InVivoMAb anti-human CD3

Rapid and uniform labeling of plasma membrane proteins is essential for high-resolution imaging of dynamic membrane topologies and intercellular communication in live mammalian cells. Existing strategies for labeling live cell membranes, such as fluorescent fusion proteins, enzyme-mediated tags, metabolic bioorthogonal labeling, and lipophilic dyes, face trade-offs in the requirement of genetic manipulation, the presence of non-uniform labeling, the need for extensive preparation times, and limited choices of fluorophores. Here, we present a streamlined protocol that leverages N-hydroxysuccinimide (NHS)-ester chemistry to achieve rapid (≤5 min), covalent conjugation of synthetic small-molecule dyes to surface-exposed primary amines, enabling pan-membrane-protein labeling. This workflow covers dye stock preparation, labeling for suspension and adherent cells, multiplex live-cell imaging, fusion protein co-staining (including insulin-triggered receptor endocytosis), 3D membrane visualization, and in vivo assays for visualizing membrane-derived material transfers between donor and recipient cells using a lymphoma T-cell mouse model. This high-density labeling approach is compatible with various cell types across diverse imaging platforms. Its speed, versatility, and stability make it a broadly applicable tool for studying plasma membrane dynamics and intercellular membrane trafficking. Key features • Rapid high-density membrane labeling with small-molecule fluorescent dyes. • Enables live-cell multiplexed imaging, amenable to primary cells and cells expressing fluorescent fusion proteins, and supports in vivo studies of membrane-associated cell-cell communications. • Compatible with various fluorescence imaging modalities.

A20, encoded by the TNFAIP3 gene, is a protein linked to Crohn's disease and celiac disease in humans. We now find that mice expressing point mutations in A20's M1-ubiquitin-binding zinc finger 7 (ZF7) motif spontaneously develop proximal enteritis that requires both luminal microbes and T cells. Cellular and transcriptomic profiling reveals expansion of Th17 cells and exuberant expression of IL-17A and IL-22 in intestinal lamina propria of A20ZF7 mice. While deletion of IL-17A from A20ZF7/ZF7 mice exacerbates enteritis, deletion of IL-22 abrogates intestinal epithelial cell hyperproliferation, barrier dysfunction, and alarmin expression. Colonization of adult germ-free mice with microbiota from adult WT specific pathogen-free mice drives duodenal IL-22 expression and duodenitis. A20ZF7/ZF7 Th17 cells autonomously express more RORγt and IL-22 after differentiation in vitro. ATAC sequencing identified an enhancer region upstream of the Il22 gene, and this enhancer demonstrated increased activating histone acetylation coupled with exaggerated Il22 transcription in A20ZF7/ZF7 T cells. Acute inhibition of RORγt normalized histone acetylation at this enhancer. Finally, CRISPR/Cas9-mediated ablation of A20ZF7 in human T cells increases RORγt expression and IL22 transcription. These studies link A20's M1-ubiquitin binding function with RORγt expression, expansion of Th17 cells, and epigenetic activation of IL-22-driven enteritis.

While human autopsy samples have provided insights into pulmonary immune mechanisms associated with severe viral respiratory diseases, the mechanisms that contribute to a clinically favorable resolution of viral respiratory infections remain unclear due to the lack of proper experimental systems. Using mice co-engrafted with a genetically matched human immune system and fetal lung xenograft (fLX), we mapped the immunological events defining successful resolution of SARS-CoV-2 infection in human lung tissues. Viral infection is rapidly cleared from fLX following a peak of viral replication, histopathological manifestations of lung disease and loss of AT2 program, as reported in human COVID-19 patients. Infection resolution is associated with the activation of a limited number of hematopoietic subsets, including inflammatory monocytes and CD3-expressing macrophage-like cells, which are highly enriched in viral RNA and dissipate upon infection resolution. Specific human fibroblast and endothelial subsets also elicit robust antiviral and monocyte chemotaxis signatures, respectively. Notably, systemic depletion of human CD4 + cells, but not CD3 + cells, significantly abrogates infection resolution in fLX and induces persistent infection, supporting the dominant role of peripheral CD4 + monocytes over T-cells in the resolution of acute SARS-CoV-2 infection. Collectively, our findings unravel a comprehensive picture of the immunological events defining effective resolution of SARS-CoV-2 infection in human lung tissues, revealing markedly divergent immunological trajectories between resolving and fatal COVID-19 cases.

Despite the efficacy of chimeric antigen receptor (CAR)-T cells in selected hematological malignancies, further improvement on CAR-T designs is still desirable. We hypothesize that modifying the CAR structure to enhance immunological synapse (IS) stabilization and CAR target-binding may be a feasible strategy. Here we show that the membrane protein, CD99, is critical for IS formation in T cells by mediating actin-microtubule interaction. CD99 deficiency abolishes IS formation and prevents effective in vivo T cell immunity. Mechanistically, CD99 interacts with microtubules and actins through the transmembrane and cytoplasmic domains, respectively, with which myosin and IQGAP1 interact. As such, incorporating the transmembrane and juxtamembrane domains of CD99 into the CAR structure enhances IS formation and improves the therapeutic efficacy of human CAR-T cells against lymphoma in immune-deficient mice. Our data thus suggest that CD99-mediated IS stabilization may help improve CAR design and efficacy.

Interleukin-2 (IL-2) regulates immune homeostasis by fine-tuning the balance between effector and regulatory T (Treg) cells. To identify regulators of IL-2 signaling, we performed genome-wide CRISPR-knockout screening in IL-2-dependent cells derived from a patient with adult T cell leukemia (ATL) and found enrichment of single guide RNAs targeting PRDM1, which encodes B lymphocyte-induced maturation protein 1 (BLIMP1). BLIMP1 inhibits IL-2 production by T cells; however, its role in IL-2 signaling remains unknown. Here, we show that overexpressing Prdm1 down-regulated IL-2 signaling, whereas Prdm1-deficiency enhanced IL-2 signaling in mouse CD4+ T cells and Treg cells with augmented IL-2 signaling in T cells from influenza-infected mice and during adoptive T cell transfer-induced colitis. Deleting PRDM1 in human CD4+ T cells and Treg cells also increased IL-2 signaling. Furthermore, CD4+ T cells from patients with ATL expressed less BLIMP1 and had enhanced IL-2 signaling, whereas overexpressing PRDM1 in ATL cells suppressed IL-2 signaling. Thus, BLIMP1 inhibits IL-2 signaling during normal and pathophysiological responses, suggesting that manipulating BLIMP1 could have therapeutic potential.

Signal transducer and activator of transcription 3 (STAT3) is a well-described transcription factor that mediates oxidative phosphorylation and glutamine uptake in bulk acute myeloid leukemia (AML) cells and leukemic stem cells (LSCs). STAT3 has also been shown to translocate to the mitochondria in AML cells, and phosphorylation at the serine 727 (pSTAT3 S727) residue has been shown to be especially important for STAT3's mitochondrial functions. We demonstrate that inhibition of STAT3 results in impaired mitochondrial function and decreased leukemia cell viability. We discovered a novel interaction of STAT3 with voltage-dependent anion channel 1 (VDAC1) in the mitochondria which provides a mechanism through which STAT3 modulates mitochondrial function and cell survival. Through VDAC1, STAT3 regulates calcium and oxidative phosphorylation in the mitochondria. STAT3 and VDAC1 inhibition also result in significantly reduced engraftment potential of LSCs, including primary samples resistant to venetoclax. These results implicate STAT3 as a therapeutic target in AML.

Glioblastoma remains a challenging indication for immunotherapy: the blood-brain barrier hampers accessibility for systemic treatments and the immunosuppressive microenvironment impedes immune attack. Intratumoral therapy with the proinflammatory cytokine interleukin-12 (IL-12) can revert immunosuppression but leakage into the circulation causes treatment-limiting toxicity. Here we engineer an IL-12Fc fusion cytokine with reduced binding to the neonatal Fc receptor FcRn. FcRn-silenced IL-12Fc avoids FcRn-mediated brain export, thus exhibits prolonged brain retention and reduced blood levels, which prevents toxicity. In murine glioblastoma, FcRn-silenced IL-12Fc induces more durable responses with negligible systemic cytokine exposure and boosts the efficacy of radio- and chemotherapy. It triggers anti-tumor responses independently of peripheral T cell influx or lymphopenia and leads to inflammatory polarization of the tumor microenvironment in patient-derived glioblastoma explants. FcRn-silencing of IL-12Fc may unlock the full potential of IL-12 for brain cancer therapy and could be further applied to containing the activity of other therapeutics targeting neurological diseases.

Dynamic protein distribution within and across the plasma membrane is pivotal in regulating cell communication. However, rapid, high-density labeling methods for multiplexed live imaging across diverse cell types remain scarce. Here, we demonstrate N-hydroxysuccinimide (NHS)-ester-based amine crosslinking of fluorescent dyes to uniformly label live mammalian cell surface proteins. Using model cell systems, we capture previously elusive membrane topology and cell-cell interactions. Live imaging shows transient membrane protein accumulation at cell-cell contacts and bidirectional migration patterns guided by membrane fibers in DC2.4 dendritic cells. Multiplexed superresolution imaging reveals the biogenesis of membrane tunneling nanotubes that facilitate intercellular transfer in DC2.4 cells, and caveolin 1-dependent endocytosis of insulin receptors in HEK293T cells. 3D superresolution imaging reveals membrane topology remodeling in response to stimulation, generation of microvesicles, and phagocytic activities in Jurkat T cells. Furthermore, NHS-labeling remains stable in vivo, enabling visualization of intercellular transfer among splenocytes using a T cell lymphoma mouse model.

Suppression of anticancer immune function is a key driver of tumorigenesis. Identifying molecular pathways that inhibit anticancer immunity is critical for developing novel immunotherapeutics. One such molecule that has recently been identified is the carbohydrate polysialic acid (polySia), whose expression is dramatically upregulated on both cancer cells and immune cells in breast cancer patient tissues. The role of polySia in the anticancer immune response, however, remains incompletely understood. In this study, we profile polySia expression on both healthy primary immune cells and on infiltrating immune cells in the tumour microenvironment (TME). These studies reveal polySia expression on multiple immune cell subsets in patient breast tumors. We find that stimulation of primary T-cells and macrophages in vitro induces a significant upregulation of polySia expression. We subsequently show that polySia is appended to a range of different carrier proteins within these immune cells. Finally, we find that selective removal of polySia can significantly potentiate killing of breast cancer cells by innate immune cells. These studies implicate polySia as a significant negative regulator of anticancer immunity.

Regulatory CD8 T cells (CD8 Treg) are responsible for the selective killing of self-reactive and pathogenic CD4 T cells. In autoimmune disease, CD8 Treg may accumulate in the peripheral blood but fail to control the expansion of pathogenic CD4 T cells that subsequently cause tissue destruction. This CD8 Treg dysfunction is due in part to the expression of inhibitory killer immunoglobulin-like receptors (KIR; KIR2DL isoforms [KIR2DL1, KIR2DL2, and KIR2DL3]); these molecules serve as autoimmune checkpoints and limit CD8 Treg activation.

Enhanced mortality, relapse rates, and increased prevalence of Clostridioides difficile infection (CDI) emphasize the need for better therapies and management approaches. Modulating host immune response to ameliorate CDI-associated immunopathology may provide new advantages to currently inadequate antibiotic therapies. Here, we identified progranulin (PGRN) as an important immune target upregulated in response to CDI. PGRN-deficient mice displayed dramatically higher mortality and aggravated epithelial barrier disruption compared with wild type (WT) mice after CDI despite equivalent levels of bacterial burden or toxin in the large intestine. Mechanistically, PGRN protection was mediated by IL-22 production from CD4+ T helper cells, as demonstrated by a decrease in colonic IL-22-producing CD4+ T helper cells in the intestine of PGRN-deficient mice upon CDI and a boost of IL-22-producing CD4+ T helper cells activated by PGRN ex vivo. Clinical evidence suggests that CDI patients had significantly higher serum levels of PGRN compared with healthy controls, which was significantly and positively correlated with IL-22. Our findings thus indicate a critical role for PGRN-promoted CD4+ T cell IL-22 production in shaping gut immunity and reestablishing the intestinal barrier during CDI. As an alternative to pathogen-targeted therapy, this study may provide a new host-directed therapeutic strategy to attenuate severe, refractory CDI.

CD38 has emerged as a potential therapeutic target for patients with systemic lupus erythematosus (SLE) but it is not known whether CD38 alters CD4+ T cell function. Using primary human T cells and CD38-sufficient and CD38-deficient Jurkat T cells, we demonstrate that CD38 shifts the T cell lipid profile of gangliosides from GM3 to GM2 by upregulating B4GALNT1 in a Sirtuin 1-dependent manner. Enhanced expression of GM2 causes ER stress by enhancing Ca2+ flux through the PLCγ1-IP3 pathway. Interestingly, correction of the calcium overload by an IP3 receptor inhibitor, but not by a store-operated calcium entry (SOCE) inhibitor, improves IL-2 production by CD4+ T cells in SLE. This study demonstrates that CD38 affects calcium homeostasis in CD4+ T cells by controlling cell membrane lipid composition that results in suppressed IL-2 production. CD38 inhibition with biologics or small drugs should be expected to benefit patients with SLE.

Acute myeloid leukemia (AML) is a devastating disease initiated and maintained by a rare subset of cells called leukemia stem cells (LSCs). LSCs are responsible for driving disease relapse, making the development of new therapeutic strategies to target LSCs urgently needed. The use of mass spectrometry-based metabolomics profiling has enabled the discovery of unique and targetable metabolic properties in LSCs. However, we do not have a comprehensive understanding of metabolite differences between LSCs and their normal counterparts, hematopoietic stem and progenitor cells (HSPCs). In this study, we used an unbiased mass spectrometry-based metabolomics analysis to define differences in metabolites between primary human LSCs and HSPCs, which revealed that LSCs have a distinct metabolome. Spermidine was the most enriched metabolite in LSCs compared with HSPCs. Pharmacological reduction of spermidine concentrations decreased LSC function but spared normal HSPCs. Polyamine depletion also decreased leukemic burden in patient-derived xenografts. Mechanistically, spermidine depletion induced LSC myeloid differentiation by decreasing eIF5A-dependent protein synthesis, resulting in reduced expression of a select subset of proteins. KAT7, a histone acetyltransferase, was one of the top candidates identified to be down-regulated by spermidine depletion. Overexpression of KAT7 partially rescued polyamine depletion-induced decreased colony-forming ability, demonstrating that loss of KAT7 is an essential part of the mechanism by which spermidine depletion targets AML clonogenic potential. Together, we identified and mechanistically dissected a metabolic vulnerability of LSCs that has the potential to be rapidly translated into clinical trials to improve outcomes for patients with AML.

Resistance to PD-1 blockade in onco-immunotherapy greatly limits its clinical application. T cell immunoglobulin and mucin domain containing-3 (Tim-3), a promising immune checkpoint target, is cleaved by ADAM10/17 to produce its soluble form (sTim-3) in humans, potentially becoming involved in anti-PD-1 resistance. Herein, serum sTim-3 upregulation was observed in non-small cell lung cancer (NSCLC) and various digestive tumors. Notably, serum sTim-3 is further upregulated in non-responding patients undergoing anti-PD-1 therapy for NSCLC and anti-PD-1-resistant cholangiocarcinoma patients. Furthermore, sTim-3 overexpression facilitates tumor progression and confers anti-PD-1 resistance in multiple tumor mouse models. Mechanistically, sTim-3 induces terminal T cell exhaustion and attenuates CD8+ T cell response to PD-1 blockade through carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM-1). Moreover, the ADAM10 inhibitor GI254023X, which blocks sTim-3 production, reduces tumor progression in Tim-3 humanized mice and reverses anti-PD-1 resistance in human tumor-infiltrating lymphocytes (TILs). Overall, human sTim-3 holds great predictive and therapeutic potential in onco-immunotherapy.

Cancer neoantigens have been shown to elicit cancer-specific T-cell responses and have garnered much attention for their roles in both spontaneous and therapeutically induced antitumor responses. Mass spectrometry (MS) profiling of tumor immunopeptidomes has been used, in part, to identify MHC-bound mutant neoantigen ligands. However, under standard conditions, MS-based detection of such rare but clinically relevant neoantigens is relatively insensitive, requiring 300 million cells or more. Here, to quantitatively define the minimum detectable amounts of therapeutically relevant MHC-I and MHC-II neoantigen peptides, we analyzed different dilutions of immunopeptidomes isolated from the well-characterized T3 mouse methylcholanthrene (MCA)-induced cell line by MS. Using either data-dependent acquisition or parallel reaction monitoring (PRM), we established the minimum amount of material required to detect the major T3 neoantigens in the presence or absence of high field asymmetric waveform ion mobility spectrometry (FAIMS). This analysis yielded a 14-fold enhancement of sensitivity in detecting the major T3 MHC-I neoantigen (mLama4) with FAIMS-PRM compared with PRM without FAIMS, allowing ex vivo detection of this neoantigen from an individual 100 mg T3 tumor. These findings were then extended to two other independent MCA-sarcoma lines (1956 and F244). This study demonstrates that FAIMS substantially increases the sensitivity of MS-based characterization of validated neoantigens from tumors.

Chimeric antigen receptor (CAR) T cell therapy has achieved remarkable clinical success in the treatment of hematological malignancies. However, producing these bespoke cancer-killing cells is a complicated ex vivo process involving leukapheresis, artificial T cell activation, and CAR construct introduction. The activation step requires the engagement of CD3/TCR and CD28 and is vital for T cell transfection and differentiation. Though antigen-presenting cells (APCs) facilitate activation in vivo, ex vivo activation relies on antibodies against CD3 and CD28 conjugated to magnetic beads. While effective, this artificial activation adds to the complexity of CAR T cell production as the beads must be removed prior to clinical implementation. To overcome this challenge, this work develops activating lipid nanoparticles (aLNPs) that mimic APCs to combine the activation of magnetic beads and the transfection capabilities of LNPs. It is shown that aLNPs enable one-step activation and transfection of primary human T cells with the resulting mRNA CAR T cells reducing tumor burden in a murine xenograft model, validating aLNPs as a promising platform for the rapid production of mRNA CAR T cells.

The gut microbiota is a critical factor in the regulation of host health, but the relationship between the differential resistance of hosts to pathogens and the interaction of gut microbes is not yet clear. Herein, we investigated the potential correlation between the gut microbiota of piglets and their disease resistance using single-cell transcriptomics, 16S amplicon sequencing, metagenomics, and untargeted metabolomics.

CD1d-restricted invariant NKT (iNKT) cells play a critical role in tumor immunity. However, the scarcity and limited persistence restricts their development and clinical application. Here, we demonstrated that iNKT cells could be efficiently expanded using modified cytokines combination from peripheral blood mononuclear cells. Introduction of IL-21 significantly increased the frequency of CD62L-positive memory-like iNKT cells. iNKT cells armoring with B7H3-targeting second generation CAR and IL-21 showed potent tumor cell killing activity. Moreover, co-expression of IL-21 promoted the activation of Stat3 signaling and reduced the expression of exhaustion markers in CAR-iNKT cells in vitro. Most importantly, IL-21-arming significantly prolonged B7H3 CAR-iNKT cell proliferation and survival in vivo, thus improving their therapeutic efficacy in mouse renal cancer xerograph models without observed cytokine-related adverse events. In summary, these results suggest that B7H3 CAR-iNKT armored with IL-21 is a promising therapeutic strategy for cancer treatment.