Regulation of T-cell activation by the cytoskeleton

Reproducible single cell annotation of programs underlying T-cell subsets, activation states, and functions

T-cells recognize antigens and induce specialized gene expression programs (GEPs) enabling functions including proliferation, cytotoxicity, and cytokine production. Traditionally, different classes of helper T-cells express mutually exclusive responses - for example, Th1, Th2, and Th17 programs. However, new single-cell RNA sequencing (scRNA-Seq) experiments have revealed a continuum of T-cell states without discrete clusters corresponding to these subsets, implying the need for new analytical frameworks. Here, we advance the characterization of T-cells with T-CellAnnoTator (TCAT), a pipeline that simultaneously quantifies pre-defined GEPs capturing activation states and cellular subsets. From 1,700,000 T-cells from 700 individuals across 38 tissues and five diverse disease contexts, we discover 46 reproducible GEPs reflecting the known core functions of T-cells including proliferation, cytotoxicity, exhaustion, and T helper effector states. We experimentally characterize several novel activation programs and apply TCAT to describe T-cell activation and exhaustion in Covid-19 and cancer, providing insight into T-cell function in these diseases.

Motility and tumor infiltration are key aspects of invariant natural killer T cell anti-tumor function

Dysfunction of invariant natural killer T (iNKT) cells contributes to immune resistance of tumors. Most mechanistic studies focus on their static functional status before or after activation, not considering motility as an important characteristic for antigen scanning and thus anti-tumor capability. Here we show via intravital imaging, that impaired motility of iNKT cells and their exclusion from tumors both contribute to the diminished anti-tumor iNKT cell response. Mechanistically, CD1d, expressed on macrophages, interferes with tumor infiltration of iNKT cells and iNKT-DC interactions but does not influence their intratumoral motility. VCAM1, expressed by cancer cells, restricts iNKT cell motility and inhibits their antigen scanning and activation by DCs via reducing CDC42 expression. Blocking VCAM1-CD49d signaling improves motility and activation of intratumoral iNKT cells, and consequently augments their anti-tumor function. Interference with macrophage-iNKT cell interactions further enhances the anti-tumor capability of iNKT cells. Thus, our findings provide a direction to enhance the efficacy of iNKT cell-based immunotherapy via motility regulation.

Extracellular vesicles and microvilli in the immune synapse

T cell receptor (TCR) binding to cognate antigen on the plasma membrane of an antigen-presenting cell (APC) triggers the immune synapse (IS) formation. The IS constitutes a dedicated contact region between different cells that comprises a signaling platform where several cues evoked by TCR and accessory molecules are integrated, ultimately leading to an effective TCR signal transmission that guarantees intercellular message communication. This eventually leads to T lymphocyte activation and the efficient execution of different T lymphocyte effector tasks, including cytotoxicity and subsequent target cell death. Recent evidence demonstrates that the transmission of information between immune cells forming synapses is produced, to a significant extent, by the generation and secretion of distinct extracellular vesicles (EV) from both the effector T lymphocyte and the APC. These EV carry biologically active molecules that transfer cues among immune cells leading to a broad range of biological responses in the recipient cells. Included among these bioactive molecules are regulatory miRNAs, pro-apoptotic molecules implicated in target cell apoptosis, or molecules triggering cell activation. In this study we deal with the different EV classes detected at the IS, placing emphasis on the most recent findings on microvilli/lamellipodium-produced EV. The signals leading to polarized secretion of EV at the synaptic cleft will be discussed, showing that the IS architecture fulfills a fundamental task during this route.

PD-1 inhibits T cell actin remodeling at the immunological synapse independently of its signaling motifs

Engagement of the receptor programmed cell death molecule 1 (PD-1) by its ligands PD-L1 and PD-L2 inhibits T cell-mediated immune responses. Blocking such signaling provides the clinical effects of PD-1-targeted immunotherapy. Here, we investigated the mechanisms underlying PD-1-mediated inhibition. Because dynamic actin remodeling is crucial for T cell functions, we characterized the effects of PD-1 engagement on actin remodeling at the immunological synapse, the interface between a T cell and an antigen-presenting cell (APC) or target cell. We used microscopy to analyze the formation of immunological synapses between PD-1+ Jurkat cells or primary human CD8+ cytotoxic T cells and APCs that presented T cell-activating antibodies and were either positive or negative for PD-L1. PD-1 binding to PD-L1 inhibited T cell spreading induced by antibody-mediated activation, which was characterized by the absence of the F-actin-dense distal lamellipodial network at the immunological synapse and the Arp2/3 complex, which mediates branched actin formation. PD-1-induced inhibition of actin remodeling also prevented the characteristic deformation of T cells that contact APCs and the release of cytotoxic granules. We showed that the effects of PD-1 on actin remodeling did not require its tyrosine-based signaling motifs, which are thought to mediate the co-inhibitory effects of PD-1. Our study highlights a previously unappreciated mechanism of PD-1-mediated suppression of T cell activity, which depends on the regulation of actin cytoskeleton dynamics in a signaling motif-independent manner.

Mechanobiological Strategies to Augment Cancer Treatment

Cancer cells exhibit aberrant extracellular matrix mechanosensing due to the altered expression of mechanosensory cytoskeletal proteins. Such aberrant mechanosensing of the tumor microenvironment (TME) by cancer cells is associated with disease development and progression. In addition, recent studies show that such mechanosensing changes the mechanobiological properties of cells, and in turn cells become susceptible to mechanical perturbations. Due to an increasing understanding of cell biomechanics and cellular machinery, several approaches have emerged to target the mechanobiological properties of cancer cells and cancer-associated cells to inhibit cancer growth and progression. In this Perspective, we summarize the progress in developing mechano-based approaches to target cancer by interfering with the cellular mechanosensing machinery and overall TME.

Disturbing cytoskeleton by engineered nanomaterials for enhanced cancer therapeutics

Cytoskeleton plays a significant role in the shape change, migration, movement, adhesion, cytokinesis, and phagocytosis of tumor cells. In clinical practice, some anti-cancer drugs achieve cytoskeletal therapeutic effects by acting on different cytoskeletal protein components. However, in the absence of cell-specific targeting, unnecessary cytoskeletal recombination in organisms would be disastrous, which would also bring about severe side effects during anticancer process. Nanomedicine have been proven to be superior to some small molecule drugs in cancer treatment due to better stability and targeting, and lower side effects. Therefore, this review summarized the recent developments of various nanomaterials disturbing cytoskeleton for enhanced cancer therapeutics, including carbon, noble metals, metal oxides, black phosphorus, calcium, silicon, polymers, peptides, and metal-organic frameworks, etc. A comprehensive analysis of the characteristics of cytoskeleton therapy as well as the future prospects and challenges towards clinical application were also discussed. We aim to drive on this emerging topic through refreshing perspectives based on our own work and what we have also learnt from others. This review will help researchers quickly understand relevant cytoskeletal therapeutic information to further advance the development of cancer nanomedicine.

NFAT1 and NFκB regulates expression of the common γ-chain cytokine receptor in activated T cells

INTRODUCTION

Cytokines of the common γ chain (γc) family are critical for the development, differentiation, and survival of T lineage cells. Cytokines play key roles in immunodeficiencies, autoimmune diseases, allergies, and cancer. Although γc is considered an assistant receptor to transmit cytokine signals and is an indispensable receptor in the immune system, its regulatory mechanism is not yet well understood.

OBJECTIVE

This study focused on the molecular mechanisms that γc expression in T cells is regulated under T cell receptor (TCR) stimulation.

METHODS

The γc expression in TCR-stimulated T cells was determined by flow cytometry, western blot and quantitative RT-PCR. The regulatory mechanism of γc expression in activated T cells was examined by promoter-luciferase assay and chromatin immunoprecipitation assays. NFAT1 and NFκB deficient cells generated using CRISPR-Cas9 and specific inhibitors were used to examine their role in regulation of γc expression. Specific binding motif was confirmed by γc promotor mutant cells generated using CRISPR-Cas9. IL-7TgγcTg mice were used to examine regulatory role of γc in cytokine signaling.

RESULTS

We found that activated T cells significantly upregulated γc expression, wherein NFAT1 and NFκB were key in transcriptional upregulation via T cell receptor stimulation. Also, we identified the functional binding site of the γc promoter and the synergistic effect of NFAT1 and NFκB in the regulation of γc expression. Increased γc expression inhibited IL-7 signaling and rescued lymphoproliferative disorder in an IL-7Tg animal model, providing novel insights into T cell homeostasis.

CONCLUSION

Our results indicate functional cooperation between NFAT1 and NFκB in upregulating γc expression in activated T cells. As γc expression also regulates γc cytokine responsiveness, our study suggests that γc expression should be considered as one of the regulators in γc cytokine signaling and the development of T cell immunotherapies. Video Abstract.

Loss of the KN Motif and AnKyrin Repeat Domain 1 (KANK1) Leads to Lymphoid Compartment Dysregulation in Murine Model

The KN Motif and AnKyrin Repeat Domain 1 (KANK1) is proposed as a tumour suppressor gene, as its expression is reduced or absent in several types of tumour tissue, and over-expressing the protein inhibited the proliferation of tumour cells in solid cancer models. We report a novel germline loss of heterozygosity mutation encompassing the KANK1 gene in a young patient diagnosed with myelodysplastic neoplasm (MDS) with no additional disease-related genomic aberrations. To study the potential role of KANK1 in haematopoiesis, we generated a new transgenic mouse model with a confirmed loss of KANK1 expression. KANK1 knockout mice did not develop any haematological abnormalities; however, the loss of its expression led to alteration in the colony forming and proliferative potential of bone marrow (BM) cells and a decrease in hematopoietic stem and progenitor cells (HSPCs) population frequency. A comprehensive marker expression analysis of lineage cell populations indicated a role for Kank1 in lymphoid cell development, and total protein analysis suggests the involvement of Kank1 in BM cells' cytoskeleton formation and mobility.

LFA-1 knockout inhibited the tumor growth and is correlated with treg cells

Cancer immunotherapy has been proven to be clinically effective in multiple types of cancers. Lymphocyte function-associated antigen 1 (LFA-1), a member of the integrin family of adhesion molecules, is expressed mainly on αβ T cells. LFA-1 is associated with tumor immune responses, but its exact mechanism remains unknown. Here, two kinds of mice tumor model of LFA-1 knockout (LFA-1-/-) mice bearing subcutaneous tumor and Apc Min/+;LFA-1-/- mice were used to confirm that LFA-1 knockout resulted in inhibition of tumor growth. Furthermore, it also demonstrated that the numbers of regulatory T cells (Treg cells) in the spleen, blood, mesenteric lymph nodes were decreased in LFA-1-/- mice, and the numbers of Treg cells in mesenteric lymph nodes were also decreased in Apc Min/+;LFA-1-/- mice compared with Apc Min/+ mice. LFA-1 inhibitor (BIRT377) was administered to subcutaneous tumor-bearing LFA-1+/+ mice, and the results showed that the tumor growth was inhibited and the number of Treg cells was reduced. The analysis of TIMER tumor database indicated that LFA-1 expression is positively associated with Treg cells and TNM stage. Conclusively, this suggests that LFA-1 knockout would inhibit tumor growth and is correlated with Treg cells. LFA-1 may be one potential target for cancer immunotherapy. Video Abstract.

A regulatory circuit controlled by extranuclear and nuclear retinoic acid receptor α determines T cell activation and function

Ligation of retinoic acid receptor alpha (RARα) by RA promotes varied transcriptional programs associated with immune activation and tolerance, but genetic deletion approaches suggest the impact of RARα on TCR signaling. Here, we examined whether RARα would exert roles beyond transcriptional regulation. Specific deletion of the nuclear isoform of RARα revealed an RARα isoform in the cytoplasm of T cells. Extranuclear RARα was rapidly phosphorylated upon TCR stimulation and recruited to the TCR signalosome. RA interfered with extranuclear RARα signaling, causing suboptimal TCR activation while enhancing FOXP3+ regulatory T cell conversion. TCR activation induced the expression of CRABP2, which translocates RA to the nucleus. Deletion of Crabp2 led to increased RA in the cytoplasm and interfered with signalosome-RARα, resulting in impaired anti-pathogen immunity and suppressed autoimmune disease. Our findings underscore the significance of subcellular RA/RARα signaling in T cells and identify extranuclear RARα as a component of the TCR signalosome and a determinant of immune responses.

TMEM123 a key player in immune surveillance of colorectal cancer

Colorectal cancer (CRC) is a leading cause of cancer-associated death. In the tumor site, the interplay between effector immune cells and cancer cells determines the balance between tumor elimination or outgrowth. We discovered that the protein TMEM123 is over-expressed in tumour-infiltrating CD4 and CD8 T lymphocytes and it contributes to their effector phenotype. The presence of infiltrating TMEM123+ CD8+ T cells is associated with better overall and metastasis-free survival. TMEM123 localizes in the protrusions of infiltrating T cells, it contributes to lymphocyte migration and cytoskeleton organization. TMEM123 silencing modulates the underlying signaling pathways dependent on the cytoskeletal regulator WASP and the Arp2/3 actin nucleation complex, which are required for synaptic force exertion. Using tumoroid-lymphocyte co-culture assays, we found that lymphocytes form clusters through TMEM123, anchoring to cancer cells and contributing to their killing. We propose an active role for TMEM123 in the anti-cancer activity of T cells within tumour microenvironment.

Biophysical and mechanobiological considerations for T-cell-based immunotherapy

Immunotherapies modulate the body's defense system to treat cancer. While these therapies have shown efficacy against multiple types of cancer, patient response rates are limited, and the off-target effects can be severe. Typical approaches in developing immunotherapies tend to focus on antigen targeting and molecular signaling, while overlooking biophysical and mechanobiological effects. Immune cells and tumor cells are both responsive to biophysical cues, which are prominent in the tumor microenvironment. Recent studies have shown that mechanosensing - including through Piezo1, adhesions, and Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) - influences tumor-immune interactions and immunotherapeutic efficacy. Furthermore, biophysical methods such as fluidic systems and mechanoactivation schemes can improve the controllability and manufacturing of engineered T cells, with potential for increasing therapeutic efficacy and specificity. This review focuses on leveraging advances in immune biophysics and mechanobiology toward improving chimeric antigen receptor (CAR) T-cell and anti-programmed cell death protein 1 (anti-PD-1) therapies.

A Proteomic Analysis of Detergent-Resistant Membranes in HIV Virological Synapse: The Involvement of Vimentin in CD4 Polarization

The cell-cell contact between HIV-1-infected and uninfected cells forms a virological synapse (VS) to allow for efficient HIV-1 transmission. Not only are HIV-1 components polarized and accumulate at cell-cell interfaces, but viral receptors and lipid raft markers are also. To better understand the nature of the HIV-1 VS, detergent-resistant membrane (DRM) fractions were isolated from an infected-uninfected cell coculture and compared to those from non-coculture samples using 2D fluorescence difference gel electrophoresis. Mass spectrometry revealed that ATP-related enzymes (ATP synthase subunit and vacuolar-type proton ATPase), protein translation factors (eukaryotic initiation factor 4A and mitochondrial elongation factor Tu), protein quality-control-related factors (protein disulfide isomerase A3 and 26S protease regulatory subunit), charged multivesicular body protein 4B, and vimentin were recruited to the VS. Membrane flotation centrifugation of the DRM fractions and confocal microscopy confirmed these findings. We further explored how vimentin contributes to the HIV-1 VS and found that vimentin supports HIV-1 transmission through the recruitment of CD4 to the cell-cell interface. Since many of the molecules identified in this study have previously been suggested to be involved in HIV-1 infection, we suggest that a 2D difference gel analysis of DRM-associated proteins may reveal the molecules that play crucial roles in HIV-1 cell-cell transmission.

ARPC5 isoforms and their regulation by calcium-calmodulin-N-WASP drive distinct Arp2/3-dependent actin remodeling events in CD4 T cells

CD4 T cell activation induces nuclear and cytoplasmic actin polymerization via the Arp2/3 complex to activate cytokine expression and strengthen T cell receptor (TCR) signaling. Actin polymerization dynamics and filament morphology differ between nucleus and cytoplasm. However, it is unclear how the Arp2/3 complex mediates distinct nuclear and cytoplasmic actin polymerization in response to a common stimulus. In humans, the ARP3, ARPC1, and ARPC5 subunits of the Arp2/3 complex exist as two different isoforms, resulting in complexes with different properties. Here, we show that the Arp2/3 subunit isoforms ARPC5 and ARPC5L play a central role in coordinating distinct actin polymerization events in CD4 T cells. While ARPC5L is heterogeneously expressed in individual CD4 T cells, it specifically drives nuclear actin polymerization upon T cell activation. In contrast, ARPC5 is evenly expressed in CD4 T cell populations and is required for cytoplasmic actin dynamics. Interestingly, nuclear actin polymerization triggered by a different stimulus, DNA replication stress, specifically requires ARPC5 but not ARPC5L. TCR signaling but not DNA replication stress induces nuclear actin polymerization via nuclear calcium-calmodulin signaling and N-WASP. Diversity in the molecular properties and individual expression patterns of ARPC5 subunit isoforms thus tailors Arp2/3-mediated actin polymerization to different physiological stimuli.

Negative intracellular regulators of T-cell receptor (TCR) signaling as potential antitumor immunotherapy targets

Immunotherapy strategies aim to mobilize immune defenses against tumor cells by targeting mainly T cells. Co-inhibitory receptors or immune checkpoints (ICPs) (such as PD-1 and CTLA4) can limit T cell receptor (TCR) signal propagation in T cells. Antibody-based blocking of immune checkpoints (immune checkpoint inhibitors, ICIs) enable escape from ICP inhibition of TCR signaling. ICI therapies have significantly impacted the prognosis and survival of patients with cancer. However, many patients remain refractory to these treatments. Thus, alternative approaches for cancer immunotherapy are needed. In addition to membrane-associated inhibitory molecules, a growing number of intracellular molecules may also serve to downregulate signaling cascades triggered by TCR engagement. These molecules are known as intracellular immune checkpoints (iICPs). Blocking the expression or the activity of these intracellular negative signaling molecules is a novel field of action to boost T cell-mediated antitumor responses. This area is rapidly expanding. Indeed, more than 30 different potential iICPs have been identified. Over the past 5 years, several phase I/II clinical trials targeting iICPs in T cells have been registered. In this study, we summarize recent preclinical and clinical data demonstrating that immunotherapies targeting T cell iICPs can mediate regression of solid tumors including (membrane associated) immune-checkpoint inhibitor refractory cancers. Finally, we discuss how these iICPs are targeted and controlled. Thereby, iICP inhibition is a promising strategy opening new avenues for future cancer immunotherapy treatments.

Transcriptome profiling reveals transcriptional regulation of VISTA in T cell activation

PURPOSE

V-domain immunoglobulin suppressor of T-cell activation (VISTA) is a novel type of immune checkpoint. This study was performed to explore the potential mechanism by which different domains of VISTA affect T-cell activation and search for potential interacting proteins.

METHODS

Stably transfected Jurkat cell lines were constructed to overexpress human VISTA (VISTA-FL), cytoplasmic domain deletion mutants (VISTA-ΔECD) and extracellular domain deletion mutants (VISTA- ΔCD). Empty vector (EV) control cell lines were constructed. Four stable cell lines were subjected to transcriptome sequencing after stimulation with PMA and PHA. The differentially expressed genes (DEGs) were analysed to explore the potential pathway by which VISTA inhibits T-cell activation. Proteinprotein interaction (PPI) network analysis was used to search for potential interacting proteins of VISTA.

RESULTS

In this study, 1256 DEGs were identified in Jurkat-VISTA-FL cells, 740 DEGs in Jurkat-VISTA-ΔCD cells, and 5605 DEGs in Jurkat-VISTA-ΔECD cells compared with Jurkat-EV cells. DEGs were mainly enriched in pathways related to T-cell differentiation, T-cell receptor signalling pathway and T-cell migration in Jurkat-VISTA-ΔECD cells; with cholesterol biosynthesis in Jurkat-VISTA-ΔCD cells; and with the inflammatory response in Jurkat-VISTA-FL cells. HHLA2 and CTH were identified as potential partners that interact directly with VISTA. The results also show an indirect interaction between VISTA and PSGL-1.

CONCLUSIONS

This study revealed the pathways by which VISTA is involved in T-cell activation and identified the potential binding partners of VISTA through RNA-seq, providing valuable resources for developing in-depth studies of the action mechanisms of VISTA as a potential target for cancer and inflammatory diseases.

Mechano-modulation of T cells for cancer immunotherapy

Immunotherapy, despite its promise for future anti-cancer approach, faces significant challenges, such as off-tumor side effects, innate or acquired resistance, and limited infiltration of immune cells into stiffened extracellular matrix (ECM). Recent studies have highlighted the importance of mechano-modulation/-activation of immune cells (mainly T cells) for effective caner immunotherapy. Immune cells are highly sensitive to the applied physical forces and matrix mechanics, and reciprocally shape the tumor microenvironment. Engineering T cells with tuned properties of materials (e.g., chemistry, topography, and stiffness) can improve their expansion and activation ex vivo, and their ability to mechano-sensing the tumor specific ECM in vivo where they perform cytotoxic effects. T cells can also be exploited to secrete enzymes that soften ECM, thus increasing tumor infiltration and cellular therapies. Furthermore, T cells, such as chimeric antigen receptor (CAR)-T cells, genomic engineered to be spatiotemporally controllable by physical stimuli (e.g., ultrasound, heat, or light), can mitigate adverse off-tumor effects. In this review, we communicate these recent cutting-edge endeavors devoted to mechano-modulating/-activating T cells for effective cancer immunotherapy, and discuss future prospects and challenges in this field.

Deciphering actin remodelling in immune cells through the prism of actin-related inborn errors of immunity

Actin cytoskeleton remodelling drives cell motility, cell to cell contacts, as well as membrane and organelle dynamics. Those cellular activities operate at a particularly high pace in immune cells since these cells migrate through various tissues, interact with multiple cellular partners, ingest microorganisms and secrete effector molecules. The central and multifaceted role of actin cytoskeleton remodelling in sustaining immune cell tasks in humans is highlighted by rare inborn errors of immunity due to mutations in genes encoding proximal and distal actin regulators. In line with the specificity of some of the actin-based processes at work in immune cells, the expression of some of the affected genes, such as WAS, ARPC1B and HEM1 is restricted to the hematopoietic compartment. Exploration of these natural deficiencies highlights the fact that the molecular control of actin remodelling is tuned distinctly in the various subsets of myeloid and lymphoid immune cells and sustains different networks associated with a vast array of specialized tasks. Furthermore, defects in individual actin remodelling proteins are usually associated with partial cellular impairments highlighting the plasticity of actin cytoskeleton remodelling. This review covers the roles of disease-associated actin regulators in promoting the actin-based processes of immune cells. It focuses on the specific molecular function of those regulators across various immune cell subsets and in response to different stimuli. Given the fact that numerous immune-related actin defects have only been characterized recently, we further discuss the challenges lying ahead to decipher the underlying patho-mechanisms.

Analysis of centrosomal area actin reorganization and centrosome polarization upon lymphocyte activation at the immunological synapse

T cell receptor (TCR) and B cell receptor (BCR) stimulation of T and B lymphocytes, by antigen presented on an antigen-presenting cell (APC) induces the formation of the immunological synapse (IS). IS formation is associated with an initial increase in cortical filamentous actin (F-actin) at the IS, followed by a decrease in F-actin density at the central region of the IS, which contains the secretory domain. This is followed by the convergence of secretion vesicles towards the centrosome, and the polarization of the centrosome to the IS. These reversible, cortical actin cytoskeleton reorganization processes occur during lytic granule secretion in cytotoxic T lymphocytes (CTL) and natural killer (NK) cells, proteolytic granules secretion in B lymphocytes and during cytokine-containing vesicle secretion in T-helper (Th) lymphocytes. In addition, several findings obtained in T and B lymphocytes forming IS show that actin cytoskeleton reorganization also occurs at the centrosomal area. F-actin reduction at the centrosomal area appears to be associated with centrosome polarization. In this chapter we deal with the analysis of centrosomal area F-actin reorganization, as well as the centrosome polarization analysis toward the IS.

Coronavirus and the Cytoskeleton of Virus-Infected Cells

The cytoskeleton, which includes actin filaments, microtubules, and intermediate filaments, is one of the most important networks in the cell and undertakes many fundamental life activities. Among them, actin filaments are mainly responsible for maintaining cell shape and mediating cell movement, microtubules are in charge of coordinating all cargo transport within the cell, and intermediate filaments are mainly thought to guard against external mechanical pressure. In addition to this, cytoskeleton networks are also found to play an essential role in multiple viral infections. Due to the COVID-19 epidemic, including SARS-CoV-2, SARS-CoV and MERS-CoV, so many variants have caused wide public concern, that any virus infection can potentially bring great harm to human beings and society. Therefore, it is of great importance to study coronavirus infection and develop antiviral drugs and vaccines. In this chapter, we summarize in detail how the cytoskeleton responds and participates in coronavirus infection by analyzing the possibility of the cytoskeleton and its related proteins as antiviral targets, thereby providing ideas for finding more effective treatments.

Activation kinetics of regulatory molecules during immunological synapse in T cells

T cell activation through TCR stimulation leads to the formation of the immunological synapse (IS), a specialized adhesion organized between T lymphocytes and antigen presenting cells (APCs) in which a dynamic interaction among signaling molecules, the cytoskeleton and intracellular organelles achieves proper antigen-mediated stimulation and effector function. The kinetics of molecular reactions at the IS is essential to determine the quality of the response to the antigen stimulation. Herein, we describe methods based on biochemistry, flow cytometry and imaging in live and fixed cells to study the activation state and dynamics of regulatory molecules at the IS in the Jurkat T cell line CH7C17 and primary human and mouse CD4⁺ T lymphocytes stimulated by antigen presented by Raji and HOM2 B cell lines and human and mouse dendritic cells.

The T Cell Journey: A Tour de Force

T cells act as the puppeteers in the adaptive immune response, and their dysfunction leads to the initiation and progression of pathological conditions. During their lifetime, T cells experience myriad forces that modulate their effector functions. These forces are imposed by interacting cells, surrounding tissues, and shear forces from fluid movement. In this review, a journey with T cells is made, from their development to their unique characteristics, including the early studies that uncovered their mechanosensitivity. Then the studies pertaining to the responses of T cell activation to changes in antigen-presenting cells' physical properties, to their immediate surrounding extracellular matrix microenvironment, and flow conditions are highlighted. In addition, it is explored how pathological conditions like the tumor microenvironment can hinder T cells and allow cancer cells to escape elimination.

Lack of Nck1 protein and Nck-CD3 interaction caused the increment of lipid content in Jurkat T cells

Background

The non-catalytic region of tyrosine kinase (Nck) is an adaptor protein, which is ubiquitously expressed in many types of cells. In T cells, the Nck1 isoform promotes T cell receptor signalling as well as actin polymerisation. However, the role of Nck1 in the lipid metabolism in T cells is unknown. In the present study, we investigated the effect of the Nck1 protein and Nck–CD3 interaction on lipid metabolism and on the physical and biological properties of Jurkat T cells, using a newly developed holotomographic microscope.

Results

Holotomographic microscopy showed that Nck1-knocked-out cells had membrane blebs and were irregular in shape compared to the rounded control cells. The cell size and volume of Nck1-deficient cells were comparable to those of the control cells. Nck1-knocked-out Jurkat T cells had a greater lipid content, lipid mass/cell mass ratio, and lipid metabolite levels than the control cells. Interestingly, treatment with a small molecule, AX-024, which inhibited Nck–CD3 interaction, also caused an increase in the lipid content in wild-type Jurkat T cells, as found in Nck1-deficient cells.

Conclusions

Knockout of Nck1 protein and hindrance of the Nck–CD3 interaction cause the elevation of lipid content in Jurkat T cells.

The β-carboline Harmine improves the therapeutic benefit of anti-PD1 in melanoma by increasing the MHC-I-dependent antigen presentation

Harmine is a dual-specificity tyrosine-regulated kinase 1A (DYRK1A) inhibitor that displays a number of biological and pharmacological properties. Also referred to as ACB1801 molecule, we have previously reported that harmine increases the presentation of major histocompatibility complex (MHC)-I-dependent antigen on melanoma cells. Here, we show that ACB1801 upregulates the mRNA expression of several proteins of the MHC-I such as Transporter Associated with antigen Processing TAP1 and 2, Tapasin and Lmp2 (hereafter referred to as MHC-I signature) in melanoma cells. Treatment of mice bearing melanoma B16-F10 with ACB1801 inhibits the growth and weight of tumors and induces a profound modification of the tumor immune landscape. Strikingly, combining ACB1801 with anti-PD1 significantly improves its therapeutic benefit in B16-F10 melanoma-bearing mice. These results suggest that, by increasing the MHC-I, ACB1801 can be combined with anti-PD1/PD-L1 therapy to improve the survival benefit in cancer patients displaying a defect in MHC-I expression. This is further supported by data showing that i) high expression levels of TAP1, Tapasin and Lmp2 was observed in melanoma patients that respond to anti-PD1; ii) the survival is significantly improved in melanoma patients who express high MHC-I signature relative to those expressing low MHC-I signature; and iii) high expression of MHC-I signature in melanoma patients was correlated with increased expression of CD8 and NK cell markers and overexpression of proinflammatory chemokines involved in the recruitment of CD8+ T cells.

The Shape of Nanostructures Encodes Immunomodulation of Carbohydrate Antigen and Vaccine Development

Gold nanoparticles (AuNPs) have shown remarkable potential for vaccine development, but the influence of the size and shape of nanoparticles modulating the T-cell-dependent carbohydrate antigen processing and immunomodulation is poorly investigated. Here, we described how different shapes and sizes of gold nanostructures carrying adjuvant modulate carbohydrate-based antigen processing in murine dendritic cells (mDCs) and subsequent T-cell activation produce a robust antibody response. As a prototype, CpG-adjuvant-coated spherical and rod- and star-shaped AuNPs were conjugated to the tripodal Tn-glycopeptide antigen to study their DC uptake and activation of T-cells in a DCs/T-cell co-culture assay. Our results showed that the spherical and star-shaped AuNPs displayed relatively weak receptor-mediated uptake and endosomal sequestration; however, they induced a high level of T helper-1 (Th1) biasing immune responses compared with rod-shaped AuNPs. Furthermore, the in vivo administration of AuNPs showed that the small spherical and star-shaped AuNPs induced an effective anti-Tn-glycopeptide immunoglobulin (IgG) antibody response compared with rod-shaped AuNPs. These results indicated that one could obtain superior carbohydrate vaccines by varying the shape and size parameters of nanostructures.

LPA suppresses T cell function by altering the cytoskeleton and disrupting immune synapse formation

Cancer and chronic infections often increase levels of the bioactive lipid, lysophosphatidic acid (LPA), that we have demonstrated acts as an inhibitory ligand upon binding LPAR5 on CD8 T cells, suppressing cytotoxic activity and tumor control. This study, using human and mouse primary T lymphocytes, reveals how LPA disrupts antigen-specific CD8 T cell:target cell immune synapse (IS) formation and T cell function via competing for cytoskeletal regulation. Specifically, we find upon antigen-specific T cell:target cell formation, IP3R1 localizes to the IS by a process dependent on mDia1 and actin and microtubule polymerization. LPA not only inhibited IP3R1 from reaching the IS but also altered T cell receptor (TCR)–induced localization of RhoA and mDia1 impairing F-actin accumulation and altering the tubulin code. Consequently, LPA impeded calcium store release and IS-directed cytokine secretion. Thus, targeting LPA signaling in chronic inflammatory conditions may rescue T cell function and promote antiviral and antitumor immunity.

The Actin Regulators Involved in the Function and Related Diseases of Lymphocytes

Actin is an important cytoskeletal protein involved in signal transduction, cell structure and motility. Actin regulators include actin-monomer-binding proteins, Wiskott-Aldrich syndrome (WAS) family of proteins, nucleation proteins, actin filament polymerases and severing proteins. This group of proteins regulate the dynamic changes in actin assembly/disassembly, thus playing an important role in cell motility, intracellular transport, cell division and other basic cellular activities. Lymphocytes are important components of the human immune system, consisting of T-lymphocytes (T cells), B-lymphocytes (B cells) and natural killer cells (NK cells). Lymphocytes are indispensable for both innate and adaptive immunity and cannot function normally without various actin regulators. In this review, we first briefly introduce the structure and fundamental functions of a variety of well-known and newly discovered actin regulators, then we highlight the role of actin regulators in T cell, B cell and NK cell, and finally provide a landscape of various diseases associated with them. This review provides new directions in exploring actin regulators and promotes more precise and effective treatments for related diseases.

T Lymphocyte and CAR-T Cell-Derived Extracellular Vesicles and Their Applications in Cancer Therapy

Extracellular vesicles (EV) are a very diverse group of cell-derived vesicles released by almost all kind of living cells. EV are involved in intercellular exchange, both nearby and systemically, since they induce signals and transmit their cargo (proteins, lipids, miRNAs) to other cells, which subsequently trigger a wide variety of biological responses in the target cells. However, cell surface receptor-induced EV release is limited to cells from the immune system, including T lymphocytes. T cell receptor activation of T lymphocytes induces secretion of EV containing T cell receptors for antigen and several bioactive molecules, including proapoptotic proteins. These EV are specific for antigen-bearing cells, which make them ideal candidates for a cell-free, EV-dependent cancer therapy. In this review we examine the generation of EV by T lymphocytes and CAR-T cells and some potential therapeutic approaches of these EV.

Case report: Primary immunodeficiency due to a novel mutation in CARMIL2 and its response to combined immunomodulatory therapy

Capping protein regulator and myosin 1 linker 2 (CARMIL2) is necessary for invadopodia formation, cell polarity, lamellipodial assembly, membrane ruffling, acropinocytosis, and collective cell migration. CARMIL2 deficiency is a rare autosomal recessive disease characterized by dysfunction in naïve T-cell activation, proliferation, differentiation, and effector function and insufficient responses in T-cell memory. In this paper, we report a 9-year-old female patient with a novel pathogenic variant in CARMIL2 (c.2063C > G:p.Thr688Arg) who presented with various symptoms of primary immunodeficiencies including recurrent upper and lower respiratory infections, perioral and perineum papules, reddish impetiginized atopic dermatitis, oral ulcer, painful urination and vaginitis, otitis media, and failure to thrive. A missense mutation leading to insufficient CARMIL2 protein expression, reduced absolute T-cell and natural killer cell (NK cell) counts, and marked skewing to the naïve T-cell form was identified and indicated defective maturation of T cells and B cells. Following 1 year of multitargeted treatment with corticosteroids, hydroxychloroquine, mycophenolate mofetil, and thymosin, the patient presented with significant regression in rashes. CD4+ T-cell, CD8+ T-cell, and NK cell counts were significantly improved.

The role of protease-activated receptor 1 signaling in CD8 T cell effector functions

CD8 T cells are essential for adaptive immunity against viral infections. Protease activated receptor 1 (PAR1) is expressed by CD8 T cells; however, its role in T cell effector function is not well defined. Here we show that in human CD8 T cells, PAR1 stimulation accelerates calcium mobilization. Furthermore, PAR1 is involved in cytotoxic T cell function by facilitating granule trafficking via actin polymerization and repositioning of the microtubule organizing center (MTOC) toward the immunological synapse. In vivo, PAR1^−/− mice have reduced cytokine-producing T cells in response to a lymphocytic choriomeningitis virus (LCMV) infection and fail to efficiently control the virus. Specific deletion of PAR1 in LCMV GP33-specific CD8 T cells results in reduced expansion and diminished effector function. These data demonstrate that PAR1 plays a role in T cell activation and function, and this pathway could represent a new therapeutic strategy to modulate CD8 T cell effector function.

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PAR1 signaling in human CD8 T cells accelerates TCR-induced calcium mobilization

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PAR1 participates in the repositioning of the MTOC at the immunological synapse

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PAR1 facilitates polarized secretion of cytotoxic granules at the immunological synapse

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PAR1^−/− Gp33-specific CD8 T cells show reduced expansion and effector function

Modulation of Adaptive Immunity and Viral Infections by Ion Channels

Most cellular functions require of ion homeostasis and ion movement. Among others, ion channels play a crucial role in controlling the homeostasis of anions and cations concentration between the extracellular and intracellular compartments. Calcium (Ca2+) is one of the most relevant ions involved in regulating critical functions of immune cells, allowing the appropriate development of immune cell responses against pathogens and tumor cells. Due to the importance of Ca2+ in inducing the immune response, some viruses have evolved mechanisms to modulate intracellular Ca2+ concentrations and the mobilization of this cation through Ca2+ channels to increase their infectivity and to evade the immune system using different mechanisms. For instance, some viral infections require the influx of Ca2+ through ionic channels as a first step to enter the cell, as well as their replication and budding. Moreover, through the expression of viral proteins on the surface of infected cells, Ca2+ channels function can be altered, enhancing the pathogen evasion of the adaptive immune response. In this article, we review those ion channels and ion transporters that are essential for the function of immune cells. Specifically, cation channels and Ca2+ channels in the context of viral infections and their contribution to the modulation of adaptive immune responses.

Transmigration across a Steady-State Blood-Brain Barrie Induces Activation of Circulating Dendritic Cells Partly Mediated by Actin Cytoskeletal Reorganization

The central nervous system (CNS) is considered to be an immunologically unique site, in large part given its extensive protection by the blood–brain barrier (BBB). As our knowledge of the complex interaction between the peripheral immune system and the CNS expands, the mechanisms of immune privilege are being refined. Here, we studied the interaction of dendritic cells (DCs) with the BBB in steady–state conditions and observed that transmigrated DCs display an activated phenotype and stronger T cell-stimulatory capacity as compared to non-migrating DCs. Next, we aimed to gain further insights in the processes underlying activation of DCs following transmigration across the BBB. We investigated the interaction of DCs with endothelial cells as well as the involvement of actin cytoskeletal reorganization. Whereas we were not able to demonstrate that DCs engulf membrane fragments from fluorescently labelled endothelial cells during transmigration across the BBB, we found that blocking actin restructuring of DCs by latrunculin-A significantly impaired in vitro migration of DC across the BBB and subsequent T cell-stimulatory capacity, albeit no effect on migration-induced phenotypic activation could be demonstrated. These observations contribute to the current understanding of the interaction between DCs and the BBB, ultimately leading to the design of targeted therapies capable to inhibit autoimmune inflammation of the CNS.

Super-Resolution Imaging Approaches for Quantifying F-Actin in Immune Cells

Immune cells comprise a diverse set of cells that undergo a complex array of biological processes that must be tightly regulated. A key component of cellular machinery that achieves this is the cytoskeleton. Therefore, imaging and quantitatively describing the architecture and dynamics of the cytoskeleton is an important research goal. Optical microscopy is well suited to this task. Here, we review the latest in the state-of-the-art methodology for labeling the cytoskeleton, fluorescence microscopy hardware suitable for such imaging and quantitative statistical analysis software applicable to describing cytoskeletal structures. We also highlight ongoing challenges and areas for future development.

Targeting the Microtubule-Network Rescues CTL Killing Efficiency in Dense 3D Matrices

Efficacy of cytotoxic T lymphocyte (CTL)-based immunotherapy is still unsatisfactory against solid tumors, which are frequently characterized by condensed extracellular matrix. Here, using a unique 3D killing assay, we identify that the killing efficiency of primary human CTLs is substantially impaired in dense collagen matrices. Although the expression of cytotoxic proteins in CTLs remained intact in dense collagen, CTL motility was largely compromised. Using light-sheet microscopy, we found that persistence and velocity of CTL migration was influenced by the stiffness and porosity of the 3D matrix. Notably, 3D CTL velocity was strongly correlated with their nuclear deformability, which was enhanced by disruption of the microtubule network especially in dense matrices. Concomitantly, CTL migration, search efficiency, and killing efficiency in dense collagen were significantly increased in microtubule-perturbed CTLs. In addition, the chemotherapeutically used microtubule inhibitor vinblastine drastically enhanced CTL killing efficiency in dense collagen. Together, our findings suggest targeting the microtubule network as a promising strategy to enhance efficacy of CTL-based immunotherapy against solid tumors, especially stiff solid tumors.

Lattice Light-Sheet Microscopy Multi-dimensional Analyses (LaMDA) of T-Cell Receptor Dynamics Predict T-Cell Signaling States

Lattice light-sheet microscopy provides large amounts of high-dimensional, high-spatiotemporal resolution imaging data of cell surface receptors across the 3D surface of live cells, but user-friendly analysis pipelines are lacking. Here, we introduce lattice light-sheet microscopy multi-dimensional analyses (LaMDA), an end-to-end pipeline comprised of publicly available software packages that combines machine learning, dimensionality reduction, and diffusion maps to analyze surface receptor dynamics and classify cellular signaling states without the need for complex biochemical measurements or other prior information. We use LaMDA to analyze images of T-cell receptor (TCR) microclusters on the surface of live primary T cells under resting and stimulated conditions. We observe global spatial and temporal changes of TCRs across the 3D cell surface, accurately differentiate stimulated cells from unstimulated cells, precisely predict attenuated T-cell signaling after CD4 and CD28 receptor blockades, and reliably discriminate between structurally similar TCR ligands. All instructions needed to implement LaMDA are included in this paper.

T Cell Defects and Immunotherapy in Chronic Lymphocytic Leukemia

In the past few years, independent studies have highlighted the relevance of the tumor microenvironment (TME) in cancer, revealing a great variety of TME-related predictive markers, as well as identifying novel therapeutic targets in the TME. Cancer immunotherapy targets different components of the immune system and the TME at large in order to reinforce effector mechanisms or relieve inhibitory and suppressive signaling. Currently, it constitutes a clinically validated treatment for many cancers, including chronic lymphocytic leukemia (CLL), an incurable malignancy of mature B lymphocytes with great dependency on microenvironmental signals. Although immunotherapy represents a promising therapeutic option with encouraging results in CLL, the dysfunctional T cell compartment remains a major obstacle in such approaches. In the scope of this review, we outline the current immunotherapeutic treatment options in CLL in the light of recent immunogenetic and functional evidence of T cell impairment. We also highlight possible approaches for overcoming T cell defects and invigorating potent anti-tumor immune responses that would enhance the efficacy of immunotherapy.

Actin Dynamics at the T Cell Synapse as Revealed by Immune-Related Actinopathies

The actin cytoskeleton is composed of dynamic filament networks that build adaptable local architectures to sustain nearly all cellular activities in response to a myriad of stimuli. Although the function of numerous players that tune actin remodeling is known, the coordinated molecular orchestration of the actin cytoskeleton to guide cellular decisions is still ill defined. T lymphocytes provide a prototypical example of how a complex program of actin cytoskeleton remodeling sustains the spatio-temporal control of key cellular activities, namely antigen scanning and sensing, as well as polarized delivery of effector molecules, via the immunological synapse. We here review the unique knowledge on actin dynamics at the T lymphocyte synapse gained through the study of primary immunodeficiences caused by mutations in genes encoding actin regulatory proteins. Beyond the specific roles of individual actin remodelers, we further develop the view that these operate in a coordinated manner and are an integral part of multiple signaling pathways in T lymphocytes.

Dynein self-organizes while translocating the centrosome in T-cells

T-cells massively restructure their internal architecture upon reaching an antigen-presenting cell (APC) to form the immunological synapse (IS), a cell-cell interface necessary for efficient elimination of the APC. This reorganization occurs through tight coordination of cytoskeletal processes: actin forms a peripheral ring, and dynein motors translocate the centrosome toward the IS. A recent study proposed that centrosome translocation involves a microtubule (MT) bundle that connects the centrosome perpendicularly to dynein at the synapse center: the "stalk." The synapse center, however, is actin-depleted, while actin was assumed to anchor dynein. We propose that dynein is attached to mobile membrane anchors, and investigate this model with computer simulations. We find that dynein organizes into a cluster in the synapse when translocating the centrosome, aligning MTs into a stalk. By implementing both a MT-capture-shrinkage and a MT-sliding mechanism, we explicitly demonstrate that this organization occurs in both systems. However, results obtained with MT-sliding dynein are more robust and display a stalk morphology consistent with our experimental data obtained with expansion microscopy. Thus, our simulations suggest that actin organization in T-cells during activation defines a specific geometry in which MT-sliding dynein can self-organize into a cluster and cause stalk formation.

Cytoskeleton Dynamics in Peripheral T Cell Lymphomas: An Intricate Network Sustaining Lymphomagenesis

Defects in cytoskeleton functions support tumorigenesis fostering an aberrant proliferation and promoting inappropriate migratory and invasive features. The link between cytoskeleton and tumor features has been extensively investigated in solid tumors. However, the emerging genetic and molecular landscape of peripheral T cell lymphomas (PTCL) has unveiled several alterations targeting structure and function of the cytoskeleton, highlighting its role in cell shape changes and the aberrant cell division of malignant T cells. In this review, we summarize the most recent evidence about the role of cytoskeleton in PTCLs development and progression. We also discuss how aberrant signaling pathways, like JAK/STAT3, NPM-ALK, RhoGTPase, and Aurora Kinase, can contribute to lymphomagenesis by modifying the structure and the signaling properties of cytoskeleton.

Small GTPases of the Ras superfamily and glycogen phosphorylase regulation in T cells

Small GTPases, together with their regulatory and effector molecules, are key intermediaries in the complex signalling pathways that control almost all cellular processes, working as molecular switches to transduce extracellular cues into cellular responses that drive vital functions, such as intracellular transport, biomolecule synthesis, gene activation and cell survival. How all of these networks are linked to metabolic pathways is a subject of intensive study. Because any response to cellular action requires some form of energy input, elucidating how cells coordinate the signals that lead to a tangible response involving metabolism is central to understand cellular activities. In this review, we summarize recent advances in our understanding of the molecular basis of the crosstalk between small GTPases of the Ras superfamily, specifically Rac1 and Ras/Rap1, and glycogen phosphorylase in T lymphocytes. Abbreviations: ADCY: adenylyl cyclase; ADCY6: adenylyl cyclase 6; BCR: B cell receptor; cAMP: 3',5'-cyclic adenosine monophosphate; CRIB: Cdc42/Rac binding domain; DLPFC: dysfunction of the dorsolateral prefrontal cortex; EGFR: epidermal growth factor receptor; Epac2: exchange protein directly activated by cAMP; GDP: guanodine-5'-diphosphate; GPCRs: G protein-coupled receptors; GTP: guanodin-5'-triphosphate; IL2: interleukin 2; IL2-R: interleukin 2 receptor; JAK: janus kinases; MAPK: mitogen-activated protein kinase; O-GlcNAc: O-glycosylation; PAK1: p21 activated kinase 1; PI3K: phosphatidylinositol 3-kinase; PK: phosphorylase kinase; PKA: cAMP-dependent protein kinase A; PKCθ: protein kinase Cθ; PLCγ: phospholipase Cγ; Src: proto-oncogene tyrosine-protein kinase c; STAT: signal transducer and activator of transcription proteins.

Role of Actin Cytoskeleton Reorganization in Polarized Secretory Traffic at the Immunological Synapse

T cell receptor (TCR) and B cell receptor (BCR) stimulation by antigen presented on an antigen-presenting cell (APC) induces the formation of the immune synapse (IS), the convergence of secretory vesicles from T and B lymphocytes toward the centrosome, and the polarization of the centrosome to the immune synapse. Immune synapse formation is associated with an initial increase in cortical F-actin at the synapse, followed by a decrease in F-actin density at the central region of the immune synapse, which contains the secretory domain. These reversible, actin cytoskeleton reorganization processes occur during lytic granule degranulation in cytotoxic T lymphocytes (CTL) and cytokine-containing vesicle secretion in T-helper (Th) lymphocytes. Recent evidences obtained in T and B lymphocytes forming synapses show that F-actin reorganization also occurs at the centrosomal area. F-actin reduction at the centrosomal area appears to be involved in centrosome polarization. In this review we deal with the biological significance of both cortical and centrosomal area F-actin reorganization and some of the derived biological consequences.

The DNA-helicase HELLS drives ALK- ALCL proliferation by the transcriptional control of a cytokinesis-related program

Deregulation of chromatin modifiers, including DNA helicases, is emerging as one of the mechanisms underlying the transformation of anaplastic lymphoma kinase negative (ALK^-) anaplastic large cell lymphoma (ALCL). We recently identified the DNA-helicase HELLS as central for proficient ALK^-ALCL proliferation and progression. Here we assessed in detail its function by performing RNA-sequencing profiling coupled with bioinformatic prediction to identify HELLS targets and transcriptional cooperators. We demonstrated that HELLS, together with the transcription factor YY1, contributes to an appropriate cytokinesis via the transcriptional regulation of genes involved in cleavage furrow regulation. Binding target promoters, HELLS primes YY1 recruitment and transcriptional activation of cytoskeleton genes including the small GTPases RhoA and RhoU and their effector kinase Pak2. Single or multiple knockdowns of these genes reveal that RhoA and RhoU mediate HELLS effects on cell proliferation and cell division of ALK^-ALCLs. Collectively, our work demonstrates the transcriptional role of HELLS in orchestrating a complex transcriptional program sustaining neoplastic features of ALK^-ALCL.

Triggering interferon signaling in T cells with avadomide sensitizes CLL to anti-PD-L1/PD-1 immunotherapy

Cancer treatment has been transformed by checkpoint blockade therapies, with the highest anti-tumor activity of anti-programmed death 1 (PD-1) antibody therapy seen in Hodgkin lymphoma. Disappointingly, response rates have been low in the non-Hodgkin lymphomas, with no activity seen in relapsed/refractory chronic lymphocytic leukemia (CLL) with PD-1 blockade. Thus, identifying more powerful combination therapy is required for these patients. Here, we preclinically demonstrate enhanced anti-CLL activity following combinational therapy with anti-PD-1 or anti-PD-1 ligand (PD-L1) and avadomide, a cereblon E3 ligase modulator (CELMoD). Avadomide induced type I and II interferon (IFN) signaling in patient T cells, triggering a feedforward cascade of reinvigorated T-cell responses. Immune modeling assays demonstrated that avadomide stimulated T-cell activation, chemokine expression, motility and lytic synapses with CLL cells, as well as IFN-inducible feedback inhibition through upregulation of PD-L1. Patient-derived xenograft tumors treated with avadomide were converted to CD8+ T cell-inflamed tumor microenvironments that responded to anti-PD-L1/PD-1-based combination therapy. Notably, clinical analyses showed increased PD-L1 expression on T cells, as well as intratumoral expression of chemokine signaling genes in B-cell malignancy patients receiving avadomide-based therapy. These data illustrate the importance of overcoming a low inflammatory T-cell state to successfully sensitize CLL to checkpoint blockade-based combination therapy.

The CAR T-Cell Mechanoimmunology at a Glance

Chimeric antigen receptor (CAR) T-cell transfer is a novel paradigm of adoptive T-cell immunotherapy. When coming into contact with a target cancer cell, CAR T-cell forms a nonclassical immunological synapse with the cancer cell and dynamically orchestrates multiple critical forces to commit cytotoxic immune function. Such an immunologic process involves a force transmission in the CAR and a spatiotemporal remodeling of cell cytoskeleton to facilitate CAR activation and CAR T-cell cytotoxic function. Yet, the detailed understanding of such mechanotransduction at the interface between the CAR T-cell and the target cell, as well as its molecular structure and signaling, remains less defined and is just beginning to emerge. This article summarizes the basic mechanisms and principles of CAR T-cell mechanoimmunology, and various lessons that can be comparatively learned from interrogation of mechanotransduction at the immunological synapse in normal cytotoxic T-cell. The recent development and future application of novel bioengineering tools for studying CAR T-cell mechanoimmunology is also discussed. It is believed that this progress report will shed light on the CAR T-cell mechanoimmunology and encourage future researches in revealing the less explored yet important mechanosensing and mechanotransductive mechanisms involved in CAR T-cell immuno-oncology.

Death associated protein kinase 2 suppresses T-B interactions and GC formation

Germinal center (GC) formation is a critical step during T-dependent humoral immune responses. We report Death Associated Protein Kinase 2, a serine/threonine kinase, is rapidly induced in T cells following activation and plays an inhibitory role in T cell-mediated help for the GC formation. Specifically, T cells deficient in Dapk2 have an increased ability to physically conjugate with antigen-presenting B cells and to promote GC formation. However, Dapk2 does not regulate T cell receptor signaling strength and does not influence cytokine-driven T-cell subset polarization. Instead, Dapk2 dampens mTORC1 activities by associating with Raptor. Silencing of Raptor rescues defects observed with the Dapk2 insufficiency. Our study thus identifies Dapk2 as a new kinase likely involved in negative regulation of contact-dependent help delivery to B cells and GC formation.