Requirement for Tec kinases Rlk and Itk in T cell receptor signaling and immunity

Purification and characterization of full-length monomeric TEC family kinase, ITK

An early step in the activation of T cells via the T cell antigen receptor is the phosphorylation and activation of phospholipase C-γ1 (PLC-γ1) by the TEC family tyrosine kinase, interleukin-2 (IL-2) inducible T cell kinase (ITK). PLC-γ1 activation occurs within a multi-protein complex comprised of the enzymes ITK, PLC-γ1, and VAV, and the adapter molecules, LAT, Gads, SLP-76, and NCK. Studies of ITK activation and the role of this heptameric complex in regulating ITK activation and function have not been possible due to the lack of success in the expression and purification of full-length, monomeric ITK protein. In this study, we have produced soluble full-length wild-type ITK protein by co-expressing an N-terminal solubility-tagged ITK construct with a kinase-specific co-chaperone CDC37 in an insect cell line. Although the majority of the purified ITK protein is oligomerized, there is a 13-fold increase in the yield of monomeric protein production compared to the last reported purification. Previous studies suggest that the ITK oligomerization is mediated by intermolecular interactions. We created several mutants to disrupt these self-associations. Expression of one of these, the C96E/T110I mutant, produced 20 times more monomer than the wild-type construct. The in vitro characterization of these protein constructs showed that the purified protein is stable and functional. This successful purification and in vitro characterization of full-length monomeric ITK protein will aid in understanding the mechanism by which ITK is recruited into the heptameric complex and is enabled to phosphorylate and activate PLC-γ1.

Hair regrowth in alopecia areata and re-pigmentation in vitiligo in response to treatment: Commonalities and differences

Both alopecia areata (AA) and vitiligo share common pathogenesis involving, interferon-γ (IFN-γ) and interleukin-15 (IL-15) signalling pathways that activate cytotoxic CD8+ T lymphocytes. These shared mechanisms may explain why both diseases respond to currently available treatments (e.g. topical/systemic corticosteroid) and emerging treatment modalities. As compared with the speed of re-pigmentation in vitiligo lesions, the regeneration of pigmented terminal hair follicles in AA lesions appears fast in response to treatments targeting the inhibition of the Janus kinases (JAKs) and other kinases. We summarize the commonalities and differences between AA and vitiligo focusing on the treatment modalities, followed by recent findings associated with hair follicle stem cells (HFSC) in hair bulge (HBg) and melanocyte stem cells (McSC) in HBg and hair germ (HGm). We then discuss how HFSC and HGm-McSC are involved in the initiation of anagen phase, followed by pigmented terminal hair regrowth in the recovering AA lesions in association with immunology. We also discuss how HBg-McSC contribute to the migration of fully dendritic mature melanocytes into interfollicular epidermis and the equal distribution of melanin in recovering vitiligo lesions. Finally, we present four hypotheses to elucidate the delayed distribution of melanin by mature melanocytes in depigmented vitiligo lesions from the aspects of stem cell biology, as compared with quick hair recovery in AA: (1) McSC are less abundant than HFSC. (2) McSC require a long travel, whereas HFSC reside close to hair regeneration trigger point. (3) Keratinocyte scaffold to accept melanin is not well preserved, whereas scaffold for hair regrowth is well preserved. (4) Inhibitors targeting JAKs and other kinases have less direct effects on melanocyte proliferation and differentiation in vitiligo than hair regrowth in AA. Our review provides an overview of treatment modalities and bridges the gap between scientific advancement and clinical practice in AA and vitiligo management.

Characterization of the dual ITK/JAK3 small molecule covalent inhibitor ATI-2138

Aclaris Therapeutics Inc (ATI)-2138 is a novel investigational covalent inhibitor of interleukin-2-inducible T cell kinase (ITK), resting lymphocyte kinase, and Janus kinase 3 (JAK3) in development for the treatment of autoimmune and inflammatory diseases. In this study, we evaluated the inhibitory effects of ATI-2138 on ITK and JAK3 signaling in cells and preclinical animal models and assessed the safety, tolerability, pharmacokinetics, and pharmacodynamics of ATI-2138 in healthy human participants. ATI-2138 potently, selectively, and irreversibly inhibited ITK, resting lymphocyte kinase, and JAK3 kinases with similar potency observed against ITK and JAK3 in biochemical and immune cell signaling assays. Translation from cellular and whole blood studies to in vivo models was observed, wherein ATI-2138 demonstrated disease-modifying activity in 2 rodent models of arthritis and an adoptive T cell model of colitis. In single and multiple ascending dose studies in healthy human participants, ATI-2138 had a favorable safety profile with linear pharmacokinetics. Biomarkers linked to both ITK and JAK3 activity were inhibited with ATI-2138 in an exposure-, dose-, and time-dependent manner and correlated with enzyme, cellular, whole blood, and rodent studies, thereby demonstrating predictive translational properties. As a potential first-in-class dual inhibitor of ITK and JAK3, ATI-2138 may be useful in the treatment of immunoinflammatory diseases. SIGNIFICANCE STATEMENT: Aclaris Therapeutics Inc (ATI)-2138 is a novel covalent inhibitor of interleukin-2-inducible T cell kinase (ITK)/resting lymphocyte kinase and Janus kinase 3 (JAK3). ATI-2138 inhibits JAK3 and ITK in enzyme and functional cellular assays, demonstrates disease-modifying activity in rodent models of arthritis and colitis, and inhibits biomarkers linked to both ITK and JAK3 activity in healthy human participants. With this dual kinase activity against components of these inflammatory signaling pathway, ATI-2138 has the potential for enhanced therapeutic efficacy in the treatment of autoimmune and chronic inflammatory disease.

VAV1 as a putative therapeutic target in autoimmune and chronic inflammatory diseases

The guanine nucleotide exchange factor (GEF) VAV1, a previously 'undruggable' protein integral to T/B lymphocyte antigen-receptor signaling, promotes actin polymerization, immunological synapse formation, T cell activation and differentiation, and cytokine production. With the development of novel modalities for targeting proteins, we hypothesize that interventions targeting VAV1 will have therapeutic potential in T and T/B cell-mediated autoimmune and chronic inflammatory diseases. This opinion is supported by recent CRISPR-Cas9 studies showing VAV1 as a key positive regulator of T cell receptor (TCR) activation and cytokine production in primary human CD4+ and CD8+ T cells; data demonstrating that loss/suppression of VAV1 regulates autoimmunity and inflammation; and promising preclinical data from T and T/B cell-mediated disease models of arthritis and colitis showing the effectiveness of selective VAV1 targeting via protein degradation.

The PI3K signaling pathway; from normal lymphopoiesis to lymphoid malignancies

INTRODUCTION

As a vital mechanism of survival, lymphopoiesis requires the collaboration of different signaling molecules to orchestrate each step of cell development and maturation. The PI3K pathway is considerably involved in the maturation of lymphatic cells and therefore, its dysregulation can immensely affect human well-being and cause some of the most prevalent malignancies. As a result, studies that investigate this pathway could pave the way for a better understanding of the lymphopoiesis mechanisms, the undesired changes that lead to cancer progression, and how to design drugs to solve this issue.

AREAS COVERED

The present review addresses the aforementioned aspects of the PI3K pathway and helps pave the way for future therapeutic approaches. In order to access the articles, databases such as Medicine Medline/PubMed, Scopus, Google Scholar, and Science Direct were utilized. The search formula was established by identifying main keywords including PI3K/Akt/mTOR pathway, Lymphopoiesis, Lymphoid malignancies, and inhibitors.

EXPERT OPINION

The PI3K pathway is crucial for lymphocyte development and differentiation, making it a potential target for therapeutic intervention in lymphoid cancers. Studies are focused on developing PI3K inhibitors to impede the progression of hematologic malignancies, highlighting the pathway's significance in lymphoma and lymphoid leukemia.

Interaction of T-cell-specific adapter protein with Src- and Tec-family kinases

Adapter proteins are flexible and dynamic modulators of cellular signalling that are important for immune cell function. One of these, the T-cell-specific adapter protein (TSAd), interacts with the non-receptor tyrosine kinases Src and Lck of the Src family kinases (SFKs) and Itk of the Tec family kinases (TFKs). Three tyrosine residues in the TSAd C-terminus are phosphorylated by Lck and serve as docking sites for the Src homology 2 (SH2) domains of Src and Lck. The TSAd proline-rich region (PRR) binds to the Src homology 3 (SH3) domains found in Lck, Src and Itk. Despite known interactors, the role TSAd plays in cellular signalling remains largely unknown. TSAd's ability to bind both SFKs and TFKs may point to its function as a general scaffold for both kinase families. Using GST-pulldown as well as peptide array experiments, we found that both the SH2 and SH3 domains of the SFKs Fyn and Hck, as well as the TFKs Tec and Txk, interact with TSAd. This contrasts with Itk, which interacts with TSAd only through its SH3 domain. Although our analysis showed that TSAd is both co-expressed and may interact with Fyn, we were unable to co-precipitate Fyn with TSAd from Jurkat cells, as detected by Western blotting and affinity purification mass spectrometry. This may suggest that TSAd-Fyn interaction in intact cells may be limited by other factors, such as the subcellular localization of the two molecules or the co-expression of competing binding partners.

Adaptive immune cells are necessary for SARS-CoV-2-induced pathology

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is causing the ongoing global pandemic associated with morbidity and mortality in humans. Although disease severity correlates with immune dysregulation, the cellular mechanisms of inflammation and pathogenesis of COVID-19 remain relatively poorly understood. Here, we used mouse-adapted SARS-CoV-2 strain MA10 to investigate the role of adaptive immune cells in disease. We found that while infected wild-type mice lost ~10% weight by 3 to 4 days postinfection, rag-/- mice lacking B and T lymphocytes did not lose weight. Infected lungs at peak weight loss revealed lower pathology scores, fewer neutrophils, and lower interleukin-6 and tumor necrosis factor-α in rag-/- mice. Mice lacking αβ T cells also had less severe weight loss, but adoptive transfer of T and B cells into rag-/- mice did not significantly change the response. Collectively, these findings suggest that while adaptive immune cells are important for clearing SARS-CoV-2 infection, this comes at the expense of increased inflammation and pathology.

Cytokine Storm Syndromes Associated with Epstein-Barr Virus

Epstein-Barr virus (EBV) is a ubiquitous and predominantly B cell tropic virus. One of the most common viruses to infect humans, EBV, is best known as the causative agent of infectious mononucleosis (IM). Although most people experience asymptomatic infection, EBV is a potent immune stimulus and as such it elicits robust proliferation and activation of the B-lymphocytes it infects as well as the immune cells that respond to infection. In certain individuals, such as those with inherited or acquired defects affecting the immune system, failure to properly control EBV leads to the accumulation of EBV-infected B cells and EBV-reactive immune cells, which together contribute to the development of often life-threatening cytokine storm syndromes (CSS). Here, we review the normal immune response to EBV and discuss several CSS associated with EBV, such as chronic active EBV infection, hemophagocytic lymphohistiocytosis, and post-transplant lymphoproliferative disorder. Given the critical role for cytokines in driving inflammation and contributing to disease pathogenesis, we also discuss how targeting specific cytokines provides a rational and potentially less toxic treatment for EBV-driven CSS.

Targeting kinase ITK treats autoimmune arthritis via orchestrating T cell differentiation and function

IL-2 inducible T cell kinase (ITK) is critical in T helper subset differentiation and its inhibition has been suggested for the treatment of T cell-mediated inflammatory diseases. T follicular helper (Tfh), Th17 and regulatory T cells (Treg) also play important roles in the development of rheumatoid arthritis (RA), while the role of ITK in the development of RA and the intricate balance between effector T and regulatory T cells remains unclear. Here, we found that CD4+ T cells from RA patients presented with an elevated ITK activation. ITK inhibitor alleviated existing collagen-induced arthritis (CIA) and reduced antigen specific antibody production. Blocking ITK kinase activity interferes Tfh cell generation. Moreover, ITK inhibitor effectively rebalances Th17 and Treg cells by regulating Foxo1 translocation. Furthermore, we identified dihydroartemisinin (DHA) as a potential ITK inhibitor, which could inhibit PLC-γ1 phosphorylation and the progression of CIA by rebalancing Th17 and Treg cells. Out data imply that ITK activation is upregulated in RA patients, and therefore blocking ITK signal may provide an effective strategy to treat RA patients and highlight the role of ITK on the Tfh induction and RA progression.

Activation Mechanisms and Diverse Functions of Mammalian Phospholipase C

Phospholipase C (PLC) plays pivotal roles in regulating various cellular functions by metabolizing phosphatidylinositol 4,5-bisphosphate in the plasma membrane. This process generates two second messengers, inositol 1,4,5-trisphosphate and diacylglycerol, which respectively regulate the intracellular Ca²⁺ levels and protein kinase C activation. In mammals, six classes of typical PLC have been identified and classified based on their structure and activation mechanisms. They all share X and Y domains, which are responsible for enzymatic activity, as well as subtype-specific domains. Furthermore, in addition to typical PLC, atypical PLC with unique structures solely harboring an X domain has been recently discovered. Collectively, seven classes and 16 isozymes of mammalian PLC are known to date. Dysregulation of PLC activity has been implicated in several pathophysiological conditions, including cancer, cardiovascular diseases, and neurological disorders. Therefore, identification of new drug targets that can selectively modulate PLC activity is important. The present review focuses on the structures, activation mechanisms, and physiological functions of mammalian PLC.

Bruton tyrosine kinase inhibitors for multiple sclerosis

Current therapies for multiple sclerosis (MS) reduce both relapses and relapse-associated worsening of disability, which is assumed to be mainly associated with transient infiltration of peripheral immune cells into the central nervous system (CNS). However, approved therapies are less effective at slowing disability accumulation in patients with MS, in part owing to their lack of relevant effects on CNS-compartmentalized inflammation, which has been proposed to drive disability. Bruton tyrosine kinase (BTK) is an intracellular signalling molecule involved in the regulation of maturation, survival, migration and activation of B cells and microglia. As CNS-compartmentalized B cells and microglia are considered central to the immunopathogenesis of progressive MS, treatment with CNS-penetrant BTK inhibitors might curtail disease progression by targeting immune cells on both sides of the blood-brain barrier. Five BTK inhibitors that differ in selectivity, strength of inhibition, binding mechanisms and ability to modulate immune cells within the CNS are currently under investigation in clinical trials as a treatment for MS. This Review describes the role of BTK in various immune cells implicated in MS, provides an overview of preclinical data on BTK inhibitors and discusses the (largely preliminary) data from clinical trials.

Bruton tyrosine kinase inhibitors preserve anti-CD19 chimeric antigen receptor T-cell functionality and reprogram tumor micro-environment in B-cell lymphoma

BACKGROUND AIMS

Combination therapy is being actively explored to improve the efficacy and safety of anti-CD19 chimeric antigen receptor T-cell (CART19) therapy, among which Bruton tyrosine kinase inhibitors (BTKIs) are highly expected. BTKIs may modulate T-cell function and remodel the tumor micro-environment (TME), but the exact mechanisms involved and the steps required to transform different BTKIs into clinical applications need further investigation.

METHODS

We examined the impacts of BTKIs on T-cell and CART19 phenotype and functionality in vitro and further explored the mechanisms. We evaluated the efficacy and safety of CART19 concurrent with BTKIs in vitro and in vivo. Moreover, we investigated the effects of BTKIs on TME in a syngeneic lymphoma model.

RESULTS

Here we identified that the three BTKIs, ibrutinib, zanubrutinib and orelabrutinib, attenuated CART19 exhaustion mediated by tonic signaling, T-cell receptor (TCR) activation and antigen stimulation. Mechanistically, BTKIs markedly suppressed CD3-ζ phosphorylation of both chimeric antigen receptor and TCR and downregulated the expression of genes associated with T-cell activation signaling pathways. Moreover, BTKIs decreased interleukin 6 and tumor necrosis factor alpha release in vitro and in vivo. In a syngeneic lymphoma model, BTKIs reprogrammed macrophages to the M1 subtype and polarized T helper (Th) cells toward the Th1 subtype.

CONCLUSIONS

Our data revealed that BTKIs preserved T-cell and CART19 functionality under persistent antigen exposure and further demonstrated that BTKI administration was a potential strategy for mitigating cytokine release syndrome after CART19 treatment. Our study lays the experimental foundation for the rational application of BTKIs combined with CART19 in clinical practice.

Cyclophilin A associates with and regulates the activity of ZAP70 in TCR/CD3-stimulated T cells

The ZAP70 protein tyrosine kinase (PTK) couples stimulated T cell antigen receptors (TCRs) to their downstream signal transduction pathways and is sine qua non for T cell activation and differentiation. TCR engagement leads to activation-induced post-translational modifications of ZAP70, predominantly by kinases, which modulate its conformation, leading to activation of its catalytic domain. Here, we demonstrate that ZAP70 in TCR/CD3-activated mouse spleen and thymus cells, as well as human Jurkat T cells, is regulated by the peptidyl-prolyl cis-trans isomerase (PPIase), cyclophilin A (CypA) and that this regulation is abrogated by cyclosporin A (CsA), a CypA inhibitor. We found that TCR crosslinking promoted a rapid and transient, Lck-dependent association of CypA with the interdomain B region, at the ZAP70 regulatory domain. CsA inhibited CypA binding to ZAP70 and prevented the colocalization of CypA and ZAP70 at the cell membrane. In addition, imaging analyses of antigen-specific T cells stimulated by MHC-restricted antigen-fed antigen-presenting cells revealed the recruitment of ZAP70-bound CypA to the immunological synapse. Enzymatically active CypA downregulated the catalytic activity of ZAP70 in vitro, an effect that was reversed by CsA in TCR/CD3-activated normal T cells but not in CypA-deficient T cells, and further confirmed in vivo by FRET-based studies. We suggest that CypA plays a role in determining the activity of ZAP70 in TCR-engaged T cells and impact on T cell activation by intervening with the activity of multiple downstream effector molecules.

GATA-3 is a proto-oncogene in T-cell lymphoproliferative neoplasms

Neoplasms originating from thymic T-cell progenitors and post-thymic mature T-cell subsets account for a minority of lymphoproliferative neoplasms. These T-cell derived neoplasms, while molecularly and genetically heterogeneous, exploit transcription factors and signaling pathways that are critically important in normal T-cell biology, including those implicated in antigen-, costimulatory-, and cytokine-receptor signaling. The transcription factor GATA-3 regulates the growth and proliferation of both immature and mature T cells and has recently been implicated in T-cell neoplasms, including the most common mature T-cell lymphoma observed in much of the Western world. Here we show that GATA-3 is a proto-oncogene across the spectrum of T-cell neoplasms, including those derived from T-cell progenitors and their mature progeny, and further define the transcriptional programs that are GATA-3 dependent, which include therapeutically targetable gene products. The discovery that p300-dependent acetylation regulates GATA-3 mediated transcription by attenuating DNA binding has novel therapeutic implications. As most patients afflicted with GATA-3 driven T-cell neoplasms will succumb to their disease within a few years of diagnosis, these findings suggest opportunities to improve outcomes for these patients.

Interleukin-2 inducible T cell kinase (ITK) may participate in the anti-bacterial immune response of Nile tilapia via regulating T-cell activation

Interleukin-2 inducible T cell kinase (ITK) plays a predominant role in the T-cell receptor (TCR) signaling cascade to ensure valid T-cell activation and function. Nevertheless, whether it regulates T-cell response of early vertebrates remains unknown. Herein, we investigated the involvement of ITK in the lymphocyte-mediated adaptive immune response, and its regulation to T-cell activation in the Nile tilapia Oreochromis niloticus. Both sequence and structure of O. niloticus ITK (OnITK) were remarkably conserved with its homologues from other vertebrates, implying its potential conserved function. OnITK mRNA was extensively expressed in lymphoid-related tissues, and with the relative highest level in peripheral blood. Once Nile tilapia was infected by Edwardsiella piscicida, OnITK in splenic lymphocytes was significantly up-regulated on 7-day post infection at both transcription and translation levels, suggesting that OnITK might involve in the primary adaptive immune response of teleost. Furthermore, upon splenic lymphocytes were stimulated by T-cell specific mitogen PHA, OnITK mRNA and protein levels were dramatically elevated. More importantly, treatment of splenic lymphocytes with specific inhibitor significantly crippled OnITK expression, which in turn impaired the inducible expression of T-cell activation markers IFN-γ, IL-2 and CD122, indicating the critical roles of ITK in regulating T-cell activation of Nile tilapia. Taken together, our results suggest that ITK takes part in the lymphocyte-mediated adaptive immunity of tilapia, and is indispensable for T-cell activation of teleost. Our findings thus provide novel evidences for understanding the mechanism regulating T-cell immunity of early vertebrates, as well as the evolution of adaptive immune system.

Reciprocal SH2-SH3 Domain Contacts between ITK Molecules Limit T Cell Receptor Signaling in Th2-type CD4+ T Cells

The nonreceptor tyrosine kinase ITK is a key component of the T cell receptor (TCR) signaling pathway and is required for cytokine production by CD4⁺ T cells that have differentiated into Th2 cells. Structural and biochemical studies suggest that contacts between the SH2 and SH3 domains of ITK mediate intermolecular self-association, forming a structure that restrains ITK activity by interfering with interactions between ITK and other components of the TCR signaling pathway. Wild-type (WT) ITK and a panel of ITK mutants containing amino acid substitutions in the SH2 and SH3 domains were tested for self-association and for binding to the adaptor protein SLP76, a key ligand for the ITK SH2 domain. WT and ITK mutants were also expressed in Itk-deficient CD4⁺ T cells via retroviral-mediated gene delivery to analyze their ability to support TCR signaling and cytokine production by Th2 cells. Specific amino acid substitutions in the ITK SH2 or SH3 domains impaired self-association, with the greatest effects being seen when both intermolecular SH2-SH3 domain contacts were disrupted. Two of the SH2 domain substitutions tested reduced ITK self-association but had no effect on binding to SLP-76. When their function was analyzed in Th2 cells, ITK proteins with diminished self-association activity supported greater IL-4 production and calcium flux in response to TCR stimulation compared to WT ITK. Our findings indicate that intermolecular contacts between ITK molecules can restrain the amplitude of TCR signaling, suggesting ITK is a limiting factor for responses by CD4+ T cells.

Dynamics of allosteric regulation of the phospholipase C-γ isozymes upon recruitment to membranes

Numerous receptor tyrosine kinases and immune receptors activate phospholipase C-γ (PLC-γ) isozymes at membranes to control diverse cellular processes including phagocytosis, migration, proliferation, and differentiation. The molecular details of this process are not well understood. Using hydrogen-deuterium exchange mass spectrometry, we show that PLC-γ1 is relatively inert to lipid vesicles that contain its substrate, phosphatidylinositol 4,5-bisphosphate (PIP₂), unless first bound to the kinase domain of the fibroblast growth factor receptor (FGFR1). Exchange occurs throughout PLC-γ1 and is exaggerated in PLC-γ1 containing an oncogenic substitution (D1165H) that allosterically activates the lipase. These data support a model whereby initial complex formation shifts the conformational equilibrium of PLC-γ1 to favor activation. This receptor-induced priming of PLC-γ1 also explains the capacity of a kinase-inactive fragment of FGFR1 to modestly enhance the lipase activity of PLC-γ1 operating on lipid vesicles but not a soluble analog of PIP₂ and highlights potential cooperativity between receptor engagement and membrane proximity. Priming is expected to be greatly enhanced for receptors embedded in membranes and nearly universal for the myriad of receptors and co-receptors that bind the PLC-γ isozymes.

Recognition of Immune Cell Markers of COVID-19 Severity with Machine Learning Methods

COVID-19 is hypothesized to be linked to the host's excessive inflammatory immunological response to SARS-CoV-2 infection, which is regarded to be a major factor in disease severity and mortality. Numerous immune cells play a key role in immune response regulation, and gene expression analysis in these cells could be a useful method for studying disease states, assessing immunological responses, and detecting biomarkers. Here, we developed a machine learning procedure to find biomarkers that discriminate disease severity in individual immune cells (B cell, CD4+ cell, CD8+ cell, monocyte, and NK cell) using single-cell gene expression profiles of COVID-19. The gene features of each profile were first filtered and ranked using the Boruta feature selection method and mRMR, and the resulting ranked feature lists were then fed into the incremental feature selection method to determine the optimal number of features with decision tree and random forest algorithms. Meanwhile, we extracted the classification rules in each cell type from the optimal decision tree classifiers. The best gene sets discovered in this study were analyzed by GO and KEGG pathway enrichment, and some important biomarkers like TLR2, ITK, CX3CR1, IL1B, and PRDM1 were validated by recent literature. The findings reveal that the optimal gene sets for each cell type can accurately classify COVID-19 disease severity and provide insight into the molecular mechanisms involved in disease progression.

Distinguishing activated T regulatory cell and T conventional cells by single cell technologies

Resting conventional T cells (Tconv) can be distinguished from T regulatory cells (Treg) by the canonical markers FOXP3, CD25 and CD127. However, the expression of these proteins alters after T‐cell activation leading to overlap between Tconv and Treg. The objective of this study was to distinguish resting and antigen‐responsive T effector (Tconv) and Treg using single‐cell technologies. CD4⁺ Treg and Tconv cells were stimulated with antigen and responsive and non‐responsive populations processed for targeted and non‐targeted single‐cell RNAseq. Machine learning was used to generate a limited set of genes that could distinguish responding and non‐responding Treg and Tconv cells and which was used for single‐cell multiplex qPCR and to design a flow cytometry panel. Targeted scRNAseq clearly distinguished the four‐cell populations. A minimal set of 27 genes was identified by machine learning algorithms to provide discrimination of the four populations at >95% accuracy. In all, 15 of the genes were validated to be differentially expressed by single‐cell multiplex qPCR. Discrimination of responding Treg from responding Tconv could be achieved by a flow cytometry strategy that included staining for CD25, CD127, FOXP3, IKZF2, ITGA4, and the novel marker TRIM which was strongly expressed in Tconv and weakly expressed in both responding and non‐responding Treg. A minimal set of genes was identified that discriminates responding and non‐responding CD4⁺ Treg and Tconv cells and, which have identified TRIM as a marker to distinguish Treg by flow cytometry.

T cell receptor (TCR) signaling in health and disease

Interaction of the T cell receptor (TCR) with an MHC-antigenic peptide complex results in changes at the molecular and cellular levels in T cells. The outside environmental cues are translated into various signal transduction pathways within the cell, which mediate the activation of various genes with the help of specific transcription factors. These signaling networks propagate with the help of various effector enzymes, such as kinases, phosphatases, and phospholipases. Integration of these disparate signal transduction pathways is done with the help of adaptor proteins that are non-enzymatic in function and that serve as a scaffold for various protein-protein interactions. This process aids in connecting the proximal to distal signaling pathways, thereby contributing to the full activation of T cells. This review provides a comprehensive snapshot of the various molecules involved in regulating T cell receptor signaling, covering both enzymes and adaptors, and will discuss their role in human disease.

Cytotoxic lymphocytes-related gene ITK from a systematic CRISPR screen could predict prognosis of ovarian cancer patients with distant metastasis

Background

Ovarian cancer, a highly metastatic malignancy, has benefited tremendously from advances in modern human genomics. However, the genomic variations related to the metastasis remains unclear.

Methods

We filtered various significant genes (n = 6722) associated with metastasis within a large-scale functional genomic CRISPR/Cas9 knock-out library including 122,756 single guide RNAs, and identified ITK (IL2 Inducible T Cell Kinase) as a potential cancer suppressor gene for ovarian cancer metastasis. Downstream bioinformatic analysis was performed for ITK using public databases.

Results

We found that patients in low-ITK group had poor prognosis and more distant metastasis than those in high-ITK group in TCGA and GEO databases. We also demonstrated that ITK combined with the clinical factors could accurately predict prognosis through multiple Cox regression analysis and ROC analysis. Moreover, alterations correlated with distant metastasis emereged with significantly increased expression in SAMRCD1 in low-ITK group, but CD244 and SOCS1 in high-ITK group. Integrated analysis revealed dysregulated molecular processes including predominantly oncogenic signaling pathways in low-ITK group but immune related pathways in high-ITK group, which suggested ITK might inhibit distant metastasis in ovarian cancer. Furtherly, deconvolution of the cellular composition of all samples validated the close correlation between ITK and immune related function especially for cytotoxic lymphocytes.

Conclusions

Together, these data provide insights into the potential role of ITK, with implications for the future development of tansformative ovarian cancer therapeutics.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-03119-3.

Current progress, challenges and future prospects of indazoles as protein kinase inhibitors for the treatment of cancer

The indazole core is an interesting pharmacophore due to its applications in medicinal chemistry. In the past few years, this moiety has been used for the synthesis of kinase inhibitors. Many researchers have demonstrated the use of indazole derivatives as specific kinase inhibitors, including tyrosine kinase and serine/threonine kinases. A number of anticancer drugs with an indazole core are commercially available, e.g. axitinib, linifanib, niraparib, and pazopanib. Indazole derivatives are applied for the targeted treatment of lung, breast, colon, and prostate cancers. In this review, we compile the current development of indazole derivatives as kinase inhibitors and their application as anticancer agents in the past five years.

How the Discovery of the CD4/CD8-p56lck Complexes Changed Immunology and Immunotherapy

The past 25 years have seen enormous progress in uncovering the receptors and signaling mechanisms on T-cells that activate their various effecter functions. Until the late 1980s, most studies on T-cells had focused on the influx of calcium and the levels of cAMP/GMP in T-cells. My laboratory then uncovered the interaction of CD4 and CD8 co-receptors with the protein-tyrosine kinase p56lck which are now widely accepted as the initiators of the tyrosine phosphorylation cascade leading to T-cell activation. The finding explained how immune recognition receptors expressed by many immune cells, which lack intrinsic catalytic activity, can transduce activation signals via non-covalent association with non-receptor tyrosine kinases. The discovery also established the concept that a protein tyrosine phosphorylation cascade operated in T-cells. In this vein, we and others then showed that the CD4- and CD8-p56lck complexes phosphorylate the TCR complexes which led to the identification of other protein-tyrosine kinases such as ZAP-70 and an array of substrates that are now central to studies in T-cell immunity. Other receptors such as B-cell receptor, Fc receptors and others were also subsequently found to use src kinases to control cell growth. In T-cells, p56lck driven phosphorylation targets include co-receptors such as CD28 and CTLA-4 and immune cell-specific adaptor proteins such as LAT and SLP-76 which act to integrate signals proximal to surface receptors. CD4/CD8-p56lck regulated events in T-cells include intracellular calcium mobilization, integrin activation and the induction of transcription factors for gene expression. Lastly, the identification of the targets of p56lck in the TCR and CD28 provided the framework for the development of chimeric antigen receptor (CAR) therapy in the treatment of cancer. In this review, I outline a history of the development of events that led to the development of the "TCR signaling paradigm" and its implications to immunology and immunotherapy.

A Novel, LAT/Lck Double Deficient T Cell Subline J.CaM1.7 for Combined Analysis of Early TCR Signaling

Intracellular signaling through the T cell receptor (TCR) is essential for T cell development and function. Proper TCR signaling requires the sequential activities of Lck and ZAP-70 kinases, which result in the phosphorylation of tyrosine residues located in the CD3 ITAMs and the LAT adaptor, respectively. LAT, linker for the activation of T cells, is a transmembrane adaptor protein that acts as a scaffold coupling the early signals coming from the TCR with downstream signaling pathways leading to cellular responses. The leukemic T cell line Jurkat and its derivative mutants J.CaM1.6 (Lck deficient) and J.CaM2 (LAT deficient) have been widely used to study the first signaling events upon TCR triggering. In this work, we describe the loss of LAT adaptor expression found in a subline of J.CaM1.6 cells and analyze cis-elements responsible for the LAT expression defect. This new cell subline, which we have called J.CaM1.7, can re-express LAT adaptor after Protein Kinase C (PKC) activation, which suggests that activation-induced LAT expression is not affected in this new cell subline. Contrary to J.CaM1.6 cells, re-expression of Lck in J.CaM1.7 cells was not sufficient to recover TCR-associated signals, and both LAT and Lck had to be introduced to recover activatory intracellular signals triggered after CD3 crosslinking. Overall, our work shows that the new LAT negative J.CaM1.7 cell subline could represent a new model to study the functions of the tyrosine kinase Lck and the LAT adaptor in TCR signaling, and their mutual interaction, which seems to constitute an essential early signaling event associated with the TCR/CD3 complex.

Guiding Medicinal Chemistry with Fragment Molecular Orbital (FMO) Method

The understanding of binding interactions between a protein and a small molecule plays a key role in the rationalization of potency and selectivity and in design of new ideas. However, even when a target of interest is structurally enabled, visual inspection and force field-based molecular mechanics calculations cannot always explain the full complexity of the molecular interactions that are critical in drug design. Quantum mechanical methods have the potential to address this shortcoming, but traditionally, computational expense has made the application of these calculations impractical. The fragment molecular orbital (FMO) method offers a solution that combines accuracy, speed, and the ability to characterize important interactions (i.e. its strength in kcal/mol and chemical nature: hydrophobic, electrostatic, etc) that would otherwise be hard to detect. In this chapter, we describe the FMO method and illustrate its application in the discovery of the benzothiazole (BZT) series as novel tyrosine kinase ITK inhibitors for treatment of allergic asthma.

Topical Application of BMS-509744, a Selective Inhibitor of Interleukin-2-Inducible T Cell Kinase, Ameliorates Imiquimod-Induced Skin Inflammation in Mice

Psoriasis is an immune disorder-related inflammatory skin disease. Recent studies have suggested a contribution of T cell activation in the pathogenesis of psoriasis. Interleukin-2 (IL-2)-inducible T cell kinase (ITK) regulates T cell activation, including proliferation, and cytokine production. In this study, we investigated the effect of the topically administered selective ITK inhibitor BMS-509744 on imiquimod (IMQ)-induced psoriasis-like skin inflammation in mice. Topically administered BMS-509744 ameliorated IMQ-induced psoriasis-like skin inflammation as shown by decreased skin lesions, epidermal thickening, and cell infiltration into the dermis. These suppressive effects occurred with lower numbers of cluster of differentiation antigen-3⁺ (CD3⁺) T cells and T helper subset 17 (Th17)-related cytokine expression in IMQ-treated skin. IMQ-induced upregulation of proinflammatory cytokine expression was also inhibited by topical application of BMS-509744 in IMQ-treated skin. Our report showed for the first time that topical application of BMS-509744 ameliorated psoriasis-like skin inflammation in mice, which is likely mediated by the inhibition of T cell activation in the skin lesions.

TCR/ITK Signaling in Type 1 Regulatory T cells

Type 1 regulatory T (Tr1) cells can modulate inflammation through multiple direct and indirect molecular and cellular mechanisms and have demonstrated potential for anti-inflammatory therapies. Tr1 cells do not express the master transcription factor of conventional regulatory T cells, Foxp3, but express high levels of the immunomodulatory cytokine, IL-10. IL-2-inducible T-cell kinase (ITK) is conserved between mouse and human and is highly expressed in T cells. ITK signaling downstream of the T-cell receptor (TCR) is critical for T-cell subset differentiation and function. Upon activation by TCR, ITK is critical for Ras activation, leading to downstream activation of MAPKs and upregulation of IRF4, which further enable Tr1 cell differentiation and suppressive function. We summarize here the structure, signaling pathway, and function of ITK in T-cell lineage designation, with an emphasis on Tr1 cell development and function.

Targeting Interleukin-2-Inducible T-Cell Kinase (ITK) Differentiates GVL and GVHD in Allo-HSCT

Allogeneic hematopoietic stem cell transplantation is a potentially curative procedure for many malignant diseases. Donor T cells prevent disease recurrence via graft-versus-leukemia (GVL) effect. Donor T cells also contribute to graft-versus-host disease (GVHD), a debilitating and potentially fatal complication. Novel treatment strategies are needed which allow preservation of GVL effects without causing GVHD. Using murine models, we show that targeting IL-2-inducible T cell kinase (ITK) in donor T cells reduces GVHD while preserving GVL effects. Both CD8⁺ and CD4⁺ donor T cells from Itk^-/- mice produce less inflammatory cytokines and show decrease migration to GVHD target organs such as the liver and small intestine, while maintaining GVL efficacy against primary B-cell acute lymphoblastic leukemia (B-ALL). Itk^-/- T cells exhibit reduced expression of IRF4 and decreased JAK/STAT signaling activity but upregulating expression of Eomesodermin (Eomes) and preserve cytotoxicity, necessary for GVL effect. Transcriptome analysis indicates that ITK signaling controls chemokine receptor expression during alloactivation, which in turn affects the ability of donor T cells to migrate to GVHD target organs. Our data suggest that inhibiting ITK could be a therapeutic strategy to reduce GVHD while preserving the beneficial GVL effects following allo-HSCT treatment.

Emerging Kinase Therapeutic Targets in Pancreatic Ductal Adenocarcinoma and Pancreatic Cancer Desmoplasia

Kinase drug discovery represents an active area of therapeutic research, with previous pharmaceutical success improving patient outcomes across a wide variety of human diseases. In pancreatic ductal adenocarcinoma (PDAC), innovative pharmaceutical strategies such as kinase targeting have been unable to appreciably increase patient survival. This may be due, in part, to unchecked desmoplastic reactions to pancreatic tumors. Desmoplastic stroma enhances tumor development and progression while simultaneously restricting drug delivery to the tumor cells it protects. Emerging evidence indicates that many of the pathologic fibrotic processes directly or indirectly supporting desmoplasia may be driven by targetable protein tyrosine kinases such as Fyn-related kinase (FRK); B lymphoid kinase (BLK); hemopoietic cell kinase (HCK); ABL proto-oncogene 2 kinase (ABL2); discoidin domain receptor 1 kinase (DDR1); Lck/Yes-related novel kinase (LYN); ephrin receptor A8 kinase (EPHA8); FYN proto-oncogene kinase (FYN); lymphocyte cell-specific kinase (LCK); tec protein kinase (TEC). Herein, we review literature related to these kinases and posit signaling networks, mechanisms, and biochemical relationships by which this group may contribute to PDAC tumor growth and desmoplasia.

Transcriptome analyses provide insights into maternal immune changes at several critical phases of giant panda reproduction

Giant pandas (Ailuropoda melanoleuca) possess highly specialized reproductive characteristics, but the maternal immune changes during reproduction are largely unclear. Here, 20 blood transcriptomes were used to determine immune changes at four key phases of giant panda reproduction, and a total of 4640 differential expression genes were identified. During estrus, six immune-related genes (TLR4, IL1B, SYK, SPI1, CD80, and ITK) were identified as hub genes. The up-regulation of the TLR family genes (TLR4, TLR5, TLR6, and TLR8) and inflammatory response related genes (IL1B) may reflect innate immune enhancement and local tissue remodeling events, while the up-regulation of SYK and SPI1, and the down-regulation of CD80 and ITK suggested that the enhanced humoral immunity and inhibited cellular immunity of female giant pandas during estrus. During early pregnancy, antigen presentation related genes and proinflammatory cytokine (IL1B) were down-regulated. This may indicate that partial immune functions were suppressed in early pregnancy to achieve immune tolerance, including reducing inflammatory to protect embryos. By the late pregnancy, the antiviral related genes were up-regulated to strengthen defenses against external pathogen infection. KLRK1, which acts as a primary activation receptor for NK cells, was down regulated in estrus and pregnancy, suggesting that the activities of NK cells were inhibited, and KLRK1 may play a key role in the regulation the activities of pbNK cells during reproduction of giant pandas. Our results showed that there was no significant immune change in lactating females (post-natal 2 months) compared to anestrus females. This is the first time to observe the immune changes of giant panda during the breeding period and our data is expected to provide valuable resources for further studies on reproductive immunology of giant pandas.

Role of the IL-2 inducible tyrosine kinase ITK and its inhibitors in disease pathogenesis

ITK (IL-2-inducible tyrosine kinase) belongs to the Tec family kinases and is mainly expressed in T cells. It is involved in TCR signalling events driving processes like T cell development as well as Th2, Th9 and Th17 responses thereby controlling the expression of pro-inflammatory cytokines. Studies have shown that ITK is involved in the pathogenesis of autoimmune diseases as well as in carcinogenesis. The loss of ITK or its activity either by mutation or by the use of inhibitors led to a beneficial outcome in experimental models of asthma, inflammatory bowel disease and multiple sclerosis among others. In humans, biallelic mutations in the ITK gene locus result in a monogenetic disorder leading to T cell dysfunction; in consequence, mainly EBV infections can lead to severe immune dysregulation evident by lymphoproliferation, lymphoma and hemophagocytic lymphohistiocytosis. Furthermore, patients who suffer from angioimmunoblastic T cell lymphoma have been found to express significantly more ITK. These findings put ITK in the strong focus as a target for drug development.

Tuning T helper cell differentiation by ITK

CD4+ effector T cells effectuate T cell immune responses, producing cytokines to orchestrate the nature and type of immune responses. The non-receptor tyrosine kinase IL-2 inducible T cell kinase (ITK), a mediator of T cell Receptor signaling, plays a critical role in tuning the development of these effector cells. In this review we discussed the role that signals downstream of ITK, including the Ras/MAPK pathway, play in differentially controlling the differentiation of TH17, Foxp3+ T regulatory (Treg) cells, and Type 1 regulatory T (Tr1) cells, supporting a model of ITK signals controlling a decision point in the effector T cell differentiation process.

Signaling pathways involved in the T-cell-mediated immunity against Epstein-Barr virus: Lessons from genetic diseases

Primary immunodeficiencies (PIDs) provide researchers with unique models to understand in vivo immune responses in general and immunity to infections in particular. In humans, impaired immune control of Epstein-Barr virus (EBV) infection is associated with the occurrence of several different immunopathologic conditions; these include non-malignant and malignant B-cell lymphoproliferative disorders, hemophagocytic lymphohistiocytosis (HLH), a severe inflammatory condition, and a chronic acute EBV infection of T cells. Studies of PIDs associated with a predisposition to develop severe, chronic EBV infections have led to the identification of key components of immunity to EBV - notably the central role of T-cell expansion and its regulation in the pathophysiology of EBV-associated diseases. On one hand, the defective expansion of EBV-specific CD8 T cells results from mutations in genes involved in T-cell activation (such as RASGRP1, MAGT1, and ITK), DNA metabolism (CTPS1) or co-stimulatory pathways (CD70, CD27, and TNFSFR9 (also known as CD137/4-1BB)) leads to impaired elimination of proliferating EBV-infected B cells and the occurrence of lymphoma. On the other hand, protracted T-cell expansion and activation after the defective killing of EBV-infected B cells is caused by genetic defects in the components of the lytic granule exocytosis pathway or in the small adapter protein SH2D1A (also known as SAP), a key activator of T- and NK cell-cytotoxicity. In this setting, the persistence of EBV-infected cells results in HLH, a condition characterized by unleashed T-cell and macrophage activation. Moreover, genetic defects causing selective vulnerability to EBV infection have highlighted the role of co-receptor molecules (CD27, CD137, and SLAM-R) selectively involved in immune responses against infected B cells via specific T-B cell interactions.

Interleukin-2-Inducible T-Cell Kinase Deficiency Impairs Early Pulmonary Protection Against Mycobacterium tuberculosis Infection

Interleukin-2 (IL-2) inducible T-cell kinase (ITK) is a non-receptor tyrosine kinase highly expressed in T-cell lineages and regulates multiple aspects of T-cell development and function, mainly through its function downstream of the T-cell receptor. Itk deficiency can lead to CD4 lymphopenia and Epstein-Bar virus (EBV)-associated lymphoproliferation and recurrent pulmonary infections in humans. However, the role of the ITK signaling pathway in pulmonary responses in active tuberculosis due to Mtb infection is not known. We show here that human lungs with active tuberculosis exhibit altered T-cell receptor/ITK signaling and that Itk deficiency impaired early protection against Mtb in mice, accompanied by defective development of IL-17A-producing γδ T cells in the lungs. These findings have important implications of human genetics associated with susceptibility to Mtb due to altered immune responses and molecular signals modulating host immunity that controls Mtb activity. Enhancing ITK signaling pathways may be an alternative strategy to target Mtb infection, especially in cases with highly virulent strains in which IL-17A plays an essential protective role.

Th1 Cells Rolling on Selectins Trigger DAP12-Dependent Signals That Activate Integrin αLβ2

During inflammation, both neutrophils and effector T cells use selectins to roll and integrins to arrest in postcapillary venules. In both cell types, chemokines can transduce signals that convert integrin αLβ2 to a high-affinity conformation, which interacts with ICAM-1 to mediate arrest. In neutrophils, selectins also trigger an immunoreceptor-like signaling cascade that converts integrin αLβ2 to an intermediate-affinity conformation, which interacts with ICAM-1 to slow rolling. It is not known whether selectins induce similar signaling events in T cells. Ag engagement causes phosphorylation of ITAMs on the TCR; these motifs recruit kinases and adaptors that lead to the activation of αLβ2. We found that mouse Th1 cells rolling on P- or E-selectin triggered signals that promoted αLβ2-dependent slow rolling on ICAM-1 in vitro and in vivo. The selectin signaling cascade resembled that used by the TCR, except that unexpectedly, Th1 cells employed the ITAM-bearing protein DAP12, which was not known to be expressed in these cells. Importantly, outside-in signaling through ligand-occupied αLβ2 also required DAP12. Cooperative selectin and chemokine signaling in Th1 cells promoted αLβ2-dependent slow rolling and arrest in vitro and in vivo and migration into Ag-challenged tissues in vivo. Our findings reveal an important function for DAP12 in Th1 cells and a new mechanism to recruit effector T cells to sites of inflammation.

Structural basis for the activation of PLC-γ isozymes by phosphorylation and cancer-associated mutations

Direct activation of the human phospholipase C-γ isozymes (PLC-γ1, -γ2) by tyrosine phosphorylation is fundamental to the control of diverse biological processes, including chemotaxis, platelet aggregation, and adaptive immunity. In turn, aberrant activation of PLC-γ1 and PLC-γ2 is implicated in inflammation, autoimmunity, and cancer. Although structures of isolated domains from PLC-γ isozymes are available, these structures are insufficient to define how release of basal autoinhibition is coupled to phosphorylation-dependent enzyme activation. Here, we describe the first high-resolution structure of a full-length PLC-γ isozyme and use it to underpin a detailed model of their membrane-dependent regulation. Notably, an interlinked set of regulatory domains integrates basal autoinhibition, tyrosine kinase engagement, and additional scaffolding functions with the phosphorylation-dependent, allosteric control of phospholipase activation. The model also explains why mutant forms of the PLC-γ isozymes found in several cancers have a wide spectrum of activities, and highlights how these activities are tuned during disease.

Design, synthesis and structure-activity relationship of indolylindazoles as potent and selective covalent inhibitors of interleukin-2 inducible T-cell kinase (ITK)

Interleukin-2 inducible T-cell kinase (ITK), a member of the Tec family of tyrosine kinases, plays an important role in T cell signaling downstream of the T-cell receptor (TCR). Herein we report the discovery of a series of indolylindazole based covalent ITK inhibitors with nanomolar inhibitory potency against ITK, good kinase selectivity and potent inhibition of the phosphorylation of PLCγ1 and ERK1/2 in living cells. A computational study provided insight into the interactions between inhibitors and Phe437 at the ATP binding pocket of ITK, suggesting that both edge-to-face π-π interaction and the dihedral torsion angle contribute to inhibitors' potency. Compounds 43 and 55 stood out as selective covalent inhibitors with potent cellular activity, which could be used as chemical tools for further study of ITK functions.

Transient protein accumulation at the center of the T cell antigen-presenting cell interface drives efficient IL-2 secretion

Supramolecular signaling assemblies are of interest for their unique signaling properties. A µm scale signaling assembly, the central supramolecular signaling cluster (cSMAC), forms at the center of the interface of T cells activated by antigen-presenting cells. We have determined that it is composed of multiple complexes of a supramolecular volume of up to 0.5 µm3 and associated with extensive membrane undulations. To determine cSMAC function, we have systematically manipulated the localization of three adaptor proteins, LAT, SLP-76, and Grb2. cSMAC localization varied between the adaptors and was diminished upon blockade of the costimulatory receptor CD28 and deficiency of the signal amplifying kinase Itk. Reconstitution of cSMAC localization restored IL-2 secretion which is a key T cell effector function as dependent on reconstitution dynamics. Our data suggest that the cSMAC enhances early signaling by facilitating signaling interactions and attenuates signaling thereafter through sequestration of a more limited set of signaling intermediates.

Magnesium Restores Activity to Peripheral Blood Cells in a Patient With Functionally Impaired Interleukin-2-Inducible T Cell Kinase

Interleukin-2-inducible T cell kinase (ITK) is critical for T cell signaling and cytotoxicity, and control of Epstein-Barr virus (EBV). We identified a patient with a novel homozygous missense mutation (D540N) in a highly conserved residue in the kinase domain of ITK who presented with EBV-positive lymphomatoid granulomatosis. She was treated with interferon and chemotherapy and her disease went into remission; however, she has persistent elevation of EBV DNA in the blood, low CD4 T cells, low NK cells, and nearly absent iNKT cells. Molecular modeling predicts that the mutation increases the flexibility of the ITK kinase domain impairing phosphorylation of the protein. Stimulation of her T cells resulted in reduced phosphorylation of ITK, PLCγ, and PKC. The CD8 T cells were moderately impaired for cytotoxicity and degranulation. Importantly, addition of magnesium to her CD8 T cells in vitro restored cytotoxicity and degranulation to levels similar to controls. Supplemental magnesium in patients with mutations in another protein important for T cell signaling, MAGT1, was reported to restore EBV-specific cytotoxicity. Our findings highlight the critical role of ITK for T cell activation and suggest the potential for supplemental magnesium to treat patients with ITK deficiency.

T-cell expression of Bruton's tyrosine kinase promotes autoreactive T-cell activation and exacerbates aplastic anemia

The role of Bruton’s tyrosine kinase (BTK) in BCR signaling is well defined, and BTK is involved in B-cell development, differentiation, and malignancies. However, the expression of Btk in T cells and its role in T-cell function remain largely unknown. Here, we unexpectedly found high expression and activation of BTK in T cells. Deficiencies in BTK resulted in the impaired activation and proliferation of autoreactive T cells and ameliorated bone marrow failure (BMF) in aplastic anemia. Mechanistically, BTK is activated after TCR engagement and then phosphorylates PLCγ1, thus promoting T-cell activation. Treatment with acalabrutinib, a selective BTK inhibitor, decreased T-cell proliferation and ameliorated BMF in mice with aplastic anemia. Our results demonstrate an unexpected role of BTK in optimal T-cell activation and in the pathogenesis of autoimmune aplastic anemia, providing insights into the molecular regulation of T-cell activation and the pathogenesis of T-cell-mediated autoimmune disease.

A Precision B Cell-Targeted Therapeutic Approach to Autoimmunity Caused by Phosphatidylinositol 3-Kinase Pathway Dysregulation

The inositol lipid phosphatases PTEN and SHIP-1 play a crucial role in maintaining B cell anergy and are reduced in expression in B cells from systemic lupus erythematosus and type 1 diabetes patients, consequent to aberrant regulation by miRNA-7 and 155. With an eye toward eventual use in precision medicine therapeutic approaches in autoimmunity, we explored the ability of p110δ inhibition to compensate for PI3K pathway dysregulation in mouse models of autoimmunity. Low dosages of the p110δ inhibitor idelalisib, which spare the ability to mount an immune response to exogenous immunogens, are able to block the development of autoimmunity driven by compromised PI3K pathway regulation resultant from acutely induced B cell-targeted haploinsufficiency of PTEN and SHIP-1. These conditions do not block autoimmunity driven by B cell loss of the regulatory tyrosine phosphatase SHP-1. Finally, we show that B cells in NOD mice express reduced PTEN, and low-dosage p110δ inhibitor therapy blocks disease progression in this model of type 1 diabetes. These studies may aid in the development of precision treatments that act by enforcing PI3K pathway regulation in patients carrying specific risk alleles.

A negative role for the interleukin-2-inducible T-cell kinase (ITK) in human Foxp3+ TREG differentiation

The Tec kinases ITK (interleukin-2-inducible T-cell kinase) and RLK (resting lymphocyte kinase) are critical components of the proximal TCR/CD3 signal transduction machinery, and data in mice suggest that ITK negatively modulates regulatory T cell (T_REG) differentiation. However, whether Tec kinases modulate T_REG development and/or function in human T cells remains unknown. Using a novel self-delivery siRNA platform (sdRNA), we found that ITK knockdown in human primary naïve peripheral blood CD4 T cells increased Foxp3⁺ expression under both T_REG and T helper priming conditions. T_REG differentiated under ITK knockdown conditions exhibited enhanced expression of the co-inhibitory receptor PD-1 and were suppressive in a T cell proliferation assay. ITK knockdown decreased IL-17A production in T cells primed under Th17 conditions and promoted Th1 differentiation. Lastly, a dual ITK/RLK Tec kinase inhibitor did not induce Foxp3 in CD4 T cells, but conversely abrogated Foxp3 expression induced by ITK knockdown. Our data suggest that targeting ITK in human T cells may be an effective approach to boost T_REG in the context of autoimmune diseases, but concomitant inhibition of other Tec family kinases may negate this effect.

Discovery of 7H-pyrrolo[2,3-d]pyrimidine derivatives as selective covalent irreversible inhibitors of interleukin-2-inducible T-cell kinase (Itk)

Interleukin-2-inducible T-cell kinase (Itk) plays an important role in multiple signal transduction pathways in T and mast cells, and is a potential drug target for treating inflammatory diseases, autoimmune diseases, and T cell leukemia/lymphoma. Herein, we describe the discovery of a series of covalent Itk inhibitors based on the 7H-pyrrolo[2,3-d]pyrimidine scaffold. Placing an appropriate substitution group at a hydration site of the ATP binding pocket of Itk and using a saturated heterocyclic ring as a linker to the reactive group were crucial for selectivity. The optimized compound 9 showed potent activity against Itk, excellent selectivity for Itk over Btk and other structurally related kinases, inhibition of phospholipase C-γ1 (PLC-γ1) phosphorylation in cells, and anti-proliferative effects against multiple T leukemia/lymphoma cell lines. Compound 9 can serve as a valuable compound for further determination of functions of Itk.

Helicobacter pylori Deregulates T and B Cell Signaling to Trigger Immune Evasion

Helicobacter pylori is a prevalent human pathogen that successfully establishes chronic infection, which leads to clinically significant gastric diseases including chronic gastritis, peptic ulcer disease (PUD), and gastric cancer (GC). H. pylori is able to produce a persistent infection due in large part to its ability to hijack the host immune response. The host adaptive immune response is activated to strategically and specifically attack pathogens and normally clears them from the infected host. Since B and T lymphocytes are central mediators of adaptive immunity, in this chapter we review their development and the fundamental mechanisms regulating their activation in order to understand how some of the normal processes are subverted by H. pylori. In this review, we place particular emphasis on the CD4⁺ T cell responses, their subtypes, and regulatory mechanisms because of the expanding literature in this area related to H. pylori. T lymphocyte differentiation and function are finely orchestrated through a series of cell-cell interactions, which include immune checkpoint receptors. Among the immune checkpoint receptor family, there are some with inhibitory properties that are exploited by tumor cells to facilitate their immune evasion. Gastric epithelial cells (GECs), which act as antigen-presenting cells (APCs) in the gastric mucosa, are induced by H. pylori to express immune checkpoint receptors known to sway T lymphocyte function and thus circumvent effective T effector lymphocyte responses. This chapter reviews these and other mechanisms used by H. pylori to interfere with host immunity in order to persist.

Inherited Immunodeficiencies With High Predisposition to Epstein-Barr Virus-Driven Lymphoproliferative Diseases

Epstein–Barr Virus (EBV) is a gamma-herpes virus that infects 90% of humans without any symptoms in most cases, but has an oncogenic potential, especially in immunocompromised individuals. In the past 30 years, several primary immunodeficiencies (PIDs) associated with a high risk to develop EBV-associated lymphoproliferative disorders (LPDs), essentially consisting of virus-associated hemophagocytic syndrome, non-malignant and malignant B-cell LPDs including non-Hodgkin and Hodgkin’s types of B lymphomas have been characterized. Among them are SH2D1A (SAP), XIAP, ITK, MAGT1, CD27, CD70, CTPS1, RASGRP1, and CORO1A deficiencies. Penetrance of EBV infection ranges from 50 to 100% in those PIDs. Description of large cohorts and case reports has refined the specific phenotypes associated with these PIDs helping to the diagnosis. Specific pathways required for protective immunity to EBV have emerged from studies of these PIDs. SLAM-associated protein-dependent SLAM receptors and MAGT1-dependent NKG2D pathways are important for T and NK-cell cytotoxicity toward EBV-infected B-cells, while CD27–CD70 interactions are critical to drive the expansion of EBV-specific T-cells. CTPS1 and RASGRP1 deficiencies further strengthen that T-lymphocyte expansion is a key step in the immune response to EBV. These pathways appear to be also important for the anti-tumoral immune surveillance of abnormal B cells. Monogenic PIDs should be thus considered in case of any EBV-associated LPDs.

Comparative Proteomic Study of the Antiproliferative Activity of Frog Host-Defence Peptide Caerin 1.9 and Its Additive Effect with Caerin 1.1 on TC-1 Cells Transformed with HPV16 E6 and E7

Caerin is a family of peptides isolated from the glandular secretion of Australian tree frogs, the genus Litoria, and has been previously shown to have anticancer activity against several cancer cells. In this work, we used two host-defence peptides, caerin 1.1 and caerin 1.9, to investigate their ability to inhibit a murine derived TC-1 cell transformed with human papillomavirus 16 E6 and E7 growth in vitro. Caerin 1.9 inhibits TC-1 cell proliferation, although inhibition is more pronounced when applied in conjunction with caerin 1.1. To gain further insights into the antiproliferative mechanisms of caerin 1.9 and its additive effect with caerin 1.1, we used a proteomics strategy to quantitatively examine (i) the changes in the protein profiles of TC-1 cells and (ii) the excretory-secretory products of TC-1 cells following caerin peptides treatment. Caerin 1.9 treatment significantly altered the abundance of several immune-related proteins and related pathways, such as the Tec kinase and ILK signalling pathways, as well as the levels of proinflammatory cytokines and chemokines. In conclusion, caerin peptides inhibit TC-1 cell proliferation, associated with modification in signalling pathways that would change the tumour microenvironment which is normally immune suppressive.

Interleukin-2-Inducible T-Cell Kinase Deficiency-New Patients, New Insight?

Patients with primary immunodeficiency can be prone to severe Epstein–Barr virus (EBV) associated immune dysregulation. Individuals with mutations in the interleukin-2-inducible T-cell kinase (ITK) gene experience Hodgkin and non-Hodgkin lymphoma, EBV lymphoproliferative disease, hemophagocytic lymphohistiocytosis, and dysgammaglobulinemia. In this review, we give an update on further reported patients. We believe that current clinical data advocate early definitive treatment by hematopoietic stem cell transplantation, as transplant outcome in primary immunodeficiency disorders in general has gradually improved in recent years. Furthermore, we summarize experimental data in the murine model to provide further insight of pathophysiology in ITK deficiency.