[Molecular profiling of myeloid/natural killer (NK) cell precursor acute leukemia].

Myeloid/natural killer (NK) cell precursor acute leukemia (MNKPL) has been described based on its clinical phenotype and immunophenotype, and proposed as a unique leukemia entity. However, due to its rarity and lack of defined distinctive molecular characteristics, there is currently no international consensus on this disease concept. We performed multi-omics analysis and revealed that MNKPL is distinct from acute myeloid leukemia, T-cell acute lymphoblastic leukemia, and mixed-phenotype acute leukemia. NOTCH1 and RUNX3 activation and BCL11B downregulation are hallmarks of MNKPL. Although NK cells have been classically considered to be lymphoid lineage-derived, our single-cell analysis using MNKPL cells suggested that NK cells and myeloid cells share common progenitor cells. Our retrospective case study uncovered that outcomes of MNKPL are unsatisfactory, even with hematopoietic cell transplantation. Multi-omics analysis and in vitro drug sensitivity assays revealed increased sensitivity to L-asparaginase and reduced levels of asparagine synthetase, supporting the clinically observed effectiveness of L-asparaginase.

Is the tumor cell side of the immunological synapse a polarized secretory domain?

The formation of a lytic immunological synapse (IS) is crucial for cytotoxic lymphocytes to accurately target and effectively eliminate malignant cells. While significant attention has been focused on the lymphocyte side of the IS, particularly its role as a secretory domain for lytic granules, the cancer cell side of the IS has remained relatively underexplored. Recent findings have revealed that cancer cells can rapidly polarize their actin cytoskeleton toward the IS upon interaction with natural killer (NK) cells, thereby evading NK cell-mediated cytotoxicity. In this Brief Research Report, we present preliminary findings suggesting that actin cytoskeleton remodeling at the cancer cell side of the IS is associated with the targeted secretion of small extracellular vesicles towards the interacting NK cell. We observed that multivesicular bodies (MVBs) preferentially accumulate in the synaptic region in cancer cells exhibiting synaptic accumulation of F-actin, compared to those lacking actin cytoskeleton remodeling. Extracellular immunofluorescence staining revealed increased surface exposure of CD63 at the cancer cell side of the IS, suggestive of the fusion of MVBs with the plasma membrane. This hypothesis was supported by a pH-sensitive probe demonstrating dynamic trafficking of CD63 to the extracellular region of the IS. Collectively, our data support the notion that cancer cells can engage in targeted secretion of extracellular vesicles in response to NK cell attack, underscoring the need for further research into the potential role of this process in facilitating cancer cell immune evasion.

Interleukin signaling in the regulation of natural killer cells biology in breast cancer.

In the field of breast cancer treatment, the immunotherapy involving natural killer (NK) cells is increasingly highlighting its distinct potential and significance. Members of the interleukin (IL) family play pivotal regulatory roles in the growth, differentiation, survival, and apoptosis of NK cells, and are central to their anti-tumor activity. These cytokines enhance the ability of NK cells to recognize and eliminate tumor cells by binding to specific receptors and activating downstream signaling pathways. Furthermore, interleukins do not function in isolation; the synergistic or antagonistic interactions between different interleukins can drive NK cells toward various functional pathways, ultimately leading to diverse outcomes for breast cancer patients. This paper reviews the intricate relationship between NK cells and interleukins, particularly within the breast cancer tumor microenvironment. Additionally, we summarize the latest clinical studies and advancements in NK cell therapy for breast cancer, along with the potential applications of interleukin signaling in these therapies. In conclusion, this article underscores the critical role of NK cells and interleukin signaling in breast cancer treatment, providing valuable insights and a significant reference for future research and clinical practice.

Epigenetic regulation in epithelial cells and innate lymphocyte responses to S. Typhi infection: insights into IFN-γ production and intestinal immunity.

Infection by Salmonella enterica serovar Typhi (S. Typhi), the cause of enteric fevers, is low in high-income countries but persistent in low- and middle-income countries, resulting in 65,400-187,700 deaths yearly. Drug resistance, including in the United States, exacerbates this issue. Evidence indicates that innate lymphocytes (INLs), such as natural killer (NK) cells, and unconventional T lymphocytes (e.g., Mucosal-associated invariant T (MAIT) cells and T-cell receptor gamma delta (TCR-γδ) cells) can impact the intestinal epithelial barrier, the primary site of exposure to S. Typhi. Moreover, INL production of IFN-γ is central in controlling S. Typhi infection. However, the impact of epithelial cells (EC) on the secretion of IFN-γ by INLs and the relationship between these events and epigenetic changes remains unknown. Epigenetic modifications in host cells are fundamental for their differentiation and function, including IFN-γ production. Herein, using a human organoid-derived polarized intestinal epithelial cell monolayer, we investigated the role of H3K4me3 and H3K27me3 epigenetic marks in intestinal immunity, focusing on the function of EC, NK, MAIT, and TCR-γδ cells in response to S. Typhi. This study builds on our previous findings that MAIT subsets exhibiting specific IFN-γ pattern signatures were associated with protection against typhoid fever and that S. Typhi infection regulates changes in chromatin marks that depend on individual cell subsets. Here, we show that cultures exposed to S. Typhi without EC exhibit a significant increase in NK and MAIT cells, and, to a lesser extent, TCR-γδ cells, expressing IFN-γ and H3K4me3 but not H3K27me3 marks, contrasting with cultures where EC is present. The influence of EC on INL H3K4me3 marks might be indirectly mediated through the modulation of IL-18 secretion via the Histone Deacetylase 6 gene during S. Typhi infection.

[A mechanistic study of radiotherapy on intratumoral NK cell infiltration augmentation by regulating the EZH2/CXCL10 pathway in hepatocellular carcinoma cells].

Objective: To investigate the effect and associated mechanism of tumor tissue-infiltrating NK cells after receiving radiotherapy for hepatocellular carcinoma (HCC). Methods: A HCC tumor-bearing mouse model was constructed using human hepatocellular carcinoma cell line (SK-Hep-1) and divided into four groups: control, radiotherapy, NK cell clearance, and NK clearance combined with radiotherapy. Tumor growth condition was simultaneously recorded. The NK cell ratio in peripheral blood and the NK cell intratumoral infiltration condition were detected by flow cytometry and immunohistochemistry. Lentiviral-constructed SK-Hep-1 cells was used to detect the effect of radiotherapy on the regulation of CXCL10 and NK cell chemotaxis following EZH2 overexpression. SK-Hep-1 cells were irradiated in vitro and in vivo. The expression levels of EZH2 and CXCL10 mRNA and protein in the two groups of cell lines and mouse tumor tissues were detected by reverse transcription polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA), western blotting (WB), and immunohistochemistry. The chemotaxis and blocking experiments were used to validate the chemotaxis effect of CXCL10 on NK cells. The independent sample t-test was used to compare the groups. P<0.05 was considered statistically significant. Results: The HCC tumor-bearing mouse model experiment showed that HCC tumor growth was most remarkable in the NK clearance combined with the radiotherapy group compared to the radiotherapy group (P<0.05). Compared with the control group, the number of NK cells in the peripheral blood of nude mice in the radiotherapy group was significantly reduced, while the NK cell intratumoral infiltration was significantly increased (P<0.05). Flow cytometry and immunohistochemistry showed in vitro and in vivo expressional alterations. The average expression levels of EZH2 mRNA and protein in hepatocellular carcinoma cell lines and tumor tissues were decreased in the radiotherapy group than the control group and mouse tumor tissues (P<0.05), while the mRNA and protein expression levels of CXCL10 increased (P<0.05). The cell supernatant following radiotherapy enhanced NK cell chemotaxis but inhibited CXCL10 neutralization. EZH2 overexpression validated that radiotherapy up-regulated CXCL10 mRNA and down-regulated protein expression levels in in vitro and in vivo experiments (P<0.05). The chemotactic effect on NK cells was significantly weakened with EZH2 overexpression following radiotherapy. Conclusion: NK cells, as immune effector cells, are directly involved in radiotherapy- activated anti-HCC immunity. Importantly, radiotherapy inhibits EZH2 expression in hepatocellular carcinoma, thereby upregulating CXCL10 expression and enhancing intratumoral NK cell invasion.

SARS-CoV-2 spike protein induces the cytokine release syndrome by stimulating T cells to produce more IL-2.

Introduction: Cytokine release syndrome (CRS) is one of the leading causes of mortality in patients with COVID-19 caused by the SARS-CoV-2 coronavirus. However, the mechanism of CRS induced by SARS-CoV-2 is vague. Methods: Using spike protein combined with IL-2, IFN-γ, and TNF-α to stimulate human peripheral blood mononuclear cells (PBMCs) to secrete CRS-related cytokines, the content of cytokines in the supernatant was detected, and the effects of NK, T, and monocytes were analyzed. Results: This study shows that dendritic cells loaded with spike protein of SARS-CoV-2 stimulate T cells to release much more interleukin-2 (IL-2,) which subsequently cooperates with spike protein to facilitate PBMCs to release IL-1ß, IL-6, and IL-8. These effects are achieved via IL-2 stimulation of NK cells to release tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ), as well as T cells to release IFN-γ Mechanistically, IFN-γ and TNF-α enhance the transcription of CD40, and the interaction of CD40 and its ligand stabilizes the membrane expression of toll-like receptor 4 (TLR4) that serves as a receptor of spike protein on the surface of monocytes. As a result, there is a constant interaction between spike protein and TLR4, leading to continuous activation of nuclear factor-κ-gene binding (NF-κB). Furthermore, TNF-α also activates NF-κB signaling in monocytes, which further cooperates with IFN-γ and spike protein to modulate NF-κB-dependent transcription of CRS-related inflammatory cytokines. Discussion: Targeting TNF-α/IFN-γ in combination with TLR4 may represent a promising therapeutic approach for alleviating CRS in individuals with COVID-19.

The activating receptor NKG2D is an anti-fungal pattern recognition receptor.

NKG2D is a central activating receptor involved in target recognition and killing by Natural Killer and CD8+ T cells. The known role of NKG2D is to recognize a family of self-induced stress ligands that are upregulated on stressed cells such as cancerous or virally infected cells. Fungal pathogens are a major threat to human health, infecting more than a billion patients yearly and becoming more common and drug resistant. Here we show that NKG2D plays a critical role in the immune response against fungal infections. NKG2D can recognize fungal pathogens from most major families including Candida, Cryptococcus and Aspergillus species, and mice lacking NKG2D are extremely sensitive to fungal infections in models of both invasive and mucosal infections, making NKG2D an anti-fungal pattern recognition receptor.

Increased peritoneal TGF-ß1 is associated with ascites-induced NK-cell dysfunction and reduced survival in high-grade epithelial ovarian cancer.

Natural killer (NK) cell therapy represents an attractive immunotherapy approach against recurrent epithelial ovarian cancer (EOC), as EOC is sensitive to NK cell-mediated cytotoxicity. However, NK cell antitumor activity is dampened by suppressive factors in EOC patient ascites. Here, we integrated functional assays, soluble factor analysis, high-dimensional flow cytometry cellular component data and clinical parameters of advanced EOC patients to study the mechanisms of ascites-induced inhibition of NK cells. Using a suppression assay, we found that ascites from EOC patients strongly inhibits peripheral blood-derived NK cells and CD34+ progenitor-derived NK cells, albeit the latter were more resistant. Interestingly, we found that higher ascites-induced NK cell inhibition correlated with reduced progression-free and overall survival in EOC patients. Furthermore, we identified transforming growth factor (TGF)-ß1 to correlate with ascites-induced NK cell dysfunction and reduced patient survival. In functional assays, we showed that proliferation and anti-tumor reactivity of CD34+ progenitor-derived NK cells are significantly affected by TGF-ß1 exposure. Moreover, inhibition of TGF-ß1 signaling with galunisertib partly restored NK cell functionality in some donors. For the cellular components, we showed that the secretome is associated with a different composition of CD45+ cells between ascites of EOC and benign reference samples with higher proportions of macrophages in the EOC patient samples. Furthermore, we revealed that higher TGF-ß1 levels are associated with the presence of M2-like macrophages, B cell populations and T-regulatory cells in EOC patient ascites. These findings reveal that targeting TGF-ß1 signaling could increase NK cell immune responses in high-grade EOC patients.

Integrated multi-omics profiling reveals the ZZZ3/CD70 axis is a super-enhancer-driven regulator of diffuse large B-cell lymphoma cell-natural killer cell interactions.

Tumor immune microenvironment is crucial for diffuse large B-cell lymphoma (DLBCL) development. However, the mechanisms by which super-enhancers (SEs) regulate the interactions between DLBCL cells and tumor-infiltrating immune cells remains largely unknown. This study aimed to investigate the role of SE-controlled genes in regulating the interactions between DLBCL cells and tumor-infiltrating immune cells. Single-cell RNA-seq, bulk RNA-seq and H3K27ac ChIP-seq data were downloaded from the Heidelberg Open Research Data database and Gene Expression Omnibus database. HOMER algorithm and Seurat package in R were used for bioinformatics analysis. Cell proliferation and lactate dehydrogenase (LDH) release was detected by MTS and LDH release assays, respectively. Interaction between B cell cluster and CD8+ T cell and NK cell cluster was most obviously enhanced in DLBCL, with CD70-CD27, MIF-CD74/CXCR2 complex, MIF-CD74/CD44 complex and CCL3-CCR5 interactions were significantly increased. NK cell sub-cluster showed the strongest interaction with B cell cluster. ZZZ3 upregulated the transcription of CD70 by binding to its SE. Silencing CD70 in DOHH2 cells significantly promoted the proliferation of co-cultured NK92 cells and LDH release from DOHH2 cells, which was counteracted by ZZZ3 overexpression in DOHH2 cells. CD70 silencing combined with PD-L1 blockade promoted LDH release from DOHH2 cells co-cultured with NK92 cells. In conclusion, DLBCL cells inhibited the proliferation and killing of infiltrating NK cells by regulating ZZZ3/CD70 axis. Targeting ZZZ3/CD70 axis combined with PD-L1 blockade is expected to be a promising strategy for DLBCL treatment.

Harnessing B7-H6 for Anticancer Immunotherapy: Expression, Pathways, and Therapeutic Strategies.

Cancer therapies have evolved from traditional chemotherapy to more precise molecular-targeted immunotherapies, which have been associated with improved side effects and outcomes. These modern strategies rely on cancer-specific biomarkers that differentiate malignant from normal cells. The B7 family of immune checkpoint molecules is crucial for cancer immune evasion and a prime therapeutic target. B7-H6, a recently identified member of the B7 family, has emerged as a promising therapeutic target. Unlike other B7 proteins, B7-H6 is not expressed in healthy tissues but is upregulated in several cancers. It binds to NKp30, activating natural killer (NK) cells and triggering immune responses against cancer cells. This review explores the expression of B7-H6 in different cancers, the factors that regulate its expression, and its intrinsic and extrinsic pathways. Additionally, we discuss potential anticancer therapies targeting B7-H6, highlighting its significance in advancing precision medicine. Understanding the role of B7-H6 in cancer immunity may inform the development of appropriate therapies that exploit its cancer-specific expression.

Immunometabolic changes and potential biomarkers in CFS peripheral immune cells revealed by single-cell RNA sequencing.

The pathogenesis of Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) remains unclear, though increasing evidence suggests inflammatory processes play key roles. In this study, single-cell RNA sequencing (scRNA-seq) of peripheral blood mononuclear cells (PBMCs) was used to decipher the immunometabolic profile in 4 ME/CFS patients and 4 heathy controls. We analyzed changes in the composition of major PBMC subpopulations and observed an increased frequency of total T cells and a significant reduction in NKs, monocytes, cDCs and pDCs. Further investigation revealed even more complex changes in the proportions of cell subpopulations within each subpopulation. Gene expression patterns revealed upregulated transcription factors related to immune regulation, as well as genes associated with viral infections and neurodegenerative diseases.CD4+ and CD8+ T cells in ME/CFS patients show different differentiation states and altered trajectories, indicating a possible suppression of differentiation. Memory B cells in ME/CFS patients are found early in the pseudotime, indicating a unique subtype specific to ME/CFS, with increased differentiation to plasma cells suggesting B cell overactivity. NK cells in ME/CFS patients exhibit reduced cytotoxicity and impaired responses, with reduced expression of perforin and CD107a upon stimulation. Pseudotime analysis showed abnormal development of adaptive immune cells and an enhanced cell-cell communication network converging on monocytes in particular. Our analysis also identified the estrogen-related receptor alpha (ESRRA)-APP-CD74 signaling pathway as a potential biomarker for ME/CFS in peripheral blood. In addition, data from the GSE214284 database confirmed higher ESRRA expression in the monocyte cell types of male ME/CFS patients. These results suggest a link between immune and neurological symptoms. The results support a disease model of immune dysfunction ranging from autoimmunity to immunodeficiency and point to amyloidotic neurodegenerative signaling pathways in the pathogenesis of ME/CFS. While the study provides important insights, limitations include the modest sample size and the evaluation of peripheral blood only. These findings highlight potential targets for diagnostic biomarkers and therapeutic interventions. Further research is needed to validate these biomarkers and explore their clinical applications in managing ME/CFS.

Immunomodulatory effects of immune cell-derived extracellular vesicles in melanoma.

Melanoma, recognized as one of the most immunogenic malignancies in humans, holds paramount significance in the realm of immunotherapy. However, the emergence of drug resistance and the occurrence of adverse drug reactions underscore the pressing need to explore increasingly personalized immunotherapeutic modalities. Extracellular Vesicles (EVs), pivotal derivatives of immune cells, assume pivotal roles by encapsulating proteins, lipids, and nucleic acids within bilayer lipid structures, thereby facilitating targeted delivery to other immune cells. This orchestrated process orchestrates critical functions including antigen presentation, immune modulation, and the induction of apoptosis in tumor cells. A burgeoning body of evidence underscores the vast therapeutic potential of EVs in melanoma treatment. This comprehensive review aims to delineate the roles of EVs derived from immune cells such as dendritic cells, natural killer cells, macrophages, and T cells in the context of melanoma patients, thereby furnishing invaluable insights for the future direction of melanoma immunotherapy.

Peripheral NK cell phenotypic alteration and dysfunctional state post hepatitis B subviral particles stimulation in CHB patients: evading immune surveillance.

Background: The relationship between chronic hepatitis B (CHB) infection and natural killer (NK) cell dysfunction is well-established, but the specific role of HBV viral antigens in driving NK cell impairment in patients with CHB remains unclear. This study investigates the modulatory effects of hepatitis B virus subviral particles (HBVsvp, a representative model for HBsAg) on the phenotypic regulation (activating and inhibitory receptors), cytokine production and cytotoxic potential of peripheral blood mononuclear cell-derived natural killer cells (PBMCs-derived NK cell), which contributes to NK cell dysfunction in CHB infection, potentially serving as an effective HBV immune evasion strategy by the virus. Methods: NK cells were isolated from peripheral blood of patients with CHB (n=5) and healthy individuals (n=5), stimulated with HBVsvp. Subsequent flow cytometric characterization involved assessing changes in activating (NKp46 and NKG2D) and inhibitory (CD94) receptors expression, quantifying TNF-α and IFN- γ cytokine secretion, and evaluating the cytotoxic response against HepG2.2.15 cells with subsequent HBVsvp quantification. Results: In CHB patients, in vitro exposure of PBMCs-derived NK cell with HBVsvp (represent HBsAg model) significantly reduced NK cell-activating receptors expression (P = 0.022), increased expression of CD94 + NK cells (p = 0.029), accompanied with a reduced TNF-α - IFN-γ cytokine levels, and impaired cytotoxic capacity (evidenced by increased cell proliferation and elevated HBVsvp levels in co-cultures with HepG2.2.15 cells in a time-dependent), relative to healthy donors. Conclusion: These findings suggest that HBVsvp may induce dysfunctional NK cell responses characterized by phenotypic imbalance with subsequent reduction in cytokine and cytotoxic levels, indicating HBVsvp immunosuppressive effect that compromises antiviral defense in CHB patients. These data enhance our understanding of NK cell interactions with HBsAg and highlight the potential for targeting CD94 inhibitory receptors to restore NK cell function as an immunotherapeutic approach. Further clinical research is needed to validate these observations and establish their utility as reliable biomarkers.

Exhausted signature and regulatory network of NK cells in myasthenia gravis.

Introduction: NK cells are dysfunctional in myasthenia gravis (MG), but the mechanism is unclear. This study aims to measure associations and underlying mechanisms between the NK cells and the development of MG. Methods: Twenty healthy controls (HCs) and 53 MG patients who did not receive glucocorticoids and immunosuppressants were collected. According to the Myasthenia Gravis Foundation of America (MGFA) classification, MG patients were categorized into MGFA I group (n = 18) and MGFA II-IV group (n = 35). Flow cytometry, cell sorting, ELISA, mRNA-sequencing, RT-qPCR, western blot, and cell culture experiments were performed to evaluate the regulatory mechanism of exhausted NK cells. Results: Peripheral NK cells in MGFA II-IV patients exhibit exhausted phenotypes than HCs, marked by the dramatic loss of total NK cells, CD56dimCD16- NK cells, elevated PD1 expression, reduced NKG2D expression, impaired cytotoxic activity (perforin, granzyme B, CD107a) and cytokine secretion (IFN-γ). Plasma IL-6 and IL-21 are elevated in MG patients and mainly derived from the aberrant expansion of monocytes and Tfh cells, respectively. IL-6/IL-21 cooperatively induced NK-cell exhausted signature via upregulating SOCS2 and inhibiting the phosphorylation of STAT5. SOCS2 siRNA and IL-2 supplement attenuated the IL-6/IL-21-mediated alteration of NK-cell phenotypes and function. Discussion: Inhibition of IL-6/IL-21/SOCS2/STAT5 pathway and recovery of NK-cell ability to inhibit autoimmunity may be a new direction in the treatment of MG.

The Role of NK and T Cells in Endometriosis.

Endometriosis, a debilitating condition, affects one in ten women of reproductive age. Its pathophysiology remains unclear, though deficiencies in immune surveillance are thought to create an environment conducive to the evasion of ectopic endometrial cells from the immune system. Our research explores the immunological impact of endometriosis both locally and systemically, emphasizing natural killer (NK) and T cell subpopulations. We incorporated 62 female patients who underwent laparoscopic surgery; of those, 47 had endometriosis, and 15 were controls. We collected peritoneal fluid (PF) and peripheral blood (PB) samples which were tagged with monoclonal antibodies and subsequently scrutinized using flow cytometry. Our findings revealed significant differences in immunological profiles based on demographic factors and symptomatology. In the endometriosis cohort, there was an increase in PB CD56HiCD16dim and PF CD8+ CD56dimCD16Hi NK cells. CD16+ CD4 T cell levels were significantly lower in the PB of endometriosis patients who smoke. Individuals with more severe disease displayed significantly higher levels of PB CD16+ CD8 T cells, which also increased in those with non-menstrual pelvic pain. Dysmenorrhea severity correlated with a progressive increase in PF CD8+ CD56dimCD16Hi NK cells. These variations in specific lymphocyte subsets, namely, within NK and T cells, suggest potential immunological mechanisms in the evolution and clinical presentation of endometriosis.

The basic biology of NK cells and its application in tumor immunotherapy.

Natural Killer (NK) cells play a crucial role as effector cells within the tumor immune microenvironment, capable of identifying and eliminating tumor cells through the expression of diverse activating and inhibitory receptors that recognize tumor-related ligands. Therefore, harnessing NK cells for therapeutic purposes represents a significant adjunct to T cell-based tumor immunotherapy strategies. Presently, NK cell-based tumor immunotherapy strategies encompass various approaches, including adoptive NK cell therapy, cytokine therapy, antibody-based NK cell therapy (enhancing ADCC mediated by NK cells, NK cell engagers, immune checkpoint blockade therapy) and the utilization of nanoparticles and small molecules to modulate NK cell anti-tumor functionality. This article presents a comprehensive overview of the latest advances in NK cell-based anti-tumor immunotherapy, with the aim of offering insights and methodologies for the clinical treatment of cancer patients.

Bispecific killer cell engagers employing species cross-reactive NKG2D binders redirect human and murine lymphocytes to ErbB2/HER2-positive malignancies.

NKG2D is an activating receptor expressed by natural killer (NK) cells and other cytotoxic lymphocytes that plays a pivotal role in the elimination of neoplastic cells through recognition of different stress-induced cell surface ligands (NKG2DL). To employ this mechanism for cancer immunotherapy, we generated NKG2D-engaging bispecific antibodies that selectively redirect immune effector cells to cancer cells expressing the tumor-associated antigen ErbB2 (HER2). NKG2D-specific single chain fragment variable (scFv) antibodies cross-reactive toward the human and murine receptors were derived by consecutive immunization of chicken with the human and murine antigens, followed by stringent screening of a yeast surface display immune library. Four distinct species cross-reactive (sc) scFv domains were selected, and reformatted into a bispecific engager format by linking them via an IgG4 Fc domain to a second scFv fragment specific for ErbB2. The resulting molecules (termed scNKAB-ErbB2) were expressed as disulfide-linked homodimers, and demonstrated efficient binding to ErbB2-positive cancer cells as well as NKG2D-expressing primary human and murine lymphocytes, and NK-92 cells engineered with chimeric antigen receptors derived from human and murine NKG2D (termed hNKAR and mNKAR). Two of the scNKAB-ErbB2 molecules were found to compete with the natural NKG2D ligand MICA, while the other two engagers interacted with an epitope outside of the ligand binding site. Nevertheless, all four tested scNKAB-ErbB2 antibodies were similarly effective in redirecting the cytotoxic activity of primary human and murine lymphocytes as well as hNKAR-NK-92 and mNKAR-NK-92 cells to ErbB2-expressing targets, suggesting that further development of these species cross-reactive engager molecules for cancer immunotherapy is warranted.

MASTER-NAADP: a membrane permeable precursor of the Ca2+ mobilizing second messenger NAADP.

Upon stimulation of membrane receptors, nicotinic acid adenine dinucleotide phosphate (NAADP) is formed as second messenger within seconds and evokes Ca2+ signaling in many different cell types. Here, to directly stimulate NAADP signaling, MASTER-NAADP, a Membrane permeAble, STabilized, bio-rEversibly pRotected precursor of NAADP is synthesized and release of its active NAADP mimetic, benzoic acid C-nucleoside, 2'-phospho-3'F-adenosine-diphosphate, by esterase digestion is confirmed. In the presence of NAADP receptor HN1L/JPT2 (hematological and neurological expressed 1-like protein, HN1L, also known as Jupiter microtubule-associated homolog 2, JPT2), this active NAADP mimetic releases Ca2+ and increases the open probability of type 1 ryanodine receptor. When added to intact cells, MASTER-NAADP initially evokes single local Ca2+ signals of low amplitude. Subsequently, also global Ca2+ signaling is observed in T cells, natural killer cells, and Neuro2A cells. In contrast, control compound MASTER-NADP does not stimulate Ca2+ signaling. Likewise, in cells devoid of HN1L/JPT2, MASTER-NAADP does not affect Ca2+ signaling, confirming that the product released from MASTER-NAADP is a bona fide NAADP mimetic.

Maintaining the Balance: Regulation of NK Cell Activity.

Natural Killer (NK) cells, integral components of the innate immune system, play a crucial role in the protection against intracellular threats. Their cytotoxic power requires that activation is tightly controlled, and in this, they take a unique position within the immune system. Rather than depending on the engagement of a single activating receptor, their activation involves a delicate balance between inhibitory and activating signals mediated through an array of surface molecules. Only when this cumulative balance surpasses a specific threshold do NK cells initiate their activity. Remarkably, the activation threshold of NK cells remains robust even when cells express vastly different repertoires of inhibitory and activating receptors. These threshold values seem to be influenced by NK cell interactions with their environment during development and after release from the bone marrow. Understanding how NK cells integrate this intricate pattern of stimuli is an ongoing area of research, particularly relevant for cellular therapies seeking to harness the anti-cancer potential of these cells by modifying surface receptor expression. In this review, we will explore some of the current dogmas regarding NK cell activation and discuss recent literature addressing advances in our understanding of this field.

Large Extracellular Vesicles Derived from Natural Killer Cells Affect the Functions of Monocytes.

Communication between natural killer cells (NK cells) and monocytes/macrophages may play an important role in immunomodulation and regulation of inflammatory processes. The aim of this research was to investigate the impact of NK cell-derived large extracellular vesicles on monocyte function because this field is understudied. We studied how NK-cell derived large extracellular vesicles impact on THP-1 cells characteristics after coculturing: phenotype, functions were observed with flow cytometry. In this study, we demonstrated the ability of large extracellular vesicles produced by NK cells to integrate into the membranes of THP-1 cells and influence the viability, phenotype, and functional characteristics of the cells. The results obtained demonstrate the ability of large extracellular vesicles to act as an additional component in the immunomodulatory activity of NK cells in relation to monocytes.