in the tumor microenvironment in particular.

Regulation of Effector and Memory CD8 T Cell Differentiation by IL-2-A Balancing Act

Interleukin-2 (IL-2) regulates key aspects of CD8 T cell biology–signaling through distinct pathways IL-2 triggers critical metabolic and transcriptional changes that lead to a spectrum of physiological outcomes such as cell survival, proliferation, and effector differentiation. In addition to driving effector differentiation, IL-2 signals are also critical for formation of long-lived CD8 T cell memory. This review discusses a model of rheostatic control of CD8 T cell effector and memory differentiation by IL-2, wherein the timing, duration, dose, and source of IL-2 signals are considered in fine-tuning the balance of key transcriptional regulators of cell fate.

Analysis of the roles of dietary protein and calcium in fluoride-induced changes in T-lymphocyte subsets in rat

The roles of dietary protein (Pr) and calcium (Ca) levels on the changes in T-lymphocyte subsets induced by excessive fluoride (F) intake were assessed using rats that were malnourished for 120 days as a model. The CD⁴⁺ and CD⁸⁺ T-lymphocytes in the spleen tissue were determined by flow cytometry and immunofluorescence assay. The percentages of CD³⁺ , CD⁴⁺ , and CD⁸⁺ T-lymphocytes were reduced in the spleen of rats exposed to excessive F, and malnutrition aggravated these changes in the T-lymphocytes. In addition, the mRNA expression levels of IL-1β, IL-2, IL-6, TNF-α, and IFN-γ in the spleen were downregulated significantly. We also reported herein the increased apoptosis ratio following caspase-9 and caspase-3 upregulation in the spleen of rats exposed to excessive amount of F. Light and transmisison electron microscopy revealed the irregularly arranged lymphocytes, few lymph nodules and the apoptotic characteristic of lymphocytes, which are caused by the increased expression of caspase. In addition, Pr and Ca supplementation reversed the morphologic and T-lymphocytic changes in spleen under malnutrition. Taken together, our results revealed an endogenous caspase-mediated mechanism of regulating the apoptosis of the T-lymphocyte subsets, as well as the immune-related cytokine secretion, which reduces the immune function in F-induced rats. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1587-1595, 2017.

Relationship between XspI Site Polymorphisms of LDL-R Gene and Serum IL-2 and IL-10 in Patients with Hypercholesterolemia

BACKGROUND

Relationship has been identified in sporadic reports between polymorphisms and hypercholesterolemia. However, the relationship between inflammatory cytokines and polymorphism of low-density lipoprotein receptor (LDL-R) gene in hypercholesterolemia is unclear. This study aimed to explore the relationship and significance between polymorphisms of LDL-R gene and serum Interleukin-2 (IL-2), IL-10 in patients with hypercholesterolemia.

METHODS

PCR-RFLP and direct DNA sequencing assay were employed to determine polymorphism of LDL-R gene in 900 patients with hypercholesterolemia and 400 healthy cases. ELISA was applied to assay serum concentration of IL-2 and IL-10. Blood lipid indexes were tested in all cases.

RESULTS

Compared with the healthy controls, level of IL-2 increased significantly, while IL-10 decreased significantly (P < 0.05). Correlation analysis showed that IL-2 was positively correlated with total cholesterol (TC), LDL-c, and genotype (r = 0.542, 0.410, 0.598, P < 0.05) and negatively correlated with HDL-c (r = -0.352, P < 0.05). Negative relationship also was found between TC, LDL-c, genotype, and IL-10 (r = -0.452, -0.390, -0.613, P < 0.05), and positive correlation between HDL-c and IL-10 (r = 0.398, P < 0.05). Multiple linear regression showed that genotypes and TC were independent factors affecting the levels of IL-2 and IL-10 (P < 0.05).

CONCLUSION

IL-2 and IL-10 were related to gene polymorphisms of LDL-R, which might be involved in the development and progress of hypercholesterolemia.

Therapeutic applications of TRAIL receptor agonists in cancer and beyond

TRAIL/Apo-2L is a member of the TNF superfamily first described as an apoptosis-inducing cytokine in 1995. Similar to TNF and Fas ligand, TRAIL induces apoptosis in caspase-dependent manner following TRAIL death receptor trimerization. Because tumor cells were shown to be particularly sensitive to this cytokine while normal cells/tissues proved to be resistant along with being able to synthesize and release TRAIL, it was rapidly appreciated that TRAIL likely served as one of our major physiologic weapons against cancer. In line with this, a number of research laboratories and pharmaceutical companies have attempted to exploit the ability of TRAIL to kill cancer cells by developing recombinant forms of TRAIL or TRAIL receptor agonists (e.g., receptor-specific mAb) for therapeutic purposes. In this review article we will describe the biochemical pathways used by TRAIL to induce different cell death programs. We will also summarize the clinical trials related to this pathway and discuss possible novel uses of TRAIL-related therapies. In recent years, the physiological importance of TRAIL has expanded beyond being a tumoricidal molecule to one critical for a number of clinical settings - ranging from infectious disease and autoimmunity to cardiovascular anomalies. We will also highlight some of these conditions where modulation of the TRAIL/TRAIL receptor system may be targeted in the future.

TCAIM decreases T cell priming capacity of dendritic cells by inhibiting TLR-induced Ca2+ influx and IL-2 production

We previously showed that the T cell activation inhibitor, mitochondrial (Tcaim) is highly expressed in grafts of tolerance-developing transplant recipients and that the encoded protein is localized within mitochondria. In this study, we show that CD11c(+) dendritic cells (DCs), as main producers of TCAIM, downregulate Tcaim expression after LPS stimulation or in vivo alloantigen challenge. LPS-stimulated TCAIM-overexpressing bone marrow-derived DC (BMDCs) have a reduced capacity to induce proliferation of and cytokine expression by cocultured allogeneic T cells; this is not due to diminished upregulation of MHC or costimulatory molecules. Transcriptional profiling also revealed normal LPS-mediated upregulation of the majority of genes involved in TLR signaling. However, TCAIM BMDCs did not induce Il2 mRNA expression upon LPS stimulation in comparison with Control-BMDCs. In addition, TCAIM overexpression abolished LPS-mediated Ca(2+) influx and mitochondrial reactive oxygen species formation. Addition of IL-2 to BMDC-T cell cocultures restored the priming capacity of TCAIM BMDCs for cocultured allogeneic CD8(+) T cells. Furthermore, BMDCs of IL-2-deficient mice showed similarly abolished LPS-induced T cell priming as TCAIM-overexpressing wild type BMDCs. Thus, TCAIM interferes with TLR4 signaling in BMDCs and subsequently impairs their T cell priming capacity, which supports its role for tolerance induction.

Epitope-specific regulation of memory programming by differential duration of antigen presentation to influenza-specific CD8(+) T cells

Memory CD8(+) T cells are programmed during the primary response for robust secondary responsiveness. Here we show that CD8(+) T cells responding to different epitopes of influenza virus received qualitatively different signals during the primary response that altered their secondary responsiveness. Nucleoprotein (NP)-specific CD8(+) T cells encountered antigen on CD40-licensed, CD70-expressing, CD103(-)CD11b(hi) dendritic cells (DCs) at later times in the primary response. As a consequence, they maintained CD25 expression and responded to interleukin-2 (IL-2) and CD27, which together programmed their robust secondary proliferative capacity and interferon-γ (IFN-γ)-producing ability. In contrast, polymerase (PA)-specific CD8(+) T cells did not encounter antigen-bearing, CD40-activated DCs at later times in the primary response, did not receive CD27 and CD25 signals, and were not programmed to become memory CD8(+) T cells with strong proliferative and cytokine-producing ability. As a result, CD8(+) T cells responding to abundant antigens, like NP, dominated the secondary response.

T-cell-mediated immunity and the role of TRAIL in sepsis-induced immunosuppression

Sepsis is the leading cause of death in most intensive care units, and the death of septic patients usually does not result from the initial septic event but rather from subsequent nosocomial infections. Patients who survive severe sepsis often display severely compromised immune function. Not only is there significant apoptosis of lymphoid and myeloid cells that depletes critical components of the immune system during sepsis, there is also decreased function of the remaining immune cells. Studies of animals and humans suggest the immune defects that occur during sepsis may be critical to pathogenesis and subsequent mortality. This review focuses on sepsis-induced alterations with the cluster differentiation (CD) 8 T-cell compartment that can affect the control of secondary heterologous infections. Understanding how a septic event directly influences CD8 T-cell populations through apoptotic death and homeostatic proliferation and indirectly by immune-mediated suppression will provide valuable starting points for developing new treatment options.

With(out) a little help from my friends: an IL-12/CD40L-mediated feed-forward loop between CD8+ T cells and DCs

CD40-CD40L interactions are important for both antigen-dependent B-cell differentiation and effector and memory T-cell formation. The prevailing view is that CD40L is expressed on activated CD4(+) T cells, which enables them to provide help to high-affinity B cells in GCs and to license DCs for efficient induction of CD8(+) T-cell responses. Interestingly, CD8(+) T cells themselves can also express CD40L and, in this issue of the European Journal of Immunology, Thiel and colleagues [Eur. J. Immunol. 2013. 43: 1511-1517] show that CD40L expression on these cells can be part of a self-sustaining feed-forward loop, in which expression of CD40L is induced by IL-12 and TCR signaling. This provides a paradigm shift in our thinking about the requirements of effector CD8(+) T-cell development and the role herein of CD4(+) T cells to provide help in this process.

The CD4⁺ T-cell help signal is transmitted from APC to CD8⁺ T-cells via CD27-CD70 interactions

CD8(+) cytotoxic T lymphocytes are critical components of immunity against infectious pathogens, tumours, and in the case of pathogenic autoimmunity, normal self tissues. CD4(+) T (T(H)) cells provide 'help' to CD8(+) cytotoxic T lymphocytes during priming by first activating antigen-presenting cells via CD40-CD40L interactions. Here we show that, after immunization with either a noninflammatory, nonreplicating antigen or an overtly inflammatory replicating antigen, CD8(+) cytotoxic T lymphocytes prevented from receiving a signal through CD27 during priming subsequently exhibit a specific defect in their capacity for secondary expansion that can be rescued by the absence of TRAIL. Thus, the 'help message' is transmitted to CD8(+) T cells via CD70-CD27 signals, enabling them to undergo secondary expansion and avoid TRAIL-mediated apoptosis on re-stimulation. These findings complete our understanding of the cellular interactions through which T(H) is provided to CD8(+) cytotoxic T lymphocytes during priming.

Nab2 regulates secondary CD8+ T-cell responses through control of TRAIL expression

CD4(+) Th cells are pivotal for the generation and maintenance of CD8(+) T-cell responses. "Helped" CD8(+) T cells receive signals during priming that prevent the induction of the proapoptotic molecule TNF-related apoptosis-inducing ligand (TRAIL) during reactivation, thereby enabling robust secondary expansion. Conversely, "helpless" CD8(+) T cells primed in the absence of Th induce TRAIL expression after restimulation and undergo activation-induced cell death. In the present study, we investigated the molecular basis for the differential regulation of TRAIL in helped versus helpless CD8(+) T cells by comparing their transcriptional profiles, and have identified a transcriptional corepressor, NGFI-A binding protein 2 (Nab2), that is selectively induced in helped CD8(+) T cells. Enforced expression of Nab2 prevents TRAIL induction after restimulation of primary helpless CD8(+) T cells, and expression of a dominant-negative form of Nab2 in helped CD8(+) T cells impairs their secondary proliferative response that is reversible by TRAIL blockade. Finally, we observe that the CD8(+) T-cell autocrine growth factor IL-2 coordinately increases Nab2 expression and decreases TRAIL expression. These findings identify Nab2 as a mediator of Th-dependent CD8(+) T-cell memory responses through the regulation of TRAIL and the promotion of secondary expansion, and suggest a mechanism through which this operates.