[Flow cytometry analysis of normal range of natural killer cells and their subsets in peripheral blood of healthy Chinese adults].

OBJECTIVE: To study the distribution characteristics of natural killer (NK) cells and their subsets in normal peripheral blood in China, and to explore their normal value and significance. METHODS: In this study, peripheral blood was collected from 200 healthy adults. Their age range was 18-87 years. All the subjects were divided into 6 age groups: 18-30, 31-40, 41-50, 51-60, 61-70, and 71-87 years. With CD16, CD56, CD4, CD19, as surface markers, fluid cytology detection techniques were used to detect NK cells and the relative and absolute counts. SPSS 27.0 was used for systematic analysis of the data, and the measurement data were expressed as mean±standard deviations. A t test, variance analysis or rank sum test were performed to compare the differences between the age groups and the sex groups. The significance level was set at α=0.05, and P < 0.05 was considered statistically significant. RESULTS: The range of NK B cells in the 200 healthy adult subjects was (0.46±0.24)×106/L, that of CD3-CD56+NK cells was (13.14±7.56)×106/L, that of CD56dimCD16+NK cells was (5.23±3.12)×106/L, that of CD56brightNK cells was (85.61±7.40)×106/L, and that of NK T cells was (4.16±3.34)×106/L. There were no statistically significant differences in CD3-CD56+NK cells and NK T cells with respect to age (P= 0.417, P=0.217). However, there was a decreasing trend in the number of NK B cells and CD56dimCD16+NK cells with increasing age (r=0.234, P < 0.001; r=0.099, P < 0.001), particularly after the age of 50. Conversely, CD56brightNK cells showed an increasing trend with age (r=0.143, P < 0.001). CONCLUSION: The detection of NK cells and their subsets has significant reference value for the diagnosis, treatment, and prognosis of autoimmune diseases, infectious diseases, and tumors. This study provides a preliminary reference range for clinical detection of NK cell subsets, but further research with a larger sample size and multi-center trials are needed to confirm these findings.

Efficient generation of human NOTCH ligand-expressing haemogenic endothelial cells as infrastructure for in vitro haematopoiesis and lymphopoiesis.

Arterial endothelial cells (AECs) are the founder cells for intraembryonic haematopoiesis. Here, we report a method for the efficient generation of human haemogenic DLL4+ AECs from pluripotent stem cells (PSC). Time-series single-cell RNA-sequencing reveals the dynamic evolution of haematopoiesis and lymphopoiesis, generating cell types with counterparts present in early human embryos, including stages marked by the pre-haematopoietic stem cell genes MECOM/EVI1, MLLT3 and SPINK2. DLL4+ AECs robustly support lymphoid differentiation, without the requirement for exogenous NOTCH ligands. Using this system, we find IL7 acts as a morphogenic factor determining the fate choice between the T and innate lymphoid lineages and also plays a role in regulating the relative expression level of RAG1. Moreover, we document a developmental pathway by which human RAG1+ lymphoid precursors give rise to the natural killer cell lineage. Our study describes an efficient method for producing lymphoid progenitors, providing insights into their endothelial and haematopoietic ontogeny, and establishing a platform to investigate the development of the human blood system.

Protocol for isolating high-purity natural killer cells from peripheral blood of septic patients using magnetic cell separation.

In human sepsis, myelocytosis and concomitant lymphopenia complicate the study of peripheral blood natural killer (NK) cells. Here, we present a protocol for isolating NK cells from peripheral blood of septic patients using magnetic cell separation. We describe steps for the depletion of non-NK cells and NK cell enrichment. We then detail procedures for comparing the results from this protocol to results obtained through the isolation procedures using two commercially available kits for NK cell isolation. For complete details on the use and execution of this protocol, please refer to Coulibaly et al.1.

Comparison of Natural Killer Cells Differentiated from Various Pluripotent Stem Cells.

Allogeneic natural killer (NK) cell therapy has been effective in treating cancer. Many studies have tested NK cell therapy using human pluripotent stem cells (hPSCs). However, the impacts of the origin of PSC-NK cells on competence are unclear. In this study, several types of hPSCs, including human-induced PSCs (hiPSCs) generated from CD34+, CD3-CD56+, and CD56- cells in umbilical cord blood (UCB), three lines of human embryonic stem cells (hESCs, ES-1. ES-2 and ES-3) and MHC I knockout (B2M-KO)-ESCs were used to differentiate into NK cells and their capacities were analyzed. All PSC types could differentiate into NK cells. Among the iPSC-derived NK cells (iPSC-NKs) and ESC-derived NK cells (ES-NKs), 34+ iPSCs and ES-3 had a higher growth rate and cytotoxicity, respectively, ES-3 also showed better efficacy than 34+ iPSCs. B2M-KO was similar to the wild type. These results suggest that the screening for differentiation of PSCs into NK cells prior to selecting the PSC lines for the development of NK cell immunotherapy is an essential process for universal allotransplantation, including the chimeric antigen receptor (CAR).

Use of a platform with lens-free shadow imaging technology to monitor natural killer cell activity.

Natural killer (NK) cells are a crucial component of the innate immune system. This study introduces Cellytics NK, a novel platform for rapid and precise measurement of NK cell activity. This platform combines an NK-specific activation stimulator cocktail (ASC) and lens-free shadow imaging technology (LSIT), using optoelectronic components. LSIT captures digital hologram images of resting and ASC-activated NK cells, while an algorithm evaluates cell size and cytoplasmic complexity using shadow parameters. The combined shadow parameter derived from the peak-to-peak distance and width standard deviation rapidly distinguishes active NK cells from inactive NK cells at the single-cell level within 30 s. Here, the feasibility of the system was demonstrated by assessing NK cells from healthy donors and immunocompromised cancer patients, demonstrating a significant difference in the innate immunity index (I3). Cancer patients showed a lower I3 value (161%) than healthy donors (326%). I3 was strongly correlated with NK cell activity measured using various markers such as interferon-gamma, tumor necrosis factor-alpha, perforin, granzyme B, and CD107a. This technology holds promise for advancing immune functional assays, offering rapid and accurate on-site analysis of NK cells, a crucial innate immune cell, with its compact and cost-effective optoelectronic setup, especially in the post-COVID-19 era.

Pretreatment with IL-15 and IL-18 rescues natural killer cells from granzyme B-mediated apoptosis after cryopreservation.

Human natural killer (NK) cell-based therapies are under assessment for treating various cancers, but cryopreservation reduces both the recovery and function of NK cells, thereby limiting their therapeutic feasibility. Using cryopreservation protocols optimized for T cells, here we find that ~75% of NK cells die within 24 h post-thaw, with the remaining cells displaying reduced cytotoxicity. Using CRISPR-Cas9 gene editing and confocal microscopy, we find that cryopreserved NK cells largely die via apoptosis initiated by leakage of granzyme B from cytotoxic vesicles. Pretreatment of NK cells with a combination of Interleukins-15 (IL-15) and IL-18 prior to cryopreservation improves NK cell recovery to ~90-100% and enables equal tumour control in a xenograft model of disseminated Raji cell lymphoma compared to non-cryopreserved NK cells. The mechanism of IL-15 and IL-18-induced protection incorporates two mechanisms: a transient reduction in intracellular granzyme B levels via degranulation, and the induction of antiapoptotic genes.

cellPLATO - an unsupervised method for identifying cell behaviour in heterogeneous cell trajectory data.

Advances in imaging, segmentation and tracking have led to the routine generation of large and complex microscopy datasets. New tools are required to process this 'phenomics' type data. Here, we present 'Cell PLasticity Analysis Tool' (cellPLATO), a Python-based analysis software designed for measurement and classification of cell behaviours based on clustering features of cell morphology and motility. Used after segmentation and tracking, the tool extracts features from each cell per timepoint, using them to segregate cells into dimensionally reduced behavioural subtypes. Resultant cell tracks describe a 'behavioural ID' at each timepoint, and similarity analysis allows the grouping of behavioural sequences into discrete trajectories with assigned IDs. Here, we use cellPLATO to investigate the role of IL-15 in modulating human natural killer (NK) cell migration on ICAM-1 or VCAM-1. We find eight behavioural subsets of NK cells based on their shape and migration dynamics between single timepoints, and four trajectories based on sequences of these behaviours over time. Therefore, by using cellPLATO, we show that IL-15 increases plasticity between cell migration behaviours and that different integrin ligands induce different forms of NK cell migration.

Beyond CAR T cells: exploring alternative cell sources for CAR-like cellular therapies.

Chimeric antigen receptor (CAR)-T cell therapy has led to remarkable clinical outcomes in the treatment of hematological malignancies. However, challenges remain, such as limited infiltration into solid tumors, inadequate persistence, systemic toxicities, and manufacturing insufficiencies. The use of alternative cell sources for CAR-based therapies, such as natural killer cells (NK), macrophages (MΦ), invariant Natural Killer T (iNKT) cells, γδT cells, neutrophils, and induced pluripotent stem cells (iPSC), has emerged as a promising avenue. By harnessing these cells' inherent cytotoxic mechanisms and incorporating CAR technology, common CAR-T cell-related limitations can be effectively mitigated. We herein present an overview of the tumoricidal mechanisms, CAR designs, and manufacturing processes of CAR-NK cells, CAR-MΦ, CAR-iNKT cells, CAR-γδT cells, CAR-neutrophils, and iPSC-derived CAR-cells, outlining the advantages, limitations, and potential solutions of these therapeutic strategies.

Optimizing glutamine concentration enhances ex vivo expansion of natural killer cells through improved redox status.

Amino acids are vital components of the serum-free medium that influence the expansion and function of NK cells. This study aimed to clarify the relationship between amino acid metabolism and expansion and cytotoxicity of NK cells. Based on analyzing the mino acid metabolism of NK-92 cells and Design of Experiments (DOE), we optimized the combinations and concentrations of amino acids in NK-92 cells culture medium. The results demonstrated that NK-92 cells showed a pronounced demand for glutamine, serine, leucine, and arginine, in which glutamine played a central role. Significantly, at a glutamine concentration of 13 mM, NK-92 cells expansion reached 161.9 folds, which was significantly higher than 55.5 folds at 2.5 mM. Additionally, under higher glutamine concentrations, NK-92 cells expressed elevated levels of cytotoxic molecules, the level of cytotoxic molecules expressed by NK-92 cells was increased and the cytotoxic rate was 68.42%, significantly higher than that of 58.08% under low concentration. In view of the close relationship between glutamine metabolism and intracellular redox state, we investigated the redox status within the cells. This study demonstrated that intracellular ROS levels in higher glutamine concentrations were significantly lower than those under lower concentration cultures with decreased intracellular GSH/GSSG ratio, NADPH/NADP+ ratio, and apoptosis rate. These findings indicate that NK-92 cells exhibit improved redox status when cultured at higher glutamine concentrations. Overall, our research provides valuable insights into the development of serum-free culture medium for ex vivo expansion of NK-92 cells.

The nuclear factor ID3 endows macrophages with a potent anti-tumour activity.

Macrophage activation is controlled by a balance between activating and inhibitory receptors1-7, which protect normal tissues from excessive damage during infection8,9 but promote tumour growth and metastasis in cancer7,10. Here we report that the Kupffer cell lineage-determining factor ID3 controls this balance and selectively endows Kupffer cells with the ability to phagocytose live tumour cells and orchestrate the recruitment, proliferation and activation of natural killer and CD8 T lymphoid effector cells in the liver to restrict the growth of a variety of tumours. ID3 shifts the macrophage inhibitory/activating receptor balance to promote the phagocytic and lymphoid response, at least in part by buffering the binding of the transcription factors ELK1 and E2A at the SIRPA locus. Furthermore, loss- and gain-of-function experiments demonstrate that ID3 is sufficient to confer this potent anti-tumour activity to mouse bone-marrow-derived macrophages and human induced pluripotent stem-cell-derived macrophages. Expression of ID3 is therefore necessary and sufficient to endow macrophages with the ability to form an efficient anti-tumour niche, which could be harnessed for cell therapy in cancer.

Requirements for human natural killer cells.

'Requirements for Human Natural Killer Cells' is the latest set of guidelines on human NK cells in China, jointly drafted and agreed upon by experts from the Standards Committee of Chinese Society for Cell Biology. This standard specifies requirements for the human natural killer (NK) cells, including the technical requirements, test methods, test regulations, instructions for use, labeling requirements, packaging requirements, storage and transportation requirements, and waste disposal requirements of NK cells. This standard is applicable for the quality control of NK cells, derived from human tissues, or differentiated/transdifferentiated from stem cells. It was originally released by the Chinese Society for Cell Biology on 30 August, 2022. We hope that the publication of these guidelines will promote institutional establishment, acceptance, and execution of proper protocols and accelerate the international standardization of human NK cells for applications.

Generation of Natural Killer Cells from Human Expanded Potential Stem Cells.

The differentiation of natural killer (NK) cells from human pluripotent stem cells allows for research on and the manufacture of clinical-grade cellular products for immunotherapy. Described here is a two-phase protocol that uses a serum-free commercial medium and a cocktail of cytokines (interleukin [IL]-3, IL-7, IL-15, stem cell factor [SCF], and FMS-like tyrosine kinase 3 ligand [Ftl3L]) to differentiate human expanded potential stem cells (hEPSCs) into cells that possess NK cell properties in vitro with both 3-dimensional (3D) and 2-dimensional (2D) culture technology. Following this protocol, CD3-CD56+ or CD45+CD56+ NK cells are consistently generated. When cocultured with tumor targets for 3 h, the differentiated products display mild cytotoxicity as compared to an IL-2-independent permanent cell line, NK92mi cells. The protocol preserves the complexity of the differentiation microenvironment by the generation of 3D structures, thus facilitating the study of the spatial relationships between immune cells and their niches. Meanwhile, the 2D culture system enables the routine phenotypical validation of cell differentiation without harming the delicate differentiation niche.

FOXO1 and FOXO3 Cooperatively Regulate Innate Lymphoid Cell Development.

Natural killer (NK) cells play roles in viral clearance and early surveillance against malignant transformation, yet our knowledge of the underlying mechanisms controlling their development and functions remain incomplete. To reveal cell fate-determining pathways in NK cell progenitors (NKP), we utilized an unbiased approach and generated comprehensive gene expression profiles of NK cell progenitors. We found that the NK cell program was gradually established in the CLP to preNKP and preNKP to rNKP transitions. In line with FOXO1 and FOXO3 being co-expressed through the NK developmental trajectory, the loss of both perturbed the establishment of the NK cell program and caused stalling in both NK cell development and maturation. In addition, we found that the combined loss of FOXO1 and FOXO3 caused specific changes to the composition of the non-cytotoxic innate lymphoid cell (ILC) subsets in bone marrow, spleen, and thymus. By combining transcriptome and chromatin profiling, we revealed that FOXO TFs ensure proper NK cell development at various lineage-commitment stages through orchestrating distinct molecular mechanisms. Combined FOXO1 and FOXO3 deficiency in common and innate lymphoid cell progenitors resulted in reduced expression of genes associated with NK cell development including ETS-1 and their downstream target genes. Lastly, we found that FOXO1 and FOXO3 controlled the survival of committed NK cells via gene regulation of IL-15Rß (CD122) on rNKPs and bone marrow NK cells. Overall, we revealed that FOXO1 and FOXO3 function in a coordinated manner to regulate essential developmental genes at multiple stages during murine NK cell and ILC lineage commitment.

[Villi exosomes deliver HLA-G to enhance the expression of osteoglycin and pleiotrophin in decidual NK cells].

Objective To identify the effect of HLA-G-containing exosomes on the secretory function of growth-promoting factors osteoglycin (OGN) and pleiotrophin (PTN) by decidual NK (dNK) cells. Methods dNK cells were co-cultured with HLA-G-containing exosomes from the villi of patients undergoing unexplained recurrent pregnancy loss (uRPL) and normal induced abortion, respectively. Sequentially, OGN and PTN of the dNK cells were determined using real time quantitative PCR and western blotting. Exosomes overexpressing HLA-G (HLA-GOE-EXO) were obtained by transfecting the villous trophoblast cell line HTR-8/Svneo with lentivirus LV-HLA-G. dNK cells were further co-cultured with HLA-GOE-EXO for detecting the expression of OGN and PTN, the culture supernatant of which was used to treat HTR-8/Svneo cells, and the proliferation of HTR-8/Svneo cells was detected by the CCK-8 assay. Results Exosomes derived from villi of patients receiving normal induced abortion significantly enhanced the expression of OGN and PTN in dNK cells compared with those from patients of the uRPL group. Besides, HLA-GOE-EXO markedly enhanced the expression of OGN and PTN in dNK cells. The culture supernatant of HLA-GOE-EXO treated dNK cells could promote the proliferation of HTR-8/Svneo cells. Conclusion Villi-derived HLA-G containing exosomes may enhance the secretion of growth-promoting factors in dNK cells.

[Expression Level of SOCS3 in Acute Lymphoblastic Leukemia Cells Affects the Cytotoxicity of NK Cells].

OBJECTIVE: To detect the expression level of suppressors of cytokine signaling 3 （SOCS3） in acute lymphoblastic leukemia (ALL), and to observe the effect of over-expresson of SOCS3 in Jurkat cells on the cytotoxicity of NK cells. METHODS: The expression levels of SOCS3 mRNA in peripheral blood mononuclear cells of 20 children with ALL and 20 healthy children (normal control group) were detected by RT-PCR. The peripheral blood NK cells from healthy subjects were selected by immunomagnetic technique, and the purity was detected by flow cytometry. SOCS3 was overexpressed in Jurkat cells infected with lentivirus vector, and SOCS3 mRNA expression was detected by RT-PCR after lentivirus infection. The NK cells were co-cultured with the infected Jurkat, and LDH release method was used to detect the cytotoxicity of NK cells on the infected Jurkat cells. The concentrations of TNF-α and IFN-γ were determined by ELISA. The expression of NKG2D ligands MICA and MICB on the surface of Jurkat cells were detected by flow cytometry. Western blot was used to detect the effect of SOCS3 overexpression on STAT3 phosphorylation in Jurkat cells. RESULTS: Compared with the control group, the mRNA expression of SOCS3 in the peripheral blood mononucleated cells of ALL children was significantly decreased. The purity of NK cells isolated by flow cytometry could reach more than 70%. The expression of SOCS3 mRNA in Jurkat cells increased significantly after lentivirus infection. Overexpression of SOCS3 in Jurkat cells significantly promoted the killing ability of NK cells and up-regulated the secretion of TNF-α and IFN-γ from NK cells. The results of flow cytometry showed that the expression of NKG2D ligands MICA and MICB on Jurkat cells increased significantly after SOCS3 overexpression. Western blot results showed that overexpression of SOCS3 significantly reduced the phosphorylation level of STAT3 protein in Jurkat cells. CONCLUSION: SOCS3 mRNA expression was significantly decreased in ALL patients, and overexpression of SOCS3 may up-regulate the expression of MICA and MICB of NKG2D ligands on Jurkat cell surface through negative regulation of JAK/STAT signaling pathway, thereby promoting the cytotoxic function of NK cells.

R848/TLR7-Mediated Stronger CD8+ T Immunity Is Dependent on DC-NK Cell Interactions.

BACKGROUND: Toll-like receptor (TLR) 7 agonists are effective candidates for Th1 immune adjuvants, which compensate for the insufficient Th1 immune responses induced by traditional adjuvants. This effect is currently dependent on TLR7-mediated induction of dendritic cell (DC) maturation and increased IL-12 production. METHODS: In vivo, we intraperitoneally injected TLR agonists with OVA, and LNs were collected for detection. In vitro, Activated DCs, natural killer (NK) cells, and CD8+ T cells were tested using flow cytometry for surface expression and enzyme-linked immunosorbent assay for cytokine production. NK cell migration was evaluated using transwell system. All experiments were performed in both C57BL/6 and BALB/C backgrounds. RESULTS: Our findings revealed that the enhanced CD8+ T immunity characterized by CD8+ T accumulation, proliferation, and IFN-γ+CD8+ T induction induced by R848 was attributed to DC-dependent NK cell migration and DC-NK interactions. Our results demonstrated that R848 induced CD8+ T cell accumulation and IFN-γ+CD8+ T cells in lymph nodes (LNs) to a greater degree in vivo than TLR4 agonists (lipopolysaccharide) and TLR9 agonists (Class C CPG). R848-activated DCs enhanced CD8+ T cell proliferation and increased IFN-γ+CD8+ T cells with the assistance of NK cells. In contrast, depletion of NK cell decreased IFN-γ+CD8+ T cell production. Greater NK cell migration to LNs occurred in R848-immunized mice. A similar effect of R848 on NK cell migration was observed in an in vitro transwell study. When co-cultured, NK cells plus R848 could promote DCs maturation, and in turn, DCs in combination of R848 augmented NK cells activation. Further studies demonstrated that among several TLR agonists, R848 produced the largest amount of the chemokine CXCL9 from activated DCs, which is relevant to NK cell migration. CXCL9 blockade reduced the number of migrated NK cells, and the addition of CXCL9 increased the number of NK cells. DISCUSSION: Taken together, R848-mediated stronger CD8+ T cell immunity does not depend on DC activation alone, rather that NK cells must also be considered. By increasing our immunological understanding of the effect of R848/TLR7, these findings provide a new perspective for applying R848 in future clinical studies.

Immune landscape of human placental villi using single-cell analysis.

Maintenance of a healthy pregnancy is reliant on a successful balance between the fetal and maternal immune systems. Although the maternal mechanisms responsible have been well studied, those used by the fetal immune system remain poorly understood. Using suspension mass cytometry and various imaging modalities, we report a complex immune system within the mid-gestation (17-23 weeks) human placental villi (PV). Consistent with recent reports in other fetal organs, T cells with memory phenotypes, although rare in abundance, were detected within the PV tissue and vasculature. Moreover, we determined that T cells isolated from PV samples may be more proliferative after T cell receptor stimulation than adult T cells at baseline. Collectively, we identified multiple subtypes of fetal immune cells within the PV and specifically highlight the enhanced proliferative capacity of fetal PV T cells.

Zero-preserving imputation of single-cell RNA-seq data.

A key challenge in analyzing single cell RNA-sequencing data is the large number of false zeros, where genes actually expressed in a given cell are incorrectly measured as unexpressed. We present a method based on low-rank matrix approximation which imputes these values while preserving biologically non-expressed genes (true biological zeros) at zero expression levels. We provide theoretical justification for this denoising approach and demonstrate its advantages relative to other methods on simulated and biological datasets.

Expansion of cytotoxic natural killer cells in multiple myeloma patients using K562 cells expressing OX40 ligand and membrane-bound IL-18 and IL-21.

BACKGROUND: Natural killer (NK) cell-based immunotherapy is a promising treatment approach for multiple myeloma (MM), but obtaining a sufficient number of activated NK cells remains challenging. Here, we report an improved method to generate ex vivo expanded NK (eNK) cells from MM patients based on genetic engineering of K562 cells to express OX40 ligand and membrane-bound (mb) IL-18 and IL-21. METHODS: K562-OX40L-mbIL-18/-21 cells were generated by transducing K562-OX40L cells with a lentiviral vector encoding mbIL-18 and mbIL-21, and these were used as feeder cells to expand NK cells from peripheral blood mononuclear cells of healthy donors (HDs) and MM patients in the presence of IL-2/IL-15. Purity, expansion rate, receptor expression, and functions of eNK cells were determined over four weeks of culture. RESULTS: NK cell expansion was enhanced by short exposure of soluble IL-18 and IL-21 with K562-OX40L cells. Co-culture of NK cells with K562-OX40L-mbIL-18/-21 cells resulted in remarkable expansion of NK cells from HDs (9,860-fold) and MM patients (4,929-fold) over the 28-day culture period. Moreover, eNK cells showed increased expression of major activation markers and enhanced cytotoxicity towards target K562, U266, and RPMI8226 cells. CONCLUSIONS: Our data suggest that genetically engineered K562 cells expressing OX40L, mbIL-18, and mbIL-21 improve the expansion of NK cells, increase activation signals, and enhance their cytolytic activity towards MM cells.