ICAM-1-dependent homotypic aggregates regulate CD8 T cell effector function and differentiation during T cell activation

Sex- and species-specific contribution of CD99 to T cell costimulation during multiple sclerosis

BACKGROUND

Differences in immune responses between women and men are leading to a strong sex bias in the incidence of autoimmune diseases that predominantly affect women, such as multiple sclerosis (MS). MS manifests in more than twice as many women, making sex one of the most important risk factor. However, it is incompletely understood which genes contribute to sex differences in autoimmune incidence. To address that, we conducted a gene expression analysis in female and male human spleen and identified the transmembrane protein CD99 as one of the most significantly differentially expressed genes with marked increase in men. CD99 has been reported to participate in immune cell transmigration and T cell regulation, but sex-specific implications have not been comprehensively investigated.

METHODS

In this study, we conducted a gene expression analysis in female and male human spleen using the Genotype-Tissue Expression (GTEx) project dataset to identify differentially expressed genes between women and men. After successful validation on protein level of human immune cell subsets, we assessed hormonal regulation of CD99 as well as its implication on T cell regulation in primary human T cells and Jurkat T cells. In addition, we performed in vivo assays in wildtype mice and in Cd99-deficient mice to further analyze functional consequences of differential CD99 expression.

RESULTS

Here, we found higher CD99 gene expression in male human spleens compared to females and confirmed this expression difference on protein level on the surface of T cells and pDCs. Androgens are likely dispensable as the cause shown by in vitro assays and ex vivo analysis of trans men samples. In cerebrospinal fluid, CD99 was higher on T cells compared to blood. Of note, male MS patients had lower CD99 levels on CD4+ T cells in the CSF, unlike controls. By contrast, both sexes had similar CD99 expression in mice and Cd99-deficient mice showed equal susceptibility to experimental autoimmune encephalomyelitis compared to wildtypes. Functionally, CD99 increased upon human T cell activation and inhibited T cell proliferation after blockade. Accordingly, CD99-deficient Jurkat T cells showed decreased cell proliferation and cluster formation, rescued by CD99 reintroduction.

CONCLUSIONS

Our results demonstrate that CD99 is sex-specifically regulated in healthy individuals and MS patients and that it is involved in T cell costimulation in humans but not in mice. CD99 could potentially contribute to MS incidence and susceptibility in a sex-specific manner.

Multimodal stimulation screens reveal unique and shared genes limiting T cell fitness

Genes limiting T cell antitumor activity may serve as therapeutic targets. It has not been systematically studied whether there are regulators that uniquely or broadly contribute to T cell fitness. We perform genome-scale CRISPR-Cas9 knockout screens in primary CD8 T cells to uncover genes negatively impacting fitness upon three modes of stimulation: (1) intense, triggering activation-induced cell death (AICD); (2) acute, triggering expansion; (3) chronic, causing dysfunction. Besides established regulators, we uncover genes controlling T cell fitness either specifically or commonly upon differential stimulation. Dap5 ablation, ranking highly in all three screens, increases translation while enhancing tumor killing. Loss of Icam1-mediated homotypic T cell clustering amplifies cell expansion and effector functions after both acute and intense stimulation. Lastly, Ctbp1 inactivation induces functional T cell persistence exclusively upon chronic stimulation. Our results functionally annotate fitness regulators based on their unique or shared contribution to traits limiting T cell antitumor activity.

ICAMs in Immunity, Intercellular Adhesion and Communication

Interactions among leukocytes and leukocytes with immune-associated auxiliary cells represent an essential feature of the immune response that requires the involvement of cell adhesion molecules (CAMs). In the immune system, CAMs include a wide range of members pertaining to different structural and functional families involved in cell development, activation, differentiation and migration. Among them, β2 integrins (LFA-1, Mac-1, p150,95 and αDβ2) are predominantly involved in homotypic and heterotypic leukocyte adhesion. β2 integrins bind to intercellular (I)CAMs, actin cytoskeleton-linked receptors belonging to immunoglobulin superfamily (IgSF)-CAMs expressed by leukocytes and vascular endothelial cells, enabling leukocyte activation and transendothelial migration. β2 integrins have long been viewed as the most important ICAMs partners, propagating intracellular signalling from β2 integrin-ICAM adhesion receptor interaction. In this review, we present previous evidence from pioneering studies and more recent findings supporting an important role for ICAMs in signal transduction. We also discuss the contribution of immune ICAMs (ICAM-1, -2, and -3) to reciprocal cell signalling and function in processes in which β2 integrins supposedly take the lead, paying particular attention to T cell activation, differentiation and migration.

Annotation of CD8+ T-cell function via ICAM-1 imaging identifies FAK inhibition as an adjuvant to augment the antitumor immunity of radiotherapy

Background: Radiotherapy (RT) may trigger systemic antitumor immunity, manifesting as regression of non-irradiated lesions (abscopal effect). Intracellular adhesion molecule-1 (ICAM-1) is a key molecule involved in the abscopal effect of RT. However, the specific function of ICAM-1 in CD8+ T cells during antitumor immune responses remains unclear. Herein, we investigated whether noninvasive imaging of ICAM-1 can be used to annotate CD8+ T-cell function, thereby better selecting combinational therapy to enhance the antitumor immunity induced by RT. Methods: Using knockout mouse models, we investigated the role of ICAM-1 expressed on CD8+ T cells in the antitumor immunity of RT and conducted drug screening guided by ICAM-1-targeted noninvasive imaging. Results: The systemic antitumor effect of RT relies on the expression of ICAM-1 on CD8+ T cells. ICAM-1 expression is essential for CD8+ T-cell activation, proliferation, and effector function. Noninvasive annotation of the proliferation and effector function of CD8+ T cells by ICAM-1-targeted imaging identified VS-6063, a focal adhesion kinase inhibitor, as a new adjuvant to augment systemic antitumor immunity of RT in an immunologically "cold" tumor model. Mechanistically, VS-6063 overcomes the physical barriers in tumors and promotes the migration and infiltration of CD8+ T cells primed by RT into distant tumors. Conclusion: Our findings highlight that molecular imaging of ICAM-1 levels provides a dynamic readout of the proliferation and effector function of tumor-infiltrating CD8+ T cells, which facilitates the high-throughput exploitation of new combinational drugs to maximize the systemic antitumor effect of RT.

A near-infrared fluorescence-enhancing plasmonic biosensing microarray identifies soluble PD-L1 and ICAM-1 as predictive checkpoint biomarkers for cancer immunotherapy

Sensitive and accurate biomarker-driven assay guidance has been widely adopted to identify responsive patients for immune checkpoint blockade (ICB) therapy to impede disease progression and extend survival. However, most current assays are invasive, requiring surgical pathology specimens and only informing monochronic information. Here, we report a multiplexed enhanced fluorescence microarray immunoassay (eFMIA) based on a nanostructured gold nanoisland substrate (AuNIS), which macroscopically amplifies near-infrared fluorescence (NIRF) of a structurally symmetric IRDye78 fluorophore by over two orders of magnitude of 202.6-fold. Aided by non-contact piezo-driven micro-dispensing (PDMD), eFMIA simultaneously and semi-quantitatively detected intracellular and secreted programmed death-ligand 1 (PD-L1) and intercellular adhesion molecule-1 (ICAM-1) in human nasopharyngeal carcinoma (NPC) cells. The assay performance was superior to fluorescence immunoassays (FIA) and enzyme-linked immunosorbent assays (ELISA), with lower detection limits. Using eFMIA, we found significantly differential levels of soluble PD-L1 (sPD-L1) and sICAM-1 in the sera of 28 cancer patients, with different clinical outcomes following anti-PD-1 ICB therapy. With a well-characterized mechanism, the high-performance plasmonic multiplexed assay with the composite biomarkers may be a valuable tool to assist clinicians with decision-making and patient stratification to afford predictive ICB therapy responses.

Intracellular Adhesion Molecule-1 Improves Responsiveness to Immune Checkpoint Inhibitor by Activating CD8+ T Cells

Immune checkpoint inhibitor (ICI) clinically benefits cancer treatment. However, the ICI responses are only achieved in a subset of patients, and the underlying mechanisms of the limited response remain unclear. 160 patients with non-small cell lung cancer treated with anti-programmed cell death protein-1 (anti-PD-1) or anti-programmed death ligand-1 (anti-PD-L1) are analyzed to understand the early determinants of response to ICI. It is observed that high levels of intracellular adhesion molecule-1 (ICAM-1) in tumors and plasma of patients are associated with prolonged survival. Further reverse translational studies using murine syngeneic tumor models reveal that soluble ICAM-1 (sICAM-1) is a key molecule that increases the efficacy of anti-PD-1 via activation of cytotoxic T cells. Moreover, chemokine (CXC motif) ligand 13 (CXCL13) in tumors and plasma is correlated with the level of ICAM-1 and ICI efficacy, suggesting that CXCL13 might be involved in the ICAM-1-mediated anti-tumor pathway. Using sICAM-1 alone and in combination with anti-PD-1 enhances anti-tumor efficacy in anti-PD-1-responsive tumors in murine models. Notably, combinatorial therapy with sICAM-1 and anti-PD-1 converts anti-PD-1-resistant tumors to responsive ones in a preclinical study. These findings provide a new immunotherapeutic strategy for treating cancers using ICAM-1.

Exhausted T cells hijacking the cancer-immunity cycle: Assets and liabilities

T cell exhaustion is an alternative differentiation path of T cells, sometimes described as a dysfunction. During the last decade, insights of T cell exhaustion acting as a bottle neck in the field of cancer immunotherapy have undoubtedly provoked attention. One of the main drivers of T cell exhaustion is prolonged antigen presentation, a prerequisite in the cancer-immunity cycle. The umbrella term "T cell exhaustion" comprises various stages of T cell functionalities, describing the dynamic, one-way exhaustion process. Together these qualities of T cells at the exhaustion continuum can enable tumor clearance, but if the exhaustion acquired timeframe is exceeded, tumor cells have increased possibilities of escaping immune system surveillance. This could be considered a tipping point where exhausted T cells switch from an asset to a liability. In this review, the contrary role of exhausted T cells is discussed.

Single-Cell RNA-Sequencing Reveals Interactions between Endometrial Stromal Cells, Epithelial Cells, and Lymphocytes during Mouse Embryo Implantation

The decidualization of endometrial stromal cells (ESCs) is an essential process facilitating embryo implantation. However, the roles of non-decidualized and decidualized ESCs in regulating the microenvironment of a receptive endometrium remain unclear. We investigated single-cell transcriptomic changes in the uterus of a CD-1 mouse model at the post-implantation stage. The implantation and inter-implantation sites of the uteruses of pregnant mice at 4.5 and 5.5 days post-coitum were dissected for single-cell RNA sequencing. We identified eight cell types: epithelial cells, stromal cells, endothelial cells, mesothelial cells, lymphocytes, myocytes, myeloids, and pericytes. The ESC transcriptome suggests that the four ESC subtypes are involved in the extracellular remodeling during implantation. The trajectory plot of ESC subtypes indicates embryo implantation that involves a differentiation pathway from undifferentiated ESCs (ESC 1) to decidualized ESCs (DEC ESCs), with distinct signaling pathways between the ESC subtypes. Furthermore, the ligand-receptor analysis suggests that ESCs communicate with epithelial cells and immune cells through nectin and ICAM signaling. Collectively, both decidualized and non-decidualized ESCs may regulate the endometrial microenvironment for optimal endometrial receptivity and immune tolerance. This study provides insights on the molecular and cellular characteristics of mouse ESCs in modulating the epithelial and lymphocyte functions during early embryo implantation.

Roles of intercellular cell adhesion molecule-1 (ICAM-1) in colorectal cancer: expression, functions, prognosis, tumorigenesis, polymorphisms and therapeutic implications

Colorectal cancer (CRC) is a major global health problem and one of the major causes of cancer-related death worldwide. It is very important to understand the pathogenesis of CRC for early diagnosis, prevention strategies and identification of new therapeutic targets. Intercellular adhesion molecule-1 (ICAM-1, CD54) displays an important role in the the pathogenesis of CRC. It is a cell surface glycoprotein of the immunoglobulin (Ig) superfamily and plays an essential role in cell-cell, cell-extracellular matrix interaction, cell signaling and immune process. It is also expressed by tumor cells and modulates their functions, including apoptosis, cell motility, invasion and angiogenesis. The interaction between ICAM-1 and its ligand may facilitate adhesion of tumor cells to the vascular endothelium and subsequently in the promotion of metastasis. ICAM-1 expression determines malignant potential of cancer. In this review, we will discuss the expression, function, prognosis, tumorigenesis, polymorphisms and therapeutic implications of ICAM-1 in CRC.

IFNγ-primed periodontal ligament cells regulate T-cell responses via IFNγ-inducible mediators and ICAM-1-mediated direct cell contact

Periodontal ligament (PDL) cells help maintain tissue homeostasis by balancing PDL tissue inflammation and regeneration. However, the mechanisms by which interferon γ (IFNγ) modulate this process are not yet fully understood. The present study aimed to examine the effect of primed and non-primed PDL cells with IFNγ on the viability and differentiation of T lymphocytes and its functional consequences. The results showed that IFNγ-primed PDL cells possessed enhanced immunosuppression by suppressing T-lymphocyte viability and directing T-lymphocyte differentiation towards a higher T helper (Th) Th2/Th1 ratio. Suppression of T-cell viability was mainly mediated by IFNγ-inducible secreted mediators, which was prevented in the presence of direct cell contact, probably by intercellular adhesion molecule-1 (ICAM-1)-induced PI3 K-mediated transforming growth factor β1 expression in PDL cells. By contrast, ICAM-1 activation augmented IFNγ-induced IFNγ and interleukin-6 expression in PDL cells, which in turn modulated T-cell differentiation. The resulting interaction between these two cell types activated macrophage and suppressed osteoclast differentiation. In conclusion, the results have shown, for the first time to our knowledge, that primed and non-primed PDL cells with IFNγ differentially control T-cell responses via IFNγ-inducible mediators and ICAM-1-mediated direct cell contact, suggesting the role of PDL cells in shifting an inflammatory phase towards a regenerative phase.

Healing Field: Using Alternating Electric Fields to Prevent Cytokine Storm by Suppressing Clonal Expansion of the Activated Lymphocytes in the Blood Sample of the COVID-19 Patients

In the case of the COVID-19 early diagnosis, numerous tech innovations have been introduced, and many are currently employed worldwide. But, all of the medical procedures for the treatment of this disease, up to now, are just limited to chemical drugs. All of the scientists believe that the major challenge toward the mortality of the COVID-19 patients is the out-of-control immune system activation and the subsequent cytokine production. During this process, the adaptive immune system is highly activated, and many of the lymphocytes start to clonally expand; hence many cytokines are also released. So, any attempt to harness this cytokine storm and calm down the immune outrage is appreciated. While the battleground for the immune hyperactivation is the lung ambient of the infected patients, the only medical treatment for suppressing the hypercytokinemia is based on the immunosuppressor drugs that systemically dampen the immunity with many unavoidable side effects. Here, we applied the alternating electric field to suppress the expansion of the highly activated lymphocytes, and by reducing the number of the renewed cells, the produced cytokines were also decreased. Applying this method to the blood of the COVID-19 patients in vitro showed ∼33% reduction in the average concentration of the three main cytokines after 4 days of stimulation. This method could carefully be utilized to locally suppress the hyperactivated immune cells in the lung of the COVID-19 patients without any need for systemic suppression of the immune system by the chemical drugs.

Roles of the tissue-type plasminogen activator in immune response

The COVID-19 pandemic has once again brought to the forefront the existence of a tight link between the coagulation/fibrinolytic system and the immunologic processes. Tissue-type plasminogen activator (tPA) is a serine protease with a key role in fibrinolysis by converting plasminogen into plasmin that can finally degrade fibrin clots. tPA is released in the blood by endothelial cells and hepatocytes but is also produced by various types of immune cells including T cells and monocytes. Beyond its role on hemostasis, tPA is also a potent modulator of inflammation and is involved in the regulation of several inflammatory diseases. Here, after a brief description of tPA structure, we review its new functions in adaptive immunity focusing on T cells and antigen presenting cells. We intend to synthesize the recent knowledge on proteolysis- and receptor-mediated effects of tPA on immune response in physiological and pathological context.

LFA-1 in T cell priming, differentiation, and effector functions

The integrin LFA-1 is crucial for T cell entry into mammalian lymph nodes and tissues, and for promoting interactions with antigen-presenting cells (APCs). However, it is increasingly evident that LFA-1 has additional key roles beyond the mere support of adhesion between T cells, the endothelium, and/or APCs. These include roles in homotypic T cell-T cell (T-T) communication, the induction of intracellular complement activity underlying Th1 effector cell polarization, and the support of long-lasting T cell memory. Here, we briefly summarize current knowledge of LFA-1 biology, discuss novel cytoskeletal regulators of LFA-1 functions, and review new aspects of LFA-1 mechanobiology that are relevant to its function in immunological synapses and in specific pathologies arising from LFA-1 dysregulation.

Junctional adhesion molecule-A on dendritic cells regulates Th1 differentiation

The junctional adhesion molecule-A (JAM-A) is an adhesion molecule present in the surface of several cell types, such as endothelial cells and leukocytes as well as Dendritic Cells (DC). Given the potential relevance of JAM-A in diverse pathological conditions such as inflammatory diseases and cancer, we investigated the role of JAM-A in CD4+ T cell priming. We demonstrate that JAM-A is present in the immunological synapse formed between T cells and DC during priming. Furthermore, an antagonistic anti-JAM-A mAb could disrupt the interaction between CD4+ T cell and DC. Antagonism of JAM-A also attenuated T cell activation and proliferation with a decrease in T-bet expression and increased IL-6 and IL-17 secretion. These findings demonstrate a functional role for JAM-A in interactions between CD4+ T cells and DCs during T cell priming as a positive regulator of Th1 differentiation.

Homotypic aggregates contribute to heterogeneity in B cell fates due to an intrinsic gradient of stimulant exposure

Monocultures of several cell types result in the formation of robust clusters called homotypic aggregates (HAs). How this physical aggregation affects cell fates in immune cell cultures, is poorly understood. We studied anti-CD40-stimulated primary B cell cultures, where cells assembled into large three-dimensional LFA1-driven HAs by 72 h. The dense packing in these aggregates restricts the infiltration of stimulants, such as antibodies, to cells inside the clusters. This creates a concentration gradient of stimulant availability across the cross-section of HAs. We describe a method to retain this positional information even after the disruption of HAs, for analysis by flow cytometry. Comparison of stage-specific cell-surface markers showed that the extent of stimulant-binding affected multiple fates non-uniformly. While germinal center and lineage markers were moderately upregulated, immunoglobulins and markers associated with memory were more than doubled in the peripheral cells binding more anti-CD40. These cells also experienced a strong repression of the plasma cell regulator Prdm1 and an upregulation of the oncogene Myc. Thus, cells at different locations in HAs are subjected to unequal doses of stimulants, leading to a hitherto unreported source of heterogeneity in cell fates. These findings can be extrapolated to understand the dose-dependent effects of stimulants in other three-dimensional cell clusters.

PD-1 and LAG-3 blockade improve anti-tumor vaccine efficacy

Concurrent blockade of different checkpoint receptors, notably PD-1 and CTLA-4, elicits greater anti-tumor activity for some tumor types, and the combination of different checkpoint receptor inhibitors is an active area of clinical research. We have previously demonstrated that anti-tumor vaccination, by activating CD8 + T cells, increases the expression of PD-1, CTLA-4, LAG-3 and other inhibitory receptors, and the anti-tumor efficacy of vaccination can be increased with checkpoint blockade. In the current study, we sought to determine whether anti-tumor vaccination might be further improved with combined checkpoint blockade. Using an OVA-expressing mouse tumor model, we found that CD8 + T cells activated in the presence of professional antigen presenting cells (APC) expressed multiple checkpoint receptors; however, T cells activated without APCs expressed LAG-3 alone, suggesting that LAG-3 might be a preferred target in combination with vaccination. Using three different murine tumor models, and peptide or DNA vaccines targeting three tumor antigens, we assessed the effects of vaccines with blockade of PD-1 and/or LAG-3 on tumor growth. We report that, in each model, the anti-tumor efficacy of vaccination was increased with PD-1 and/or LAG-3 blockade. However, combined PD-1 and LAG-3 blockade elicited the greatest anti-tumor effect when combined with vaccination in a MycCaP prostate cancer model in which PD-1 blockade alone with vaccination targeting a “self” tumor antigen had less efficacy. These results suggest anti-tumor vaccination might best be combined with concurrent blockade of both PD-1 and LAG-3, and potentially other checkpoint receptors whose expression is increased on CD8 + T cells following vaccine-mediated activation.

Eomes-Dependent Loss of the Co-activating Receptor CD226 Restrains CD8+ T Cell Anti-tumor Functions and Limits the Efficacy of Cancer Immunotherapy

CD8⁺ T cells within the tumor microenvironment (TME) are exposed to various signals that ultimately determine functional outcomes. Here, we examined the role of the co-activating receptor CD226 (DNAM-1) in CD8⁺ T cell function. The absence of CD226 expression identified a subset of dysfunctional CD8⁺ T cells present in peripheral blood of healthy individuals. These cells exhibited reduced LFA-1 activation, altered TCR signaling, and a distinct transcriptomic program upon stimulation. CD226^neg CD8⁺ T cells accumulated in human and mouse tumors of diverse origin through an antigen-specific mechanism involving the transcriptional regulator Eomesodermin (Eomes). Despite similar expression of co-inhibitory receptors, CD8⁺ tumor-infiltrating lymphocyte failed to respond to anti-PD-1 in the absence of CD226. Immune checkpoint blockade efficacy was hampered in Cd226^-/- mice. Anti-CD137 (4-1BB) agonists also stimulated Eomes-dependent CD226 loss that limited the anti-tumor efficacy of this treatment. Thus, CD226 loss restrains CD8⁺ T cell function and limits the efficacy of cancer immunotherapy.

ICAM-1 orchestrates the abscopal effect of tumor radiotherapy

Compelling evidence indicates that radiotherapy (RT) has a systemic inhibitory effect on nonirradiated lesions (abscopal effect) in addition to the ablation of irradiated tumors. However, this effect occurs only in rare circumstances in clinical practice, and mechanisms underlying the abscopal effect of RT are neither fully understood nor therapeutically utilized. Here we identified that intercellular adhesion molecule-1 (ICAM-1), an inducible glycoprotein of the immunoglobulin superfamily, is up-regulated in nonirradiated tumors responsive to RT. ICAM-1 expression in preclinical animal models can be noninvasively detected by optical imaging and positron emission tomography (PET) using near-infrared fluorescence dye- and 64Cu-labeled imaging probes that we synthesized, respectively. Importantly, the expression levels of ICAM-1 determined by quantitative PET imaging showed a strong negative linear correlation with the growth of nonirradiated tumors. Moreover, genetic or pharmacologic up-regulation of ICAM-1 expression by either an intratumoral injection of engineered recombinant adenovirus or systemic administration of a Toll-like receptor 7 agonist-capsulated nanodrug could induce markedly increased abscopal responses to local RT in animal models. Mechanistic investigation revealed that ICAM-1 expression can enhance both the activation and tumor infiltration of CD8+ T cells to improve the responses of the nonirradiated tumors to RT. Together, our findings suggest that noninvasive PET imaging of ICAM-1 expression could be a powerful means to predict the responses of nonirradiated tumors to RT, which could facilitate the exploration of new combination RT strategies for effective ablation of primary and disseminated lesions.

The Effect of Nintedanib on T-Cell Activation, Subsets and Functions

Background

T cells are important regulators of inflammation and, via release of mediators, can contribute to pulmonary fibrosis. Nintedanib is approved for the treatment of idiopathic pulmonary fibrosis, systemic sclerosis-associated interstitial lung disease (ILD) and chronic fibrosing ILDs with a progressive phenotype. However, how nintedanib targets T cells has not been elucidated.

Materials and Methods

We investigated the immunomodulatory effects of nintedanib on T cells and peripheral blood mononuclear cells isolated from healthy donors. Cells were pre-incubated with different concentrations of nintedanib and then stimulated for 24 hours with anti-CD3 with or without anti-CD28 and with or without different cytokines. Levels of interferon gamma (IFN-γ), interleukin (IL)-2, IL-4, IL-5, IL-10, IL-12p70 and IL-13 were quantitated. Western blotting with primary antibodies against phospho-Lck-Y394, phospho-Lck-Y505, Lck-total and Cofilin examined the phosphorylation level of the Lck protein. In vitro T-cell proliferation, T-cell clustering and different T-cell populations were also assessed.

Results

Nintedanib blocked T-cell activation through inhibiting Lck-Y394 phosphorylation. Pretreatment of T cells with nintedanib reduced cluster formation as a marker of activation and inhibited the release of IFN-γ, IL-2, IL-4, IL-5, IL-10, IL-12p70 and IL-13 at clinically relevant concentrations ranging from 5–77 nmol/L. Nintedanib did not alter T-cell proliferation or numbers of CD4+ and CD8+ T cells, but did increase stimulated Th17-like cells without increasing IL-17A levels.

Conclusion

These immunomodulatory effects may further explain how nintedanib slows the progression of pulmonary fibrosis in various ILDs.

Upregulated ethanolamine phospholipid synthesis via selenoprotein I is required for effective metabolic reprogramming during T cell activation

OBJECTIVE

T cell activation triggers metabolic reprogramming to meet increased demands for energy and metabolites required for cellular proliferation. Ethanolamine phospholipid synthesis has emerged as a regulator of metabolic shifts in stem cells and cancer cells, which led us to investigate its potential role during T cell activation.

METHODS

As selenoprotein I (SELENOI) is an enzyme participating in two metabolic pathways for the synthesis of phosphatidylethanolamine (PE) and plasmenyl PE, we generated SELENOI-deficient mouse models to determine loss-of-function effects on metabolic reprogramming during T cell activation. Ex vivo and in vivo assays were carried out along with metabolomic, transcriptomic, and protein analyses to determine the role of SELENOI and the ethanolamine phospholipids synthesized by this enzyme in cell signaling and metabolic pathways that promote T cell activation and proliferation.

RESULTS

SELENOI knockout (KO) in mouse T cells led to reduced de novo synthesis of PE and plasmenyl PE during activation and impaired proliferation. SELENOI KO did not affect T cell receptor signaling, but reduced activation of the metabolic sensor AMPK. AMPK was inhibited by high [ATP], consistent with results showing SELENOI KO causing ATP accumulation, along with disrupted metabolic pathways and reduced glycosylphosphatidylinositol (GPI) anchor synthesis/attachment CONCLUSIONS: T cell activation upregulates SELENOI-dependent PE and plasmenyl PE synthesis as a key component of metabolic reprogramming and proliferation.

An Efficient Culture Method of CD3-Positive T Cells from Human Cryopreserved Buffy Coat Specimens

Context: In the National Cerebral and Cardiovascular Center (NCVC) Biobank, buffy coats have been collected from patients and stored with cryoprotective agents as a possible source for viable blood cells, using cost-efficient methods for storage. However, whether viable cells for in vitro studies can be recovered from these biospecimens has not been verified. Objective: To investigate whether T cells can be collected and expanded as viable cells from cryopreserved human buffy coats. Design: After thawing of cryopreserved buffy coat specimens, CD3-positive cells were isolated from the cell suspension using a leukocyte separation filter coated with an anti-CD3 antibody, and the filter-attached cells were cultured in T cell culture medium. To analyze the characteristics of these cultured cells, histocytological analyses of Giemsa staining, immunocytochemical (ICC) staining for CD3, and flow cytometry for CD3 in live cells were conducted. Results: A few days after starting cell culture, cell clusters were observed, and they gradually grew in size. Using Giemsa staining, the expanded cells were found to be ∼15 μm in diameter, having round nuclei, a high nucleus/cytoplasm ratio, and cytoplasm stained light blue, which is characteristic of lymphocytes. From ICC staining, these cells were CD3 positive, a pan-T cell marker among lymphocytes. Furthermore, CD3 immunoreactivity in live cells was detected in a flow cytometry assay, though that for CD19 was not detected, which is a marker of pan-B cells. Conclusions: These results suggest that T cells can be expanded from buffy coats cryopreserved at -180°C as an adequate method of NCVC Biobank, highlighting these biospecimens as a possible useful source for future in vitro studies.

Skin sensitization to fragrance hydroperoxides: interplay between dendritic cells, keratinocytes and free radicals

BACKGROUND

Skin sensitization to hydroperoxides (R-OOHs) of the commonly used fragrance terpenes limonene, linalool and citronellol is frequently reported. R-OOHs are believed to initiate the process leading to sensitization and allergic contact dermatitis through mechanisms involving radical intermediates. Thus, radical intermediates, keratinocytes and dendritic cells (DCs) may act in concert to initiate the process.

OBJECTIVES

To evaluate individual DC activation profiles by R-OOHs in the context of keratinocytes with regard to frequency, specificity and magnitude of upregulation.

METHODS

We used 2D and 3D cocultures with keratinocytes/reconstructed human epidermis (RHE) and DCs to evaluate cell surface levels of the costimulatory molecules CD86, CD80 and the adhesion molecule CD54 on cocultured DCs. Analysis of radical formation from limonene hydroperoxides in RHE was performed using electron paramagnetic resonance combined with the spin trapping technique.

RESULTS

R-OOHs induce donor-dependent DC activation. Major differences were found between the limonene-OOHs. Limonene-1-OOH was stronger with respect to both frequency and magnitude of response. Using a 3D coculture model, no DC activation was detected after topical application of 0·2% limonene-OOHs (20 µg cm^-2 ), while 1·2% limonene-1-OOH or 2% limonene-2-OOH induced DC activation. Furthermore, we demonstrated differences in the carbon and oxygen radicals formed from the limonene-OOHs using RHE, mimicking what may happen in vivo.

CONCLUSIONS

We report clear individual differences in DC maturation induced by the most important hydroperoxides. Response rates and magnitude of response both indicate that very small structural alterations in the hydroperoxides are translated into specific DC responses. In addition, we provide more insight into the amounts of hydroperoxides that can activate DCs and induce sensitization.

Development and characterization of CD54-targeted immunoPET imaging in solid tumors

PURPOSE

Intercellular adhesion molecule-1 (ICAM-1, CD54) is an emerging therapeutic target for a variety of solid tumors including melanoma and anaplastic thyroid cancer (ATC). This study aims to develop an ICAM-1-targeted immuno-positron emission tomography (immunoPET) imaging strategy and assess its diagnostic value in melanoma and ATC models.

METHODS

Flow cytometry was used to screen ICAM-1-positive melanoma and ATC cell lines. Melanoma and ATC models were established using A375 cell line and THJ-16T cell line, respectively. An ICAM-1-specific monoclonal antibody (R6-5-D6) and a nonspecific human IgG were radiolabeled with ⁶⁴Cu and the diagnostic efficacies were interrogated in tumor-bearing mouse models. Biodistribution and fluorescent imaging studies were performed to confirm the specificity of the ICAM-1-targeted imaging probes.

RESULTS

ICAM-1 was strongly expressed on melanoma and advanced thyroid cancer cell lines. ⁶⁴Cu-NOTA-ICAM-1 immunoPET imaging efficiently delineated A375 melanomas with a peak tumor uptake of 21.28 ± 6.56 %ID/g (n = 5), significantly higher than that of ⁶⁴Cu-NOTA-IgG (10.63 ± 2.58 %ID/g, n = 3). Moreover, immunoPET imaging with ⁶⁴Cu-NOTA-ICAM-1 efficiently visualized subcutaneous and orthotopic ATCs with high clarity and contrast. Fluorescent imaging with IRDye 800CW-ICAM-1 also visualized orthotopic ATCs and the tumor uptake could be blocked by the ICAM-1 parental antibody R6-5-D6, indicating the high specificity of the developed probe. Finally, blocking with the human IgG prolonged the circulation of the ⁶⁴Cu-NOTA-ICAM-1 in R2G2 mice without compromising the tumor uptake.

CONCLUSION

ICAM-1-targeted immunoPET imaging could characterize ICAM-1 expression in melanoma and ATC, which holds promise for optimizing ICAM-1-targeted therapies in the future.

Modes of Communication between T Cells and Relevance for Immune Responses

T cells are essential mediators of the adaptive immune system, which constantly patrol the body in search for invading pathogens. During an infection, T cells that recognise the pathogen are recruited, expand and differentiate into subtypes tailored to the infection. In addition, they differentiate into subsets required for short and long-term control of the pathogen, i.e., effector or memory. T cells have a remarkable degree of plasticity and heterogeneity in their response, however, their overall response to a given infection is consistent and robust. Much research has focused on how individual T cells are activated and programmed. However, in order to achieve a critical level of population-wide reproducibility and robustness, neighbouring cells and surrounding tissues have to provide or amplify relevant signals to tune the overall response accordingly. The characteristics of the immune response-stochastic on the individual cell level, robust on the global level-necessitate coordinated responses on a system-wide level, which facilitates the control of pathogens, while maintaining self-tolerance. This global coordination can only be achieved by constant cellular communication between responding cells, and faults in this intercellular crosstalk can potentially lead to immunopathology or autoimmunity. In this review, we will discuss how T cells mount a global, collective response, by describing the modes of T cell-T cell (T-T) communication they use and highlighting their physiological relevance in programming and controlling the T cell response.

Closed loop bioreactor system for the ex vivo expansion of human T cells

BACKGROUND AIM

Translation of therapeutic cell therapies to clinical-scale products is critical to realizing widespread success. Currently, however, there are limited tools that are accessible at the research level and readily scalable to clinical-scale needs.

METHODS

We herein developed and assessed a closed loop bioreactor system in which (i) a highly gas-permeable silicone material was used to fabricate cell culture bags and (ii) dynamic flow was introduced to allow for dissociation of activated T-cell aggregates.

RESULTS

Using this system, we find superior T-cell proliferation compared with conventional bag materials and flasks, especially at later time points. Furthermore, intermittent dynamic flow could easily break apart T-cell clusters.

CONCLUSIONS

Our novel closed loop bioreactor system is amenable to enhanced T-cell proliferation and has broader implications for being easily scaled for use in larger need settings.

Paracrine costimulation of IFN-γ signaling by integrins modulates CD8 T cell differentiation

The cytokine IFN-γ is a critical regulator of immune system development and function. Almost all leukocytes express the receptor for IFN-γ, yet each cell type elicits a different response to this cytokine. Cell type-specific effects of IFN-γ make it difficult to predict the outcomes of the systemic IFN-γ blockade and limit its clinical application, despite many years of research. To better understand the cell-cell interactions and cofactors that specify IFN-γ functions, we focused on the function of IFN-γ on CD8 T cell differentiation. We demonstrated that during bacterial infection, IFN-γ is a dominant paracrine trigger that skews CD8 T cell differentiation toward memory. This skewing is preferentially driven by contact-dependent T cell-T cell (T-T) interactions and the localized IFN-γ secretion among activated CD8 T cells in a unique splenic microenvironment, and is less sensitive to concurrent IFN-γ production by other immune cell populations such as natural killer (NK) cells. Modulation of CD8 T cell differentiation by IFN-γ relies on a nonconventional IFN-γ outcome that occurs specifically within 24 hours following infection. This is driven by IFN-γ costimulation by integrins at T-T synapses, and leads to synergistic phosphorylation of the proximal STAT1 molecule and accelerated IL-2 receptor down-regulation. This study provides evidence of the importance of context-dependent cytokine signaling and gives another example of how cell clusters and the microenvironment drive unique biology.

ICAM-1-LFA-1 Dependent CD8+ T-Lymphocyte Aggregation in Tumor Tissue Prevents Recirculation to Draining Lymph Nodes

The quantity of T-lymphocytes reaching the draining lymph nodes from tumors is likely important to mount effective distant responses and for the establishment of long term systemic memory. Looking into mechanisms behind lymphocyte egress, we directed our attention to leukocyte adhesion mechanisms inside tumors. Here we demonstrate that activated T-cells form intra-tumor aggregates in a LFA-1-ICAM-1-dependent fashion in mouse models of melanoma and breast cancer. We also provide evidence of the presence of T-cell clusters in primary human melanoma. Disruption of LFA-1-ICAM-1 interactions, and thereby T-cell clustering, enhances the arrival of activated CD8+ T-cells to tumor draining lymph nodes in both transplanted and spontaneous cancer models. Interestingly, upon ICAM-1 blockade, the expression of the chemotactic receptor CCR7 augments in tumor infiltrating lymphocytes and in in-vitro de-clustered T cells, as well as their ability to transmigrate across lymphatic endothelial cells. We propose that ICAM-1-mediated homotypic T-lymphocyte aggregation may serve as a tumor-mediated immune retention mechanism entrapping activated CD8+ T cells in the tumor microenvironment. Modulation of T-cell adhesion may be of use to improve the transit of activated lymphocytes toward the lymph nodes and their subsequent recirculation.

LFA-1 Ligation by High-Density ICAM-1 Is Sufficient To Activate IFN-γ Release by Innate T Lymphocytes

By binding to its ligand ICAM-1, LFA-1 is known to mediate both adhesion and costimulatory signaling for T cell activation. The constitutively high LFA-1 cell surface expression of invariant NKT (iNKT) cells has been shown to be responsible for their distinctive tissue homing and residency within ICAM-rich endothelial vessels. However, the functional impact of LFA-1 on the activation of iNKT cells and other innate T lymphocyte subsets has remained largely unexplored. In particular, it is not clear whether LFA-1 contributes to innate-like pathways of T cell activation, such as IFN-γ secretion in response to IL-12. Using a recombinant ICAM-1-Fc fusion protein to stimulate human iNKT cells in the absence of APCs, we show that LFA-1 engagement enhances their IL-12-driven IFN-γ production. Surprisingly, exposure to high densities of ICAM-1 was also sufficient to activate iNKT cell cytokine secretion independently of IL-12 and associated JAK/STAT signaling. LFA-1 engagement induced elevated cytoplasmic Ca²⁺ and rapid ERK phosphorylation in iNKT cells, and the resulting IFN-γ secretion was dependent on both of these pathways. Analysis of freshly isolated human PBMC samples revealed that a fraction of lymphocytes that showed elevated LFA-1 cell surface expression produced IFN-γ in response to plate-bound ICAM-1-Fc. A majority of the responding cells were T cells, with the remainder NK cells. The responding T cells included iNKT cells, MAIT cells, and Vδ2⁺ γδ T cells. These results delineate a novel integrin-mediated pathway of IFN-γ secretion that is a shared feature of innate lymphocytes.

Expansion and Antitumor Cytotoxicity of T-Cells Are Augmented by Substrate-Bound CCL21 and Intercellular Adhesion Molecule 1

Adoptive immunotherapy is based on ex vivo expansion and stimulation of T-cells, followed by their transfer into patients. The need for the ex vivo culturing step provides opportunities for modulating the properties of transferred T-cells, enhancing their antitumor abilities, and increasing their number. Here, we present a synthetic immune niche (SIN) that increases the number and antitumor activity of cytotoxic CD8⁺ T-cells. We first evaluated the effect of various SIN compositions that mimic the physiological microenvironment encountered by T-cells during their activation and expansion in the lymph node. We found that substrates coated with the chemokine CCL21 together with the adhesion molecule intercellular adhesion molecule 1 significantly increase the number of ovalbumin-specific murine CD8⁺ T-cells activated by antigen-loaded dendritic cells or activation microbeads. Notably, cells cultured on these substrates also displayed augmented cytotoxic activity toward ovalbumin-expressing melanoma cells, both in culture and in vivo. This increase in specific cytotoxic activity was associated with a major increase in the cellular levels of the killing-mediator granzyme B. Our results suggest that this SIN may be used for generating T-cells with augmented cytotoxic function, for use in cancer immunotherapy.

Exposure of Human CD8+ T Cells to Type-2 Cytokines Impairs Division and Differentiation and Induces Limited Polarization

Effector CD8+ T cells generally produce type-1 cytokines and mediators of the perforin/granzyme cytolytic pathway, yet type-2-polarized CD8+ cells (Tc2) are detected in type-2 (T2) cytokine-driven diseases such as asthma. It is unclear whether T2 cytokine exposure during activation is sufficient to polarize human CD8+ T cells. To address this question, a protocol was developed for high-efficiency activation of human CD8+ T cells in which purified single cells or populations were stimulated with plate-bound anti-CD3 and anti-CD11a mAb for up to 8 days in T2 polarizing or neutral conditions, before functional analysis. Activation of CD8+ naïve T cells (TN) in T2 compared with neutral conditions decreased the size of single-cell clones, although early division kinetics were equivalent, indicating an effect on overall division number. Activation of TN in T2 conditions followed by brief anti-CD3 mAb restimulation favored expression of T2 cytokines, GATA3 and Eomes, and lowered expression of type-1 cytokines, Prf1, Gzmb, T-BET, and Prdm1. However, IL-4 was only weakly expressed, and PMA and ionomycin restimulation favored IFN-γ over IL-4 expression. Activation of TN in T2 compared with neutral conditions prevented downregulation of costimulatory (CD27, CD28) and lymph-node homing receptors (CCR7) and CD95 acquisition, which typically occur during differentiation into effector phenotypes. CD3 was rapidly and substantially induced after activation in neutral, but not T2 conditions, potentially contributing to greater division and differentiation in neutral conditions. CD8+ central memory T cells (TCM) were less able to enter division upon reactivation in T2 compared with neutral conditions, and were more refractory to modulating IFN-γ and IL-4 production than CD8+ TN. In summary, while activation of TN in T2 conditions can generate T2 cytokine-biased cells, IL-4 expression is weak, T2 bias is lost upon strong restimulation, differentiation, and division are arrested, and reactivation of TCM is reduced in T2 conditions. Taken together, this suggests that exposure to T2 cytokines during activation may not be sufficient to generate and retain human Tc2 cells.

LFA-1 in T Cell Migration and Differentiation

Maintenance of homeostatic immune surveillance and development of effective adaptive immune responses require precise regulation of spatial and temporal lymphocyte trafficking throughout the body to ensure pathogen clearance and memory generation. Dysregulation of lymphocyte activation and migration can lead to impaired adaptive immunity, recurrent infections, and an array of autoimmune diseases and chronic inflammation. Central to the recruitment of T cells, integrins are cell surface receptors that regulate adhesion, signal transduction, and migration. With 24 integrin pairs having been discovered to date, integrins are defined not only by the composition of the heterodimeric pair but by cell-type specific expression and their ligands. Furthermore, integrins not only facilitate adhesion but also induce intracellular signaling and have recently been uncovered as mechanosensors providing additional complexity to the signaling pathways. Among several leukocyte-specific integrins, lymphocyte function-associated antigen-1 (LFA-1 or α_Lβ₂; CD11a/CD18) is a key T cell integrin, which plays a major role in regulating T cell activation and migration. Adhesion to LFA-1's ligand, intracellular adhesion receptor 1 (ICAM-1) facilitates firm endothelium adhesion, prolonged contact with antigen-presenting cells, and binding to target cells for killing. While the downstream signaling pathways utilized by LFA-1 are vastly conserved they allow for highly disparate responses. Here, we summarize the roles of LFA-1 and ongoing studies to better understand its functions and regulation.

Cancer vaccine formulation dictates synergy with CTLA-4 and PD-L1 checkpoint blockade therapy

Anticancer vaccination is a promising approach to increase the efficacy of cytotoxic T lymphocyte-associated protein 4 (CTLA-4) and programmed death ligand 1 (PD-L1) checkpoint blockade therapies. However, the landmark FDA registration trial for anti-CTLA-4 therapy (ipilimumab) revealed a complete lack of benefit of adding vaccination with gp100 peptide formulated in incomplete Freund's adjuvant (IFA). Here, using a mouse model of melanoma, we found that gp100 vaccination induced gp100-specific effector T cells (Teffs), which dominantly forced trafficking of anti-CTLA-4-induced, non-gp100-specific Teffs away from the tumor, reducing tumor control. The inflamed vaccination site subsequently also sequestered and destroyed anti-CTLA-4-induced Teffs with specificities for tumor antigens other than gp100, reducing the antitumor efficacy of anti-CTLA-4 therapy. Mechanistically, Teffs at the vaccination site recruited inflammatory monocytes, which in turn attracted additional Teffs in a vicious cycle mediated by IFN-γ, CXCR3, ICAM-1, and CCL2, dependent on IFA formulation. In contrast, nonpersistent vaccine formulations based on dendritic cells, viral vectors, or water-soluble peptides potently synergized with checkpoint blockade of both CTLA-4 and PD-L1 and induced complete tumor regression, including in settings of primary resistance to dual checkpoint blockade. We conclude that cancer vaccine formulation can dominantly determine synergy, or lack thereof, with CTLA-4 and PD-L1 checkpoint blockade therapy for cancer.

Reversible Transgene Expression Reduces Fratricide and Permits 4-1BB Costimulation of CAR T Cells Directed to T-cell Malignancies

T cells expressing second-generation chimeric antigen receptors (CARs) specific for CD5, a T-cell surface marker present on normal and malignant T cells, can selectively kill tumor cells. We aimed to improve this killing by substituting the CD28 costimulatory endodomain (28.z) with 4-1BB (BB.z), as 28.z CD5 CAR T cells rapidly differentiated into short-lived effector cells. In contrast, 4-1BB costimulation is known to promote development of the central memory subpopulation. Here, we found BB.z CD5 CAR T cells had impaired growth compared with 28.z CD5.CAR T cells, due to increased T-cell-T-cell fratricide. We demonstrate that TRAF signaling from the 4-1BB endodomain upregulated the intercellular adhesion molecule 1, which stabilized the fratricidal immunologic synapse between CD5 CAR T cells. As the surviving BB.z CD5 CAR T cells retained the desired central memory phenotype, we aimed to circumvent the 4-1BB-mediated toxicity using a regulated expression system that reversibly inhibits CAR expression. This system minimized CAR signaling and T-cell fratricide during in vitro expansion in the presence of a small-molecule inhibitor, and restored CAR expression and antitumor function of transduced T cells in vivo These studies reveal a mechanism by which 4-1BB costimulation impairs expansion of CD5 CAR T cells and offer a solution to mitigate this toxicity. Cancer Immunol Res; 6(1); 47-58. ©2017 AACR.

Tonic 4-1BB Costimulation in Chimeric Antigen Receptors Impedes T Cell Survival and Is Vector-Dependent

Antigen-independent tonic signaling by chimeric antigen receptors (CARs) can increase differentiation and exhaustion of T cells, limiting their potency. Incorporating 4-1BB costimulation in CARs may enable T cells to resist this functional exhaustion; however, the potential ramifications of tonic 4-1BB signaling in CAR T cells remain unclear. Here, we found that tonic CAR-derived 4-1BB signaling can produce toxicity in T cells via continuous TRAF2-dependent activation of the nuclear factor κB (NF-κB) pathway and augmented FAS-dependent cell death. This mechanism was amplified in a non-self-inactivating gammaretroviral vector through positive feedback on the long terminal repeat (LTR) promoter, further enhancing CAR expression and tonic signaling. Attenuating CAR expression by substitution with a self-inactivating lentiviral vector minimized tonic signaling and improved T cell expansion and anti-tumor function. These studies illuminate the interaction between tonic CAR signaling and the chosen expression platform and identify inhibitory properties of the 4-1BB costimulatory domain that have direct implications for rational CAR design.

A novel intracellular pool of LFA-1 is critical for asymmetric CD8+ T cell activation and differentiation

The integrin lymphocyte function-associated antigen 1 (LFA-1; CD11a/CD18) is a key T cell adhesion receptor that mediates stable interactions with antigen-presenting cell (APC), as well as chemokine-mediated migration. Using our newly generated CD11a-mYFP knock-in mice, we discovered that naive CD8⁺ T cells reserve a significant intracellular pool of LFA-1 in the uropod during migration. Intracellular LFA-1 quickly translocated to the cell surface with antigenic stimulus. Importantly, the redistribution of intracellular LFA-1 at the contact with APC was maintained during cell division and led to an unequal inheritance of LFA-1 in divided T cells. The daughter CD8⁺ T cells with disparate LFA-1 expression showed different patterns of migration on ICAM-1, APC interactions, and tissue retention, as well as altered effector functions. In addition, we identified Rab27 as an important regulator of the intracellular LFA-1 translocation. Collectively, our data demonstrate that an intracellular pool of LFA-1 in naive CD8⁺ T cells plays a key role in T cell activation and differentiation.

Association of Ribonuclease T2 Gene Polymorphisms With Decreased Expression and Clinical Characteristics of Severity in Crohn's Disease

BACKGROUND & AIMS

Variants in the tumor necrosis factor superfamily member 15 gene (TNFSF15, also called TL1A) have been associated with risk for inflammatory bowel disease (IBD). TL1A affects expression of multiple cytokines to promote mucosal inflammation. Little is known about the TL1A-response pathways that regulate cytokine expression. We investigated T-cell gene expression patterns to determine the mechanisms by which TL1A regulates cytokine production, and whether these associate with outcomes of patients with Crohn's disease (CD).

METHODS

Peripheral T cells isolated from normal donors were cultured with TL1A. We performed gene expression profile analysis by RNA sequencing of subsets of interferon gamma (IFNG)-producing and non-producing cells purified by flow cytometry. Unsupervised hierarchical clustering analysis was used to identify gene expression differences between these subsets. Ribonuclease T2 gene (RNASET2) expression and methylation were assessed by quantitative trait loci analyses. Clinical characteristics of patients (complications, resistance to therapy, and recurrence time) were associated with single nucleotide polymorphisms in RNASET2. We performed motif screening to identify polymorphisms that disrupt transcription factor binding sites. Levels of RNASET2 were knocked down with small interfering RNA in CD4+ T cells and the effect on protein expression was determined by proteomic analysis and cytokine production. Cell aggregation was measured by flow cytometry.

RESULTS

We identified 764 genes with at least a 2-fold difference in TL1A-mediated expression between IFNG-secreting and non-secreting T cells (P < 1 × 10-5). Many of these genes were located near IBD susceptibility variants. RNASET2 was the only IBD risk-associated gene with >5-fold down-regulation in the IFNG-secreting subset. RNASET2 disease risk variants were associated with decreased expression in peripheral and mucosal tissues and DNA hypermethylation in CD patients requiring surgical intervention. RNASET2 disease risk variants were associated in CD patients with more complicated disease or resistance to therapy, defined in part by failed response to treatment, increased length of intestinal resection, shorter time to repeat surgery, and high Rutgeerts score (>2) in postoperative endoscopy. The RNASET2 variant rs2149092 was predicted to disrupt a consensus binding site for the transcription factor ETS within an enhancer region. Expression of RNASET2 correlated with expression of ETS. RNASET2 knockdown in T cells increased expression of IFNG and intercellular adhesion molecule 1 (ICAM1) and induced T-cell aggregation. A blocking antibody against (ILFA1), disrupting the lymphocyte function-associated antigen 1-intercellular adhesion molecule 1 interaction, reduced T-cell production of IFNG.

CONCLUSIONS

We identified decreased expression of RNASET2 as a component of TL1A-mediated increase in production of IFNG and as a potential biomarker for patients with severe CD. Further study of the role of RNASET2 in regulating mucosal inflammation may lead to development of novel therapeutic targets.

CTLA-4-mediated posttranslational modifications direct cytotoxic T-lymphocyte differentiation

The blockade of inhibitory receptors such as CTLA-4 (CD152) is being used as immune-checkpoint therapy, offering a powerful strategy to restore effective immune responses against tumors. To determine signal components that are induced under the control of CTLA-4 we analyzed activated murine CD8⁺ T cells by quantitative proteomics. Accurate mass spectrometry revealed that CTLA-4 engagement led to central changes in the phosphorylation of proteins involved in T-cell differentiation. Beside other targets, we discovered a CTLA-4-mediated induction of the translational inhibitor programmed cell death-4 (PDCD4) as a result of FoxO1 nuclear re-localization. PDCD4 further bound a distinct set of mRNAs including Glutaminase, which points out a critical role for CTLA-4 in CD8⁺ T-cell metabolism. Consequently, PDCD4-deficient cytotoxic T-lymphocytes (CTLs) expressed increased amounts of otherwise repressed effector molecules and ultimately led to superior control of tumor growth in vivo. These findings reveal a novel CTLA-4-mediated pathway to attenuate CTLs and indicate the importance of post-transcriptional mechanisms in the regulation of anti-tumor immune responses.

Substrate-bound CCL21 and ICAM1 combined with soluble IL-6 collectively augment the expansion of antigen-specific murine CD4+ T cells

Immune processes within the complex microenvironment of the lymph node involve multiple intercellular, cell-matrix, and paracrine interactions, resulting in the expansion of antigen-specific T cells. Inspired by the lymph node microenvironment, we aimed to develop an ex vivo "synthetic immune niche" (SIN), which could effectively stimulate the proliferation of antigen-activated CD4⁺ T cells. This engineered SIN consisted of surfaces coated with the chemokine C-C motif ligand 21 (CCL21) and with the intercellular adhesion molecule 1 (ICAM1), coupled with the soluble cytokine interleukin 6 (IL-6) added to the culture medium. When activated by ovalbumin-loaded dendritic cells, OT-II T cells growing on regular uncoated culture plates form nonadherent, dynamic clusters around the dendritic cells. We found that functionalization of the plate surface with CCL21 and ICAM1 and the addition of IL-6 to the medium dramatically increases T-cell proliferation and transforms the culture topology from that of suspended 3-dimensional cell clusters into a firm, substrate-attached monolayer of cells. Our findings demonstrate that the components of this SIN collectively modulate T-cell interactions and augment both the proliferation and survival of T cells in an antigen-specific manner, potentially serving as a powerful approach for expanding immunotherapeutic T cells.

A genome-wide CRISPR screen identifies a restricted set of HIV host dependency factors

Host proteins are essential for HIV entry and replication and can be important nonviral therapeutic targets. Large-scale RNA interference (RNAi)-based screens have identified nearly a thousand candidate host factors, but there is little agreement among studies and few factors have been validated. Here we demonstrate that a genome-wide CRISPR-based screen identifies host factors in a physiologically relevant cell system. We identify five factors, including the HIV co-receptors CD4 and CCR5, that are required for HIV infection yet are dispensable for cellular proliferation and viability. Tyrosylprotein sulfotransferase 2 (TPST2) and solute carrier family 35 member B2 (SLC35B2) function in a common pathway to sulfate CCR5 on extracellular tyrosine residues, facilitating CCR5 recognition by the HIV envelope. Activated leukocyte cell adhesion molecule (ALCAM) mediates cell aggregation, which is required for cell-to-cell HIV transmission. We validated these pathways in primary human CD4⁺ T cells through Cas9-mediated knockout and antibody blockade. Our findings indicate that HIV infection and replication rely on a limited set of host-dispensable genes and suggest that these pathways can be studied for therapeutic intervention.

Defects in CD4+ T cell LFA-1 integrin-dependent adhesion and proliferation protect Cd47-/- mice from EAE

CD47 is known to play an important role in CD4⁺ T cell homeostasis. We recently reported a reduction in mice deficient in the Cd47 gene (Cd47^-/-) CD4⁺ T cell adhesion and transendothelial migration (TEM) in vivo and in vitro as a result of impaired expression of high-affinity forms of LFA-1 and VLA-4 integrins. A prior study concluded that Cd47^-/- mice were resistant to experimental autoimmune encephalomyelitis (EAE) as a result of complete failure in CD4⁺ T cell activation after myelin oligodendrocyte glycoprotein peptide 35-55 aa (MOG_35-55) immunization. As the prior EAE study was published before our report, authors could not have accounted for defects in T cell integrin function as a mechanism to protect Cd47^-/- in EAE. Thus, we hypothesized that failure of T cell activation involved defects in LFA-1 and VLA-4 integrins. We confirmed that Cd47^-/- mice were resistant to MOG_35-55-induced EAE. Our data, however, supported a different mechanism that was not a result of failure of CD4⁺ T cell activation. Instead, we found that CD4⁺ T cells in MOG_35-55-immunized Cd47^-/- mice were activated, but clonal expansion contracted within 72 h after immunization. We used TCR crosslinking and mitogen activation in vitro to investigate the underlying mechanism. We found that naïve Cd47^-/- CD4⁺ T cells exhibited a premature block in proliferation and survival because of impaired activation of LFA-1, despite effective TCR-induced activation. These results identify CD47 as an important regulator of LFA-1 and VLA-4 integrin-adhesive functions in T cell proliferation, as well as recruitment, and clarify the roles played by CD47 in MOG_35-55-induced EAE.

Adhesion- and Degranulation-Promoting Adapter Protein Promotes CD8 T Cell Differentiation and Resident Memory Formation and Function during an Acute Infection

During acute infections, naive Ag-specific CD8 T cells are activated and differentiate into effector T cells, most of which undergo contraction after pathogen clearance. A small population of CD8 T cells persists as memory to protect against future infections. We investigated the role of adhesion- and degranulation-promoting adapter protein (ADAP) in promoting CD8 T cell responses to a systemic infection. Naive Ag-specific CD8 T cells lacking ADAP exhibited a modest expansion defect early after Listeria monocytogenes or vesicular stomatitis virus infection but comparable cytolytic function at the peak of response. However, reduced numbers of ADAP-deficient CD8 T cells were present in the spleen after the peak of the response. ADAP deficiency resulted in a greater frequency of CD127(+) CD8 memory precursors in secondary lymphoid organs during the contraction phase. Reduced numbers of ADAP-deficient killer cell lectin-like receptor G1(-) CD8 resident memory T (TRM) cell precursors were present in a variety of nonlymphoid tissues at the peak of the immune response, and consequently the total numbers of ADAP-deficient TRM cells were reduced at memory time points. TRM cells that did form in the absence of ADAP were defective in effector molecule expression. ADAP-deficient TRM cells exhibited impaired effector function after Ag rechallenge, correlating with defects in their ability to form T cell-APC conjugates. However, ADAP-deficient TRM cells responded to TGF-β signals and recruited circulating memory CD8 T cells. Thus, ADAP regulates CD8 T cell differentiation events following acute pathogen challenge that are critical for the formation and selected functions of TRM cells in nonlymphoid tissues.

Hypoxia and antitumor CD8+ T cells: An incompatible alliance?

T Lymphocytes face pathologically low O₂ tensions within the tumor bed at which they will have to function in order to impact on the malignancy. Recent studies highlighting the importance of O₂ and hypoxia-inducible factors for CD8⁺ T-cell function and fate must now be integrated into tumor immunology concepts if immunotherapies are to progress. Here, we discuss, reinterpret, and reconcile the many apparent contradictions in these data and we propose that O₂ is a master regulator of the CD8⁺ T-cell response. Certain T cell functions are enhanced, others suppressed, but on balance, hypoxia is globally detrimental to the antitumor response.

The Role of Lymphatic Niches in T Cell Differentiation

Long-term immunity to many viral and bacterial pathogens requires CD8(+) memory T cell development, and the induction of long-lasting CD8(+) memory T cells from a naïve, undifferentiated state is a major goal of vaccine design. Formation of the memory CD8(+) T cell compartment is highly dependent on the early activation cues received by naïve CD8(+) T cells during primary infection. This review aims to highlight the cellularity of various niches within the lymph node and emphasize recent evidence suggesting that distinct types of T cell activation and differentiation occur within different immune contexts in lymphoid organs.

Acquisition of cancer stem cell-like properties in non-small cell lung cancer with acquired resistance to afatinib

Afatinib is an irreversible epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI) that is known to be effective against the EGFR T790M variant, which accounts for half of the mechanisms of acquired resistance to reversible EGFR-TKIs. However, acquired resistance to afatinib was also observed in clinical use. Thus, elucidating and overcoming the mechanisms of resistance are important issues in the treatment of non-small cell lung cancer. In this study, we established various afatinib-resistant cell lines and investigated the resistance mechanisms. EGFR T790M mutations were not detected using direct sequencing in established resistant cells. Several afatinib-resistant cell lines displayed MET amplification, and these cells were sensitive to the combination of afatinib plus crizotinib. As a further investigation, a cell line that acquired resistance to afatinib plus crizotinib, HCC827-ACR, was established from one of the MET amplified-cell lines. Several afatinib-resistant cell lines including HCC827-ACR displayed epithelial-to-mesenchymal transition (EMT) features and epigenetic silencing of miR-200c, which is a suppresser of EMT. In addition, these cell lines also exhibited overexpression of ALDH1A1 and ABCB1, which are putative stem cell markers, and resistance to docetaxel. In conclusion, we established afatinib-resistant cells and found that MET amplification, EMT, and stem cell-like features are observed in cells with acquired resistance to EGFR-TKIs. This finding may provide clues to overcoming resistance to EGFR-TKIs.

Negative Regulation of Memory Phenotype CD8 T Cell Conversion by Adhesion and Degranulation-Promoting Adapter Protein

The maintenance of T cell repertoire diversity involves the entry of newly developed T cells, as well as the maintenance of memory T cells generated from previous infections. This balance depends on competition for a limited amount of homeostatic cytokines and interaction with self-peptide MHC class I. In the absence of prior infection, memory-like or memory phenotype (MP) CD8 T cells can arise from homeostatic cytokine exposure during neonatal lymphopenia. Aside from downstream cytokine signaling, little is known about the regulation of the conversion of naive CD8 T cells to MP CD8 T cells during acute lymphopenia. We have identified a novel negative regulatory role for adhesion and degranulation-promoting adapter protein (ADAP) in CD8 T cell function. We show that in the absence of ADAP, naive CD8 T cells exhibit a diminished response to stimulatory Ag, but an enhanced response to weak agonist-altered peptide ligands. ADAP-deficient mice exhibit more MP CD8 T cells that occur following thymic emigration and are largely T cell intrinsic. Naive ADAP-deficient CD8 T cells are hyperresponsive to lymphopenia in vivo and exhibit enhanced activation of STAT5 and homeostatic Ag-independent proliferation in response to IL-15. Our results indicate that ADAP dampens naive CD8 T cell responses to lymphopenia and IL-15, and they demonstrate a novel Ag-independent function for ADAP in the suppression of MP CD8 T cell generation.

Radial mobility and cytotoxic function of retroviral replicating vector transduced, non-adherent alloresponsive T lymphocytes

We report a novel adaptation of the Radial Monolayer Cell Migration assay, first reported to measure the radial migration of adherent tumor cells on extracellular matrix proteins, for measuring the motility of fluorescently-labeled, non-adherent human or murine effector immune cells. This technique employs a stainless steel manifold and 10-well Teflon slide to focally deposit non-adherent T cells into wells prepared with either confluent tumor cell monolayers or extracellular matrix proteins. Light and/or multi-channel fluorescence microscopy is used to track the movement and behavior of the effector cells over time. Fluorescent dyes and/or viral vectors that code for fluorescent transgenes are used to differentially label the cell types for imaging. This method is distinct from similar-type in vitro assays that track horizontal or vertical migration/invasion utilizing slide chambers, agar or transwell plates. The assay allows detailed imaging data to be collected with different cell types distinguished by specific fluorescent markers; even specific subpopulations of cells (i.e., transduced/nontransduced) can be monitored. Surface intensity fluorescence plots are generated using specific fluorescence channels that correspond to the migrating cell type. This allows for better visualization of the non-adherent immune cell mobility at specific times. It is possible to gather evidence of other effector cell functions, such as cytotoxicity or transfer of viral vectors from effector to target cells, as well. Thus, the method allows researchers to microscopically document cell-to-cell interactions of differentially-labeled, non-adherent with adherent cells of various types. Such information may be especially relevant in the assessment of biologically-manipulated or activated immune cell types, where visual proof of functionality is desired with tumor target cells before their use for cancer therapy.

Impact of melatonin receptor deletion on intracellular signaling in spleen cells of mice after polymicrobial sepsis

OBJECTIVE

Melatonin is known to influence immune functions and to ameliorate outcome after septic challenge but it is unknown whether this is mediated by melatonin receptor activation. This study aimed to elucidate molecular differences in spleen and ex vivo splenocytes of wild-type (WT) and melatonin receptor double knockout mice (KO) after polymicrobial sepsis.

SUBJECTS AND METHODS

C3H/HeN wild-type and MT1-/-/MT2-/- mice underwent sham operation or cecum ligation and incision (CLI) and remained anesthetized for 1 h. Splenocytes were isolated and treated in culture with physiological melatonin concentrations (1 nM).

RESULTS

Plasma TNFα levels were consistently high after 1 h of CLI. Basal circulating leukocyte numbers were slightly higher in KO animals. We detected transcriptional differences in splenocytes of the knockout strain concerning proinflammatory mediators. Expression levels of IL-1β, IL-2, CXCR2, L-Selectin, TNFα, CXCL2 and ICAM-1 were strongly increased in splenocytes of KO mice. Splenocytes of KO mice displayed reduced ERK and p38 as well as increased JNK phosphorylation. None of the analyzed factors were influenced by melatonin in the culture medium.

CONCLUSIONS

The results of this study indicate an increased proinflammatory status of mice deficient in both membrane-bound melatonin receptors reflected by altered activation of MAPK cascades and transcriptional activation of proinflammatory mediators.

Telmisartan exerts anti-tumor effects by activating peroxisome proliferator-activated receptor-γ in human lung adenocarcinoma A549 cells

Telmisartan, a member of the angiotensin II type 1 receptor blockers, is usually used for cardiovascular diseases. Recent studies have showed that telmisartan has the property of PPARγ activation. Meanwhile, PPARγ is essential for tumor proliferation, invasion and metastasis. In this work we explore whether telmisartan could exert anti-tumor effects through PPARγ activation in A549 cells. MTT and trypan blue exclusion assays were included to determine the survival rates and cell viabilities. RT-PCR and western blotting were used to analyze the expression of ICAM-1, MMP-9 and PPARγ. DNA binding activity of PPARγ was evaluated by EMSA. Our data showed that the survival rates and cell viabilities of A549 cells were all reduced by telmisartan in a time- and concentration-dependent manner. Meanwhile, our results also demonstrated that telmisartan dose-dependently inhibited the expression of ICAM-1 and MMP-9. Moreover, the cytotoxic and anti-proliferative effects, ICAM-1 and MMP-9 inhibitive properties of telmisartan were totally blunted by the PPARγ antagonist GW9662. Our findings also showed that the expression of PPARγ was up-regulated by telmisartan in a dose dependent manner. And, the EMSA results also figured out that DNA binding activity of PPARγ was dose-dependently increased by telmisartan. Additionally, our data also revealed that telmisartan-induced PPARγ activation was abrogated by GW9662. Taken together, our results indicated that telmisartan inhibited the expression of ICAM-1 and MMP-9 in A549 cells, very likely through the up-regulation of PPARγ synthesis.