Human CD56dimCD16dim Cells As an Individualized Natural Killer Cell Subset

Bridging the gap with multispecific immune cell engagers in cancer and infectious diseases

By binding to multiple antigens simultaneously, multispecific antibodies are expected to substantially improve both the activity and long-term efficacy of antibody-based immunotherapy. Immune cell engagers, a subclass of antibody-based constructs, consist of engineered structures designed to bridge immune effector cells to their target, thereby redirecting the immune response toward the tumor cells or infected cells. The increasing number of recent clinical trials evaluating immune cell engagers reflects the important role of these molecules in new therapeutic approaches for cancer and infections. In this review, we discuss how different immune cell types (T and natural killer lymphocytes, as well as myeloid cells) can be bound by immune cell engagers in immunotherapy for cancer and infectious diseases. Furthermore, we explore the preclinical and clinical advancements of these constructs, and we discuss the challenges in translating the current knowledge from cancer to the virology field. Finally, we speculate on the promising future directions that immune cell engagers may take in cancer treatment and antiviral therapy.

The role and novel use of natural killer cells in graft-versus-leukemia reactions after allogeneic transplantation

Allogeneic hematopoietic cell transplantation (HCT) has transformed over the past several decades through enhanced supportive care, reduced intensity conditioning (RIC), improved human leukocyte antigen (HLA) typing, and novel graft-versus-host disease (GVHD)-prevention and treatment strategies. Most notably, the implementation of post-transplantation cyclophosphamide (PTCy) has dramatically increased the safety and availability of this life-saving therapy. Given reductions in nonrelapse mortality (NRM) with these advances, the HCT community has placed even greater emphasis on developing ways to reduce relapse - the leading cause of death after HCT. When using RIC HCT, protection from relapse relies predominantly on graft-versus-leukemia (GVL) reactions. Donor lymphocyte infusion (DLI), adoptive cellular therapy, checkpoint inhibition, and post-HCT maintenance strategies represent approaches under study that aim to augment or synergize with the GVL effects of HCT. Optimizing donor selection algorithms to leverage GVL represents another active area of research. Many of these strategies seek to harness the effects of T cells, which for decades were felt to be the primary mediators of GVL and the focus of investigation in relapse reduction. However, there is growing interest in capitalizing on the ability of natural killer (NK) cells to yield potent anti-tumor effects. A potential advantage of NK cell-based approaches over T cell-mediated is the potential to reduce NRM in addition to relapse. By decreasing infection, without increasing the risk of GVHD, NK cells may mitigate NRM, while still yielding relapse reduction through identification and clearance of cancer cells. Most T cell-focused relapse-prevention strategies must weigh the benefits of relapse reduction against the increased risk of NRM from GVHD. In contrast, NK cells have the potential to reduce both, potentially tipping the scales significantly in favor of survival. Here, we will review the role of NK cells in GVL, optimization of NK cell match or mismatch, and burgeoning areas of research in NK cell therapy such as adoptive transfer and chimeric antigen receptor (CAR) NK cells.

A specific natural killer cells phenotypic signature associated to long term elite control of HIV infection

Elite controllers (ECs) are an exceptional group of people living with HIV (PLWH) that control HIV replication without therapy. Among the mechanisms involved in this ability, natural killer (NK)-cells have recently gained much attention. We performed an in-deep phenotypic analysis of NK-cells to search for surrogate markers associated with the long term spontaneous control of HIV. Forty-seven PLWH (22 long-term EC [PLWH-long-term elite controllers (LTECs)], 15 noncontrollers receiving antiretroviral treatment [ART] [PLWH-onART], and 10 noncontrollers cART-naïve [PLWH-offART]), and 20 uninfected controls were included. NK-cells homeostasis was analyzed by spectral flow cytometry using a panel of 15 different markers. Data were analyzed using FCSExpress and R software for unsupervised multidimensional analysis. Six different subsets of NK-cells were defined on the basis of CD16 and CD56 expression, and the multidimensional analysis revealed the existence of 68 different NK-cells clusters based on the expression levels of the 15 different markers. PLWH-offART presented the highest disturbance of NK-cells homeostasis and this was not completely restored by long-term ART. Interestingly, long term spontaneous control of HIV (PLWH-LTEC group) was associated with a specific profile of NK-cells homeostasis disturbance, characterized by an increase of CD16dimCD56dim subset when compared to uninfected controls (UC) group and also to offART and onART groups (p < 0.0001 for the global comparison), an increase of clusters C16 and C26 when compared to UC and onART groups (adjusted p-value < 0.05 for both comparisons), and a decrease of clusters C10 and C20 when compared to all the other groups (adjusted p-value < 0.05 for all comparisons). These findings may provide clues to elucidate markers of innate immunity with a relevant role in the long-term control of HIV.

Lingering Effects of Early Institutional Rearing and Cytomegalovirus Infection on the Natural Killer Cell Repertoire of Adopted Adolescents

Adversity during infancy can affect neurobehavioral development and perturb the maturation of physiological systems. Dysregulated immune and inflammatory responses contribute to many of the later effects on health. Whether normalization can occur following a transition to more nurturing, benevolent conditions is unclear. To assess the potential for recovery, blood samples were obtained from 45 adolescents adopted by supportive families after impoverished infancies in institutional settings (post-institutionalized, PI). Their immune profiles were compared to 39 age-matched controls raised by their biological parents (non-adopted, NA). Leukocytes were immunophenotyped, and this analysis focuses on natural killer (NK) cell populations in circulation. Cytomegalovirus (CMV) seropositivity was evaluated to determine if early infection contributed to the impact of an atypical rearing. Associations with tumor necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ), two cytokines released by activated NK cells, were examined. Compared to the NA controls, PI adolescents had a lower percent of CD56bright NK cells in circulation, higher TNF-α levels, and were more likely to be infected with CMV. PI adolescents who were latent carriers of CMV expressed NKG2C and CD57 surface markers on more NK cells, including CD56dim lineages. The NK cell repertoire revealed lingering immune effects of early rearing while still maintaining an overall integrity and resilience.

Natural killer cell subsets and their functional molecules in peripheral blood of the patients with breast cancer

BACKGROUND

Natural killer (NK) cells, CD3- lymphocytes, are critical players in cancer immune surveillance. This study aimed to assess two types of CD3- NK cell classifications (subsets), that is, convectional subsets (based on CD56 and CD16 expression) and new subsets (based on CD56, CD27, and CD11b expression), and their functional molecules in the peripheral blood of patients with breast cancer (BC) in comparison with healthy donors (HDs).

METHODS

Thirty untreated females with BC and 20 age-matched healthy women were enrolled. Peripheral blood samples were collected and directly incubated with fluorochrome-conjugated antibodies against CD3, CD56, CD16, CD27, CD11b, CD96, NKG2C, NKG2D, NKp44, CXCR3, perforin, and granzyme B. Red blood cells were then lysed using lysing solution, and the stained cells were acquired on four-color flow cytometer.

RESULT

Our results indicated 15% of lymphocytes in peripheral blood of patients with BC and HDs had NK cells phenotype. However, the frequency of total NK cells (CD3-CD56+), and NK subsets (based on conventional and new classifications) was not significantly different between patients and HDs. We observed mean fluorescent intensity (MFI) of CXCR3 in total NK cells (p = .02) and the conventional cytotoxic (CD3-CD56dim CD16+) NK cells (p = .03) were significantly elevated in the patients with BC compared to HDs. Despite this, the MFI of granzyme B expression in conventional regulatory (CD3-CD56brightCD16- /+) NK cells and CD3-CD56-CD16+ NK cells (p = .03 and p = .004, respectively) in the patients was lower than healthy subjects.

CONCLUSION

The higher expression of chemokine receptor CXCR3 on total NK cells in patients with BC may be associated with increased chemotaxis-related NK cell infiltration. However, lower expression of granzyme B in conventional regulatory NK cells and CD3-CD56-CD16+ NK cells in the patients compared to HDs suggests reduced cytotoxic activity of the NK cells in BC. These results might demonstrate accumulating NK subsets with a dysfunctional phenotype in the peripheral blood of patients with BC.

Thymic NK-Cells and Their Potential in Cancer Immunotherapy

Natural killer (NK)-cells are innate immune cells with potent anti-tumor capacity, capable of recognizing target cells without prior exposure. For this reason, NK-cells are recognized as a useful source of cell therapy. Although most NK-cells are derived from the bone marrow (BM), a separate developmental pathway in the thymus also exists, producing so-called thymic NK-cells. Unlike conventional NK-cells, thymic NK (tNK)-cells have a combined capacity for cytokine production and a natural ability to kill tumor cells in the presence of NK-cell receptor stimulatory ligands. Furthermore, tNK-cells are reported to express CD3 subunits intracellularly, without the presence of a rearranged T-cell receptor (TCR). This unique feature may enable harnessing of these cells with a TCR to combine NK- and T-cell effector properties in one cell type. The development, phenotype, and function of tNK-cells, and potential as a cell therapy is, however, poorly explored. In this review, we provide an overview of current literature on both murine and human tNK-cells in comparison to conventional BM-derived NK-cells, and discuss the potential applications of this cellular subset in the context of cancer immunotherapy.

Exploring NK cell receptor dynamics in paediatric leukaemias: implications for immunotherapy and prognosis

Objectives

Immunotherapies targeting natural killer (NK) cell receptors have shown promise against leukaemia. Unfortunately, cancer immunosuppressive mechanisms that alter NK cell phenotype prevent such approaches from being successful. The study utilises advanced cytometry to examine how cancer immunosuppressive pathways affect NK cell phenotypic changes in clinical samples.

Methods

In this study, we conducted a high-dimensional examination of the cell surface expression of 16 NK cell receptors in paediatric patients with acute myeloid leukaemia and acute lymphoblastic leukaemia, as well as in samples of non-age matched adult peripheral blood (APB) and umbilical cord blood (UCB). An unsupervised analysis was carried out in order to identify NK cell populations present in paediatric leukaemias.

Results

We observed that leukaemia NK cells clustered together with UCB NK cells and expressed relatively higher levels of the NKG2A receptor compared to APB NK cells. In addition, CD56dimCD16+CD57- NK cells lacking NKG2A expression were mainly absent in paediatric leukaemia patients. However, CD56br NK cell populations expressing high levels of NKG2A were highly represented in paediatric leukaemia patients. NKG2A expression on leukaemia NK cells was found to be positively correlated with the expression of its ligand, suggesting that the NKG2A-HLA-E interaction may play a role in modifying NK cell responses to leukaemia cells.

Conclusion

We provide an in-depth analysis of NK cell populations in paediatric leukaemia patients. These results support the development of immunotherapies targeting immunosuppressive receptors, such as NKG2A, to enhance innate immunity against paediatric leukaemia.

A Noncanonical CD56dimCD16dim/- NK Cell Subset Indicative of Prior Cytotoxic Activity Is Elevated in Patients with Autoantibody-Mediated Neurologic Diseases

Neuromyelitis optica spectrum disorder (NMOSD), myelin oligodendrocyte glycoprotein Ab disease, and autoimmune myasthenia gravis (MG) are autoantibody-mediated neurologic conditions where autoantibodies can induce Ab-dependent cellular cytotoxicity (ADCC), a NK cell-mediated effector function. However, whether ADCC is a pathogenic mechanism in patients with these conditions has not been confirmed. We sought to characterize circulatory NK cells using functional assays, phenotyping, and transcriptomics to elucidate their role in pathology. NK cells from NMOSD patients and MG patients with elevated disease burden exhibited reduced ADCC and CD56dimCD16hi NK cells, along with an elevated frequency of CD56dimCD16dim/- NK cells. We determined that ADCC induces a similar phenotypic shift in vitro. Bulk RNA sequencing distinguished the CD56dimCD16dim/- population from the canonical CD56dimCD16hi cytotoxic and CD56hiCD16- immunomodulatory subsets, as well as CD56hiCD16+ NK cells. Multiparameter immunophenotyping of NK cell markers, functional proteins, and receptors similarly showed that the CD56dimCD16dim/- subset exhibits a unique profile while still maintaining expression of characteristic NK markers CD56, CD94, and NKp44. Notably, expression of perforin and granzyme is reduced in comparison with CD56dimCD16hi NK cells. Moreover, they exhibit elevated trogocytosis capability, HLA-DR expression, and many chemokine receptors, including CCR7. In contrast with NMOSD and MG, myelin oligodendrocyte glycoprotein Ab disease NK cells did not exhibit functional, phenotypic, or transcriptomic perturbations. In summary, CD56dimCD16dim/- NK cells are a distinct peripheral blood immune cell population in humans elevated upon prior cytotoxic activity by the CD56dimCD16hi NK cell subset. The elevation of this subset in NMOSD and MG patients suggests prior ADCC activity.

Association of NK cell subsets and cytotoxicity with FCGR3A gene polymorphism in functional NK cell deficiency

OBJECTIVE

The purpose of this study was to assess the association between clinical, laboratory, and functional analyses and polymorphism in the FCGR3A gene in individuals with functional NK cell deficiency.

METHODS

A total of 15 functional NK cell deficiency patients and 10 age-matched healthy controls underwent NK cell subgroup, cytotoxicity, and FCGR3A whole-exome analysis with next-generation sequencing.

RESULTS

Three different NK cell subsets (CD56brightCD16neg, CD56brightCD16int, and CD56dimCD16hi) were identified. No statistically significant difference was found in the ratio of CD56brightCD16neg cells between patients and controls. CD56brightCD16int and CD56dimCD16hi ratios were found to be significantly lower in patients. As a result of NK cell cytotoxicity analysis, a proportional decrease of K562 amount between patients and controls was found to be statistically significant (p<0.001). In the FCGR3A whole-exome analysis, all patients were found to be homozygous mutant for the c.526G > T (p.V176F) in exon 4, while three patients were homozygous wild type and 12 patients were heterozygous for the c.197T>A (p.L66H) in exon 3.

CONCLUSION

In this study, a group of pediatric patients with suspected functional NK cell deficiency were evaluated and the findings indicated that NK subsets, cytotoxicity results, and FCGR3A gene polymorphism were found to be correlated with the clinical features. We conclude that this kind of study might contribute to follow-up the patients in time.

Distinctive CD56dim NK subset profiles and increased NKG2D expression in blood NK cells of Parkinson's disease patients

Mounting data suggest an important role for the immune system in Parkinson's disease (PD). Previous evidence of increased natural killer (NK) cell populations in PD suggests a potential role of NK cells in the pathogenesis of the disease. Previous studies have analyzed NK cell populations using aggregation by variable expression of CD56 and CD16. It remains unknown what differences may exist between NK cell subpopulations when stratified using more nuanced classification. Here, we profile NK cell subpopulations and elucidate the expressions of activating, NKG2D, inhibitory, NKG2A, and homing, CX3CR1, receptors on NK cell subpopulations in PD and healthy controls (HC). We analyzed cryopreserved PMBC samples using a 10-color flow cytometry panel to evaluate NK cell subpopulations in 31 individuals with sporadic PD and 27 HC participants. Here we identified significant differences in the CD56dim NK subset that changes with disease severity in PD. Furthermore, the expressions of NKG2D in all three NK cell subsets were significantly elevated in PD patients compared to HC. Notably, NKG2A expression in the CD56bright NK subset increased in PD patients with longer disease duration but there were no changes in CX3CR1. In summary, our data suggests that changes in NK cells may be influenced by the clinical severity and duration of PD.

Outlining the skin-homing and circulating CLA+NK cells in patients with severe atopic dermatitis

Atopic dermatitis (AD) is a complex, multifactorial skin disease, characterized by pruritus and predominant Th2 inflammation. Innate immune cells may play a role in AD development and are composed of granulocytes, macrophages, innate-like T cells, and innate lymphoid cells. This study investigates the phenotypic and functional profile of circulating CLA+ natural killer (NK) cells and its role in the skin-homing to NK cells infiltrated in adults' skin with AD. We selected 44 AD patients and 27 non-AD volunteers for the study. The results showed increased frequencies of both CLA+CD56bright and CLA+CD56dim NK cell populations in the peripheral blood, mainly in severe AD patients. Upon SEB stimulation, we observed an augmented percentage of CLA+CD56dim NK cells expressing CD107a, IFN-γ, IL-10, and TNF, reinforcing the role of staphylococcal enterotoxins in AD pathogenesis. Additionally, we demonstrated increased dermal expression of both NK cell markers NCAM-1/CD56 and pan-granzyme, corroborating the skin-homing, mostly in severe AD. Further studies are necessary to elucidate the potential role of NK cells in the chronification of the inflammatory process in AD skin, as well as their possible relationship with staphylococcal enterotoxins, and as practicable therapeutic targets.

Association of recurrent implantation failure and recurrent pregnancy loss with peripheral blood natural killer cells and interferon-gamma level

OBJECTIVE

Fetal uterine survival depends on maintaining an immune balance between the mother and fetus. This study aimed to investigate the correlation of blood peripheral natural killer (NK) cells and interferon-gamma (IFN-γ) with recurrent recurrent implantation failure (RIF) and recurrent pregnancy loss (RPL).

METHODS

In this case-control study, peripheral blood samples were obtained from three groups of RPL, RIF, and parous women without a history of abortion or infertility problems and analyzed by lymphocyte-based flow cytometry. Afterward, the levels of NK cells and IFN-γ were determined. All data were analyzed using one-way analysis of variance and nonparametric Kruskal-Wallis tests.

RESULTS

The level of IFN-γ in the RPL group was significantly higher than that in parous women and the RIF group (P<0.05), whereas its level in the RIF group was not significantly different from the control group (P>0.05). A significant correlation was found between the levels of IFN-γ and NK cells in the RPL group (r=0.481; P=0.02). However, no significant correlation was found between the levels of IFN-γ and the active NK cells in the RPL group (P=0.08). Moreover, no significant correlation was found between the levels of NK cells (whether activated or not) and IFN-γ in the RIF patients (P>0.05).

CONCLUSION

Immune dysfunction may not be involved in implantation failure during IVF but may be involved in recurrent miscarriage, probably by increasing IFN-γ levels.

Mediastinal lymph node removal modulates natural killer cell exhaustion in patients with non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related death globally. In this study, the effect of complete removal of mediastinal lymph nodes by video-assisted mediastinoscopic lymphadenectomy (VAMLA) on natural killer (NK) cell phenotype and functions in patients with NSCLC was evaluated. The study included 21 NSCLC patients (cIA-IVA) undergoing VAMLA staging and 33 healthy controls. Mononuclear cells were isolated from peripheral blood of all participants and mediastinal lymph nodes of the patients. NK cells were analyzed by flow cytometry to define NK subsets, expressions of PD-1, CTLA-4, activating/inhibitory receptors, granzyme A, and CD107a. The plasma levels of soluble PD-1, PDL-1, and CTLA-4 were measured by ELISA. Mediastinal lymph nodes of NSCLC patients had increased ratios of exhausted NK cells, increased expression of PD-1 and IL-10, and impaired cytotoxicity. Mediastinal lymph nodes removal increased CD56dimCD16bright cytotoxic effector phenotype and reduced exhausted NK cells. PD-1+ NK cells were significantly more abundant in patients' blood, and VAMLA significantly reduced their ratio as well. The ratio of IL-10 secreting regulatory NK cells was also reduced after VAMLA. Blood NK cells had increased cytotoxic functions and spontaneous IFN-γ secretion, and these NK cell functions were also recovered by VAMLA. Mediastinal lymph node removal reversed NK cell exhaustion, reduced regulatory NK cells, and improved antitumoral functions of NK cells. Tumor-draining lymph nodes may contribute to tumor evasion from antitumoral immune responses. The role of their removal needs to be further studied both to better understand this mechanism and as a potential immunotherapeutic approach.

Effect of infiltrating immune cells in tumor microenvironment on metastasis of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most lethal and prevalent human malignancies, leading to poor prognosis due to its high recurrence and metastasis rates. In recent years it has become increasingly evident that the tumor microenvironment (TME) plays an important role in tumor progression and metastasis. Tumor microenvironment (TME) refers to the complex tissue environment of tumor occurrence and development. Here, we summarize the development of HCC and the role of cellular and non-cellular components of the TME in the metastasis HCC, with particular reference to tumor-infiltrating immune cells. We also discuss some of the possible therapeutic targets for the TME and the future prospectives of this evolving field. SIGNIFICANCE: This review provides a comprehensive analysis of the role of the infiltrating immune cells in TME in the metastasis of HCC and highlights the future outlook for targeted therapy of the TME in the context of recent experiments revealing a number of therapeutic targets targeting the TME.

Activated NK Cells with Pro-inflammatory Features are Associated with Atherogenesis in Perinatally HIV-Acquired Adolescents

Human immunodeficiency virus (HIV) is associated with persistent immune activation and dysfunction in people with HIV despite treatment with antiretroviral therapy (ART). Modulation of the immune system may be driven by: low-level HIV replication, co-pathogens, gut dysbiosis /translocation, altered lipid profiles, and ART toxicities. In addition, perinatally acquired HIV (PHIV) and lifelong ART may alter the development and function of the immune system. Our preliminary data and published literature suggest reprogramming innate immune cells may accelerate aging and increase the risk for future end-organ complications, including cardiovascular disease (CVD). The exact mechanisms, however, are currently unknown. Natural killer (NK) cells are a highly heterogeneous cell population with divergent functions. They play a critical role in HIV transmission and disease progression in adults. Recent studies suggest the important role of NK cells in CVDs; however, little is known about NK cells and their role in HIV-associated cardiovascular risk in PHIV adolescents. Here, we investigated NK cell subsets and their potential role in atherogenesis in PHIV adolescents compared to HIV-negative adolescents in Uganda. Our data suggest, for the first time, that activated NK subsets in PHIV adolescents may contribute to atherogenesis by promoting plasma oxidized low-density lipoprotein (Ox-LDL) uptake by vascular macrophages.

Cytotoxic NK cells phenotype and activated lymphocytes are the main characteristics of patients with alcohol-associated liver disease

T cells, natural killer (NK) and NKT cells have opposing actions in the development of alcohol-associated liver fibrosis. We aimed to evaluate the phenotype of NK cells, NKT cells and activated T cells in patients with alcohol use disorder (AUD) according to the presence of advanced liver fibrosis (ALF). Totally, 79 patients (51-years, 71% males) were admitted to treatment of AUD. ALF was defined as FIB4-score > 2.67. Immunophenotyping of NK cells (CD3-CD56+CD16+, CD3-CD56+CD16-, CD3-CD56-CD16+), NKT-like (CD3+CD56+), and the activation status of CD4+, CD8+ and regulatory T cells (Tregs) were evaluated according to the HLA-DR expression. Patients had an AUD duration of 18 ± 11 years with a daily alcohol consumption of 155 ± 77 gr/day prior to hospital admission. The values of absolute cells were 2 ± 0.9 cells/L for total lymphocytes, 1054 ± 501 cells/µL for CD4+, 540 ± 335 cells/µL for CD8+, 49.3 ± 24.8 cells/µL for Tregs, 150.3 ± 97.5 cells/µL for NK cells and 69.8 ± 78.3 cells/µL for NKT-like. The percentage of total NK cells (11.3 ± 5.5% vs. 7 ± 4.3%, p < 0.01), CD3-CD56+CD16+ regarding total lymphocytes (9.7 ± 5.1% vs. 5.8 ± 3.9%, p < 0.01), activated CD4+ cells (5.2 ± 3.2% vs. 3.9 ± 3%, p = 0.04) and activated CD8+ cells (15.7 ± 9.1% vs. 12.2 ± 9%, p = 0.05) were significantly higher in patients with ALF. The percentage of CD3-CD56+CD16- regarding NK cells (5.1 ± 3.4% vs. 7.6 ± 6.2%, p = 0.03) was significantly lower in patients with ALF. Activated Tregs (39.9 ± 11.5 vs. 32.4 ± 9.2, p = 0.06) showed a tendency to be higher in patients with ALF. The proportion of activated CD4+ cells (r = 0.40, p < 0.01) and activated CD8+ cells (r = 0.51, p < 0.01) was correlated with the proportion of NKT-like in patients without ALF. Patients with ALF presented an increased NK cytotoxic phenotype and activated T cells concomitant with a decreased NK cytokine-secreting phenotype.

Harnessing Natural Killer Cells for Lung Cancer Therapy

Lung cancer is the leading cause of cancer-related death worldwide. Although natural killer (NK) cells are garnering interest as a potential anticancer therapy because they selectively recognize and eliminate cancer cells, their use in treating solid tumors, including lung cancer, has been limited due to impediments to their efficacy, such as their limited ability to reach tumor tissues, the reduced antitumor activity of tumor-infiltrating NK cells, and the suppressive tumor microenvironment (TME). This comprehensive review provides an in-depth analysis of the cross-talk between the lung cancer TME and NK cells. We highlight the various mechanisms used by the TME to modulate NK-cell phenotypes and limit infiltration, explore the role of the TME in limiting the antitumor activity of NK cells, and discuss the current challenges and obstacles that hinder the success of NK-cell-based immunotherapy for lung cancer. Potential opportunities and promising strategies to address these challenges have been implemented or are being developed to optimize NK-cell-based immunotherapy for lung cancer. Through critical evaluation of existing literature and emerging trends, this review provides a comprehensive outlook on the future of NK-cell-based immunotherapy for treating lung cancer.

Longitudinal evaluation of innate immune responses to three doses of CoronaVac vaccine

The adaptive immune responses induced by inactivated COVID-19 vaccine has been extensively studied. However, few studies have analyzed the impact of COVID-19 vaccination on innate immune cells. Here in this study, we recruited 62 healthcare workers who received three doses of CoronaVac vaccine and longitudinally profiled the alterations of peripheral monocytes and NK cells during vaccination. The results showed that both the monocyte and NK cell subsets distribution were altered, although the frequencies of the total monocyte and NK cells remained stable during the vaccination. Additionally, we found that both the 2nd and 3rd dose of CoronaVac vaccination elicited robust IFN-γ-producing NK cell response. Our data provided necessary insights on innate immune responses in the context of three homologous CoronaVac dose vaccination, and supplied immunological basis for the future design of inactivated vaccines against SARS-CoV-2 or other viruses.

Immunology of cord blood T-cells favors augmented disease response during clinical pediatric stem cell transplantation for acute leukemia

Allogeneic hematopoietic stem cell transplantation (HSCT) has been an important and efficacious treatment for acute leukemia in children for over 60 years. It works primarily through the graft-vs.-leukemia (GVL) effect, in which donor T-cells and other immune cells act to eliminate residual leukemia. Cord blood is an alternative source of stem cells for transplantation, with distinct biological and immunological characteristics. Retrospective clinical studies report superior relapse rates with cord blood transplantation (CBT), when compared to other stem cell sources, particularly for patients with high-risk leukemia. Xenograft models also support the superiority of cord blood T-cells in eradicating malignancy, when compared to those derived from peripheral blood. Conversely, CBT has historically been associated with an increased risk of transplant-related mortality (TRM) and morbidity, particularly from infection. Here we discuss clinical aspects of CBT, the unique immunology of cord blood T-cells, their role in the GVL effect and future methods to maximize their utility in cellular therapies for leukemia, honing and harnessing their antitumor properties whilst managing the risks of TRM.

Decreased Expression of CD314 by NK Cells Correlates with Their Ability to Respond by Producing IFN-γ after BCG Moscow Vaccination and Is Associated with Distinct Early Immune Responses

The immune response to vaccines is complex and results in various outcomes. BCG vaccination induces innate and specific responses that can lead to protection against tuberculosis, and cross-protection against other infections. NK cells have been associated with BCG-induced protection. Therefore, we hypothesize that differences in NK cell status before BCG vaccination may have a role in the ability of BCG to activate the immune response. Participants of a clinical trial were evaluated after BCG vaccination. The participants were assigned to different groups according to variation in IFN-γ expression by NK cells between days 1 and 15 after BCG vaccination. Individuals that presented a higher increase in IFN-γ expression by NK cells presented reduced CD314 expression at day 1, and after vaccination an increase in inflammatory NK cells and CD4 T-cell expression of IL-17. A negative correlation between expression of CD314 at day 1 and that of IFN-γ by NK cells after BCG vaccination was observed. Participants with lower of IFN-γ expression by NK cells after BCG vaccination presented an increase in the cytotoxic NK subpopulation and CD4 T-cell expression of IL-17 and IFN-γ. In conclusion, the expression of CD314 by NK cells before BCG vaccination influences their IFN-γ responses, generation of NK subpopulations, and the specific T immune response at 15 days after vaccination.

Anti-Inflammatory Effects of Nutritionally Relevant Concentrations of Oleuropein and Hydroxytyrosol on Peripheral Blood Mononuclear Cells: An Age-Related Analysis

Immunosenescence and inflammaging facilitate the insurgence of chronic diseases. The Mediterranean diet is a non-invasive intervention to improve the chronic low-grade inflammatory status associated with aging. Olive oil oleuropein (OLE) and hydroxytyrosol (HT) demonstrated a controversial modulatory action on inflammation in vitro when tested at concentrations exceeding those detectable in human plasma. We studied the potential anti-inflammatory effects of OLE and HT at nutritionally relevant concentrations on peripheral blood mononuclear cells (PBMCs) as regards cell viability, frequency of leukocyte subsets, and cytokine release, performing an age-focused analysis on two groups of subjects: Adult (age 18-64 years) and Senior (age ≥ 65 years). OLE and HT were used alone or as a pre-treatment before challenging PBMCs with lipopolysaccharide (LPS). Both polyphenols had no effect on cell viability irrespective of LPS, but 5 µM HT had an LPS-like effect on monocytes, reducing the intermediate subset in Adult subjects. OLE and HT had no effect on LPS-triggered release of TNF-α, IL-6 and IL-8, but 5 µM HT reduced IL-10 secretion by PBMCs from Adult vs. Senior group. In summary, nutritionally relevant concentrations of OLE and HT elicit no anti-inflammatory effect and influence the frequency of immune cell subsets with age-related different outcomes.

Microbiota Regulates Pancreatic Cancer Carcinogenesis through Altered Immune Response

The microbiota is present in many parts of the human body and plays essential roles. The most typical case is the occurrence and development of cancer. Pancreatic cancer (PC), one of the most aggressive and lethal types of cancer, has recently attracted the attention of researchers. Recent research has revealed that the microbiota regulates PC carcinogenesis via an altered immune response. Specifically, the microbiota, in several sites, including the oral cavity, gastrointestinal tract, and pancreatic tissue, along with the numerous small molecules and metabolites it produces, influences cancer progression and treatment by activating oncogenic signaling, enhancing oncogenic metabolic pathways, altering cancer cell proliferation, and triggering chronic inflammation that suppresses tumor immunity. Diagnostics and treatments based on or in combination with the microbiota offer novel insights to improve efficiency compared with existing therapies.

The CD56-CD16+ NK cell subset in chronic infections

Long-term human diseases can shape the immune system, and natural killer (NK) cells have been documented to differentiate into distinct subsets specifically associated with chronic virus infections. One of these subsets found in large frequencies in HIV-1 are the CD56-CD16+ NK cells, and this population's association with chronic virus infections is the subject of this review. Human NK cells are classically defined by CD56 expression, yet increasing evidence supports the NK cell status of the CD56-CD16+ subset which we discuss herein. We then discuss the evidence linking CD56-CD16+ NK cells to chronic virus infections, and the potential immunological pathways that are altered by long-term infection that could be inducing the population's differentiation. An important aspect of NK cell regulation is their interaction with human leukocyte antigen (HLA) class-I molecules, and we highlight work that indicates both virus and genetic-mediated variations in HLA expression that have been linked to CD56-CD16+ NK cell frequencies. Finally, we offer a perspective on CD56-CD16+ NK cell function, taking into account recent work that implies the subset is comparable to CD56+CD16+ NK cell functionality in antibody-dependent cell cytotoxicity response, and the definition of CD56-CD16+ NK cell subpopulations with varying degranulation capacity against target cells.

Suppression of CD56bright NK cells in breast cancer patients is associated with the PD-1 and TGF-βRII expression

BACKGROUND

Natural killer (NK) cells, as professional cytotoxic cells, play a key role against cancer in the early and metastatic stages. Their functional defects are highly associated with the initiation or progression of breast cancer (BC). Here, we investigated the phenotypic characterization of NK cells in 26 newly diagnosed BC patients in comparison to 12 healthy counterparts.

METHODS

Expression of CXCR3 and PD-1, and also NKG2D, and TGF-βRII were studied on CD56^dim and CD56^bright NK cells from fresh peripheral blood (PB) samples using flow cytometry. The plasma levels of IFN-γ and soluble MIC-A levels were also assessed by ELISA.

RESULTS

Both CD56^dim and CD56^bright NK subtypes showed lower CXCR3 and NKG2D expression in BC patients than healthy subjects. Furthermore, patients' CD56^bright NK cells significantly showed higher expression levels of TGF-βRII and PD-1. Interestingly, increased concentration of MIC-A level in plasma of BC patients was associated with the higher TGF-βRII and PD-1 expression in all NK cells, while the plasma level of IFN-γ was associated with the lower TGF-βRII expression on CD56^bright NK cells in these patients.

CONCLUSION

Our results demonstrated phenotypically suppressed-NK cells, especially in the CD56^bright subset of BC patients. It specifies their potential incompetence and outlines decrement of their anti-tumor activity, which could be interrelated with the tumor pathogenesis, TME immunosuppression, and so disease progression. The induction of compensatory mechanisms revives NK cells function and could be used in combination with the conventional treatments as a putative therapeutic approach for targeted immunotherapy.

NK cells are never alone: crosstalk and communication in tumour microenvironments

Immune escape is a hallmark of cancer. The dynamic and heterogeneous tumour microenvironment (TME) causes insufficient infiltration and poor efficacy of natural killer (NK) cell-based immunotherapy, which becomes a key factor triggering tumour progression. Understanding the crosstalk between NK cells and the TME provides new insights for optimising NK cell-based immunotherapy. Here, we present new advances in direct or indirect crosstalk between NK cells and 9 specialised TMEs, including immune, metabolic, innervated niche, mechanical, and microbial microenvironments, summarise TME-mediated mechanisms of NK cell function inhibition, and highlight potential targeted therapies for NK-TME crosstalk. Importantly, we discuss novel strategies to overcome the inhibitory TME and provide an attractive outlook for the future.

Antiphospholipid antibody-mediated NK cell cytotoxicity

Antiphospholipid syndrome (APS) is an autoimmune thrombophilia that is characterised by thrombosis and obstetric complications in the presence of antiphospholipid antibodies (aPL). Pregnancy complications remain a challenging problem for patients with APS, especially during the first trimester. Although natural killer (NK) cells constitute up to 70% of decidual lymphocytes during the first trimester, their contribution to early pregnancy loss in APS is largely unknown. We aimed to analyse whether aPL are able to recruit antibody-dependent cellular cytotoxicity (ADCC) of NK cells, with special emphasis on the differences in the effects of aPL containing anti-β2GPI domain 1 (anti-β2GPI-D1) antibodies (aPL+/D1+) and those that do not (aPL+/D1-). Our findings revealed a differential distribution of NK subsets in the presence of different aPL. Namely, aPL+/D1- IgGs increased CD56^dim/CD16^dim cells, while aPL+/D1 + IgGs increased the number of CD56^bright/CD16^dim cells. ADCC NK cell cytotoxicity was found to be higher in the presence of aPL+/D1- IgGs, as defined by an increased target cell death, degranulation and increased expression of CD11b, CD69 and NKG2D. Overall, our evidence showed that aPL are able to recruit ADCC, suggesting NK cells as candidate cells for APS-related obstetric complications.

Combined flow cytometry natural killer immunophenotyping and KIR/HLA-C genotyping reveal remarkable differences in acute myeloid leukemia patients, but suggest an overall impairment of the natural killer response

Introduction

Natural killer (NK) cells are key anti-tumor effectors of the innate immunity. Phenotypic differences allow us to discriminate in between three functional stages of maturation, named immature, mature and hypermature that are distinctive in terms of receptor expression, cytokine secretion, cytotoxic properties and organ trafficking. NKs display an impressive repertoire of highly polymorphic germline encoded receptors that can be either activating, triggering the effector's function, or inhibitory, limiting the immune response. In our study, we have investigated peripheral blood NK cells of acute myeloid leukemia (AML) patients.

Methods

The Killer Immunoglobulin-like receptors (KIRs) and the HLA-C genotypes were assessed, as HLA-C molecules are cognate antigens for inhibitory KIRs.

Results

The AA mainly inhibitory KIR haplotype was found in a higher proportion in AML, while a striking low frequency of the 2DS3 characterized the mainly activating Bx haplotype. Flow cytometry immunophenotyping evidenced a lower overall count of NK cells in AML versus healthy controls, with lower percentages of the immature and mature subpopulations, but with a markedly increase of the hypermature NKs. The analysis of the KIR2DL1, KIR2DL2, KIR2DL3, KIR3DL1, and NKG2A inhibitory receptors surface expression revealed a remarkable heterogeneity. However, an overall trend for a higher expression in AML patients could be noticed in all maturation subpopulations. Some of the AML patients with complex karyotypes or displaying a FLT3 gene mutation proved to be extreme outliers in terms of NK cells percentages or inhibitory receptors expression.

Discussion

We conclude that while the genetic background investigation in AML offers important pieces of information regarding susceptibility to disease or prognosis, it is flow cytometry that is able to offer details of finesse in terms of NK numbers and phenotypes, necessary for an adequate individual evaluation of these patients.

Single-cell transcriptomics in bone marrow delineates CD56dimGranzymeK+ subset as intermediate stage in NK cell differentiation

Human natural killer (NK) cells in lymphoid tissues can be categorized into three subsets: CD56^brightCD16⁺, CD56^dimCD16⁺ and CD69⁺CXCR6⁺ lymphoid tissue-resident (lt)NK cells. How the three subsets are functionally and developmentally related is currently unknown. Therefore, we performed single-cell RNA sequencing combined with oligonucleotide-conjugated antibodies against CD56, CXCR6, CD117 and CD34 on fresh bone marrow NK cells. A minor CD56^dimGzmK⁺ subset was identified that shared features with CD56^bright and CD56^dimGzmK^- NK cells based on transcriptome, phenotype (NKG2A^highCD16^lowKLRG1^highTIGIT^high) and functional analysis in bone marrow and blood, supportive for an intermediate subset. Pseudotime analysis positioned CD56^bright, CD56^dimGzmK⁺ and CD56^dimGzmK^- cells in one differentiation trajectory, while ltNK cells were developmentally separated. Integrative analysis with bone marrow cells from the Human Cell Atlas did not demonstrate a developmental connection between CD34⁺ progenitor and NK cells, suggesting absence of early NK cell stages in bone marrow. In conclusion, single-cell transcriptomics provide new insights on development and differentiation of human NK cells.

Burn-injured skin is marked by a prolonged local acute inflammatory response of innate immune cells and pro-inflammatory cytokines

The systemic and local immune response in burn patients is often extreme and derailed. As excessive inflammation can damage healthy tissues and slow down the healing process, modulation of inflammatory responses could limit complications and improve recovery. Due to its complexity, more detailed information on the immune effects of thermal injury is needed to improve patient outcomes. We therefore characterized and quantified subsets of immune cells and mediators present in human burn wound tissue (eschar), sampled at various time points. This study shows that after burn injury, the number of immune cells were persistently increased, unlike the normal wound healing process. There was an immediate, strong increase in neutrophils and a moderate increase in monocytes/macrophages and lymphocytes, especially in the second and third week post burn. The percentage of classical (CD14highCD16-) monocytes/macrophages demonstrated a steady decrease over time, whereas the proportion of intermediate (CD14highCD16+) monocytes/macrophages slowly increased. The absolute numbers of T cells, NK cells and B cells increased up to week 3, while the fraction of γδ T cells was increased only in week 1. Secretome profiling revealed high levels of chemokines and an overall pro-inflammatory cytokine milieu in burn tissue. The local burn immune response shows similarities to the systemic immune reaction, but differs in neutrophil maturity and lymphocyte composition. Altogether, the neutrophil surges, high levels of pro-inflammatory cytokines and limited immunosuppression might be key factors that prolong the inflammation phase and delay the wound healing process in burns.

Dynamic Evaluation of Natural Killer Cells Subpopulations in COVID-19 Patients

The aim of the study was to evaluate the dynamic changes of the total Natural Killer (NK) cells and different NK subpopulations according to their differentiated expression of CD16/CD56 in COVID-19 patients. Blood samples with EDTA were analyzed on day 1 (admission moment), day 5, and day 10 for the NK subtypes. At least 30,000 singlets were collected for each sample and white blood cells were gated in CD45/SSC and CD16/CD56 dot plots of fresh human blood. From the lymphocyte singlets, the NK cells subpopulations were analyzed based on the differentiated expression of surface markers and classified as follows: CD16^-CD56^+/++/CD16⁺CD56⁺⁺/CD16⁺CD56⁺/CD16⁺⁺CD56⁻. By examining the CD56 versus CD16 flow cytometry dot plots, we found four distinct NK sub-populations. These NK subtypes correspond to different NK phenotypes from secretory to cytolytic ones. There was no difference between total NK percentage of different disease forms. However, the total numbers decreased significantly both in survivors and non-survivors. Additionally, for the CD16^-CD56^+/++ phenotype, we observed different patterns, gradually decreasing in survivors and gradually increasing in those with fatal outcomes. Despite no difference in the proportion of the CD16⁻CD56⁺⁺ NK cells in survivors vs. non–survivors, the main cytokine producers gradually decline during the study period in the survival group, underling the importance of adequate IFN production during the early stage of SARS-CoV-2 infection. Persistency in the circulation of CD56⁺⁺ NK cells may have prognostic value in patients, with a fatal outcome. Total NK cells and the CD16⁺CD56⁺ NK subtypes exhibit significant decreasing trends across the moments for both survivors and non-survivors.

Engineering of immune checkpoints B7-H3 and CD155 enhances immune compatibility of MHC-I-/- iPSCs for β cell replacement

Induced pluripotent stem cells (iPSCs) represent a source from which β cells can be derived for diabetes replacement therapy. However, their application may be hindered by immune-mediated responses. Although abrogation of major histocompatibility complex class I (MHC-I) can address this issue, it may trigger natural killer (NK) cells through missing-self recognition mechanisms. By profiling the relevant NK-activating ligands on iPSCs during in vitro differentiation into pancreatic β cells, we find that they express high levels of B7-H3 and CD155. Hypothesizing that such surface ligands could be involved in the amplification of NK-activating signals following missing-self, we generate MHC-I-deprived B7-H3^−/−, CD155^−/−, and B7-H3^−/−/CD155^−/− iPSCs. All engineered lines correctly differentiate into insulin-secreting β cells and are protected from cell lysis mediated by CD16_dim and CD16⁺ NK subpopulations both in vitro and in vivo in NSG mice. Our data support targeted disruption of NK-activating ligands to enhance the transplant compatibility of MHC-I^−/− iPSC pancreatic derivatives.

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MHC-I^−/− cells are killed by NK cells via missing-self recognition mechanisms

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Stem cell-derived pancreatic progenitors (PPs) express B7-H3 and CD155 NK ligands

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B7-H3/CD155 knockout (KO) prevents killing of the MHC-I^−/− cells by NKs in vitro

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B7-H3/CD155 KO increases immune compatibility of MHC-I^−/− PPs in a mouse model

CD56-negative NK cells: Frequency in peripheral blood, expansion during HIV-1 infection, functional capacity, and KIR expression

Human NK cells are usually defined as CD3-CD56+ lymphocytes. However, a CD56-CD16+ (CD56neg) lymphocyte population that displays NK-associated markers expands during chronic viral infections such as HIV-1 and HCV, and, to lesser extent, in herpesvirus infections. This CD56neg NK cell subset has been understudied because it requires the exclusion of other lymphocytes to accurately identify its presence. Many questions remain regarding the origin, development, phenotype, and function of the CD56neg NK cell population. Our objective was to determine the frequency of this NK subset in healthy controls and its alteration in viral infections by performing a meta-analysis. In addition to this, we analyzed deposited CyTOF and scRNAseq datasets to define the phenotype and subsets of the CD56neg NK cell population, as well as their functional variation. We found in 757 individuals, from a combined 28 studies and 6 datasets, that the CD56neg subset constitutes 5.67% of NK cells in healthy peripheral blood, while HIV-1 infection increases this population by a mean difference of 10.69%. Meta-analysis of surface marker expression between NK subsets showed no evidence of increased exhaustion or decreased proliferation within the CD56neg subset. CD56neg NK cells have a distinctive pattern of KIR expression, implying they have a unique potential for KIR-mediated education. A perforin-CD94-NKG2C-NKp30- CD56neg population exhibited different gene expression and degranulation responses against K562 cells compared to other CD56neg cells. This analysis distinguishes two functionally distinct subsets of CD56neg NK cells. They are phenotypically diverse and have differing capacity for education by HLA class-I interactions with KIRs.

Diagnostic Value of Natural Killer Cells, CD56+ CD16+ Natural Killer Cells, NLRP3, and Lactate Dehydrogenase in Severe/Critical COVID-19: A Prospective Longitudinal Study According to the Severe/Critical COVID-19 Definitions

Innate immunity, as the first line of defense of our immune system, plays a crucial role in defending against SARS-CoV-2 infection and also its immunopathogenesis. We aim to investigate the immune status of natural killer (NK) cells, natural killer T (NKT) cells, and NLRP3 gene expression in COVID-19 patient blood samples. The immunophenotype of NK cell subsets and NKT cells was detected by flow cytometry and the expression of NLRP3 gene assessed by reverse transcriptase real-time polymerase chain reaction in 44 COVID-19 patients and 20 healthy individuals. The percentage of most of NK cell subpopulation and NKT cells was significantly decreased in COVID-19 patients. The percentage of CD56dim CD16- NK cell subsets, and NLRP3 gene expression increased. The percentage of total NK cells, CD56+ CD16+ NK cells, and NLRP3 gene expression had acceptable sensitivity and specificity for assisting diagnosis of severe/critical COVID-19. O₂ saturation% and lactate dehydrogenase levels showed valuable diagnostic value to identify critical cases. The declined NK and NKT cells in COVID-19 patients and enhanced NLRP3 gene expression were associated with disease severity. Total NK cells, CD56+ CD16+ NK cells, and NLRP3 gene expression might be used as meaningful indicators for assisting diagnosis of severe/critical COVID-19.

Safety and Efficacy of Allogeneic Natural Killer Cells in Combination with Pembrolizumab in Patients with Chemotherapy-Refractory Biliary Tract Cancer: A Multicenter Open-Label Phase 1/2a Trial

Background and Aim: This study investigated the administration of combination therapy, allogeneic natural killer (NK) cells and pembrolizumab in the treatment of advanced biliary tract cancer to determine the safety and tolerability (phase 1) and the efficacy and safety (phase 2a). Methods: Forty patients (phase 1, n = 6; phase 2a, n = 34) were enrolled between December 2019 and June 2021. The patients received highly activated allogeneic NK cells (“SMT-NK”) on weeks 1 and 2 and pembrolizumab on week 1. This 3-week schedule (one cycle) was repeated until confirmed disease progression, intolerable adverse events (AEs), patient withdrawal, or finishing the maximum treatment schedule. The tumor response was evaluated after every three cycles. Results: In phase 1, four patients (66.7%) experienced seven AEs, but no severe AE was observed. In phase 2a, 126 AEs occurred in 29 patients (85.3%). Severe AEs (≥grade 3) were reported in 16 patients (47.1%). The overall response rate (ORR) was 17.4% in the full analysis set and 50.0% in the per-protocol set. Conclusions: SMT-NKs plus pembrolizumab resulted in no severe AEs directly related to the drug combination. The combination therapy also exerted antitumor activity with improved efficacy compared to the recent monotherapy with pembrolizumab in patients with advanced biliary tract cancer.

Dysregulation of immunity in COVID-19 and SLE

The immune response plays a crucial role in preventing diseases, such as infections. There are two types of immune responses, specific and innate immunity, each of which consists of two components: cellular immunity and humoral immunity. Dysfunction in any immune system component increases the risk of developing certain diseases. Systemic lupus erythematosus (SLE), an autoimmune disease in the human body, develops an immune response against its own components. In these patients, due to underlying immune system disorders and receipt of immunosuppressive drugs, the susceptibility to infections is higher than in the general population and is the single largest cause of mortality in this group. COVID-19 infection, which first appeared in late 2019, has caused several concerns in patients with SLE. However, there is no strong proof of additional risk of developing COVID-19 in patients with SLE, and in some cases, studies have shown less severity of the disease in these individuals. This review paper discusses the immune disorders in SLE and COVID-19.

KIR- Ligand Interactions in Hypertensive Disorders in Pregnancy

Hypothesis

The activity of natural killer (NK) cells is considered an important factor for the tolerance of the fetus during pregnancy. The complications of pregnancy, such as hypertensive disorders (HDP), may be therefore associated with this immune compartment.

Methods

The current study included 41 pregnant women diagnosed with HDPs (Gestational Hypertension; GH or Preeclampsia; PE) and 21 healthy women. All the patients were under continuous obstetric care during the pregnancy and labour. The number of mother-child mismatches within killer immunoglobulin-like receptors (KIRs), their ligands [MM], and missing KIR ligands [MSLs] was assessed. KIRs and their ligands were assessed with Next Generation Sequencing (NGS) and Polymerase Chain Reaction Sequence-Specific Oligonucleotide (PCR-SSO) typing. The subsets of NK cells were assessed with multicolor flow cytometry and correlated to the number of MSLs.

Results

The number of MSLs was significantly higher in HDP patients when compared to healthy non-complicated pregnancy patients. Some MSLs, such as those with 2DS2 activating KIR, were present only in HDP patients. The percentage of CD56+CD16-CD94+ NK cells and CD56+CD16-CD279+ NK cells correlated with the number of MSLs with inhibiting KIRs only in healthy patients. In HDP patients, there was a correlation between the percentage of CD56-CD16+CD69+ NK cells and the number of MSLs with inhibiting and activating KIRs. As compared to the healthy group, the percentage of CD56+CD16-CD279+ NK cells and CD56-CD16+CD279+ NK cells were lower in HDP patients. HDP patients were also characterized by a higher percentage of CD56+CD16+perforin+ NK cells than their healthy counterparts.

Conclusions

Patients with HDP were characterized by a higher number of MSLs within the KIRs receptors. It seemed that the number of MSLs in the healthy group was balanced by various receptors, such as CD94 or inhibitory CD279, expressed on NK cells. Conversely, in HDP patients the number of MSLs was associated with the activation detected as the increased level of CD69+ NK cells.

Comprehensive phenotyping of circulating immune cell subsets in people living with HIV

Systemic chronic inflammation and immune dysfunction are recognized as drivers of the development of non-AIDS related comorbidities (NARCs) in people living with HIV (PLHIV). In order to lower the risk of NARCs, it is critical to elucidate what is the contribution of alterations in the composition and function of circulating immune cells to NARCs-related pathogenesis. Findings from previous immunophenotyping studies in PLHIV are highly heterogeneous and it is not fully understood to what extent phenotypic changes on immune cells play a role in the dysregulated inflammatory response observed. In this study, three flow cytometry panels were designed and standardized to phenotypically and functionally identify the main circulating immune cell subsets in PLHIV. To reduce variability, up to 10 markers out of the approximately 20 markers in each panel were used in a custom dry format DURA Innovations (LUCID product line). Intra-assay precision tests performed for the selected cell subsets showed that the three panels had a %CV below 18% for percent of positive cells and the MFI (mean fluorescent intensity) of lineage markers. Our reported pipeline for immunophenotypic analysis facilitated the discrimination of 1153 cell populations, providing an integrated overview of circulating innate and adaptative immune cells as well as the cells' functional status in terms of activation, exhaustion, and maturation. When combined with unsupervised computational techniques, this standardized immunophenotyping approach may support the discovery of novel phenotypes with clinical relevance in NARCs and demonstrate future utility in other immune-mediated diseases.

Prostate Cancer Survivors Present Long-Term, Residual Systemic Immune Alterations

Simple Summary

The development of cancer is very often accompanied by systemic immune alterations which can be further aggravated by major anti-cancer therapies. However, there is very little known about how long these alterations persist in patients successfully cured of cancer. The aim of our work was to investigate how cancer and radiotherapy as major anti-cancer treatment modalities impact the immune system long after the successful treatment of a tumor. We investigated prostate cancer patients treated with a special form of radiotherapy (low-dose rate brachytherapy) often used for the treatment of prostate cancer and followed a wide range of immune parameters at regular intervals up to 3 years after the start of the treatment. Our results showed that some immune alterations did not recover after the treatment of the disease, on the contrary, they persisted, and in some cases got even worse. Further studies are needed to explain the causes and the potential long-term consequences of these alterations.

Abstract

Background: The development of cancer and anti-tumor therapies can lead to systemic immune alterations but little is known about how long immune dysfunction persists in cancer survivors. Methods: We followed changes in the cellular immune parameters of prostate cancer patients with good prognostic criteria treated with low dose rate brachytherapy before and up to 3 years after the initiation of therapy. Results: Patients before therapy had a reduced CD4+ T cell pool and increased regulatory T cell fraction and these alterations persisted or got amplified during the 36-month follow-up. A significant decrease in the total NK cell number and a redistribution of the circulating NK cells in favor of a less functional anergic subpopulation was seen in patients before therapy but tumor regression led to the regeneration of the NK cell pool and functional integrity. The fraction of lymphoid DCs was increased in patients both before therapy and throughout the whole follow-up. Increased PDGF-AA, BB, CCL5 and CXCL5 levels were measured in patients before treatment but protein levels rapidly normalized. Conclusions: while NK cell dysfunction recovered, long-term, residual alterations persisted in the adaptive and partly in the innate immune system.

Bispecific Antibody-Based Immune-Cell Engagers and Their Emerging Therapeutic Targets in Cancer Immunotherapy

Cancer is the second leading cause of death worldwide after cardiovascular diseases. Harnessing the power of immune cells is a promising strategy to improve the antitumor effect of cancer immunotherapy. Recent progress in recombinant DNA technology and antibody engineering has ushered in a new era of bispecific antibody (bsAb)-based immune-cell engagers (ICEs), including T- and natural-killer-cell engagers. Since the first approval of blinatumomab by the United States Food and Drug Administration (US FDA), various bsAb-based ICEs have been developed for the effective treatment of patients with cancer. Simultaneously, several potential therapeutic targets of bsAb-based ICEs have been identified in various cancers. Therefore, this review focused on not only highlighting the action mechanism, design and structure, and status of bsAb-based ICEs in clinical development and their approval by the US FDA for human malignancy treatment, but also on summarizing the currently known and emerging therapeutic targets in cancer. This review provides insights into practical considerations for developing next-generation ICEs.

Off-target effects of bacillus Calmette-Guérin vaccination on immune responses to SARS-CoV-2: implications for protection against severe COVID-19

Background and objectives

Because of its beneficial off‐target effects against non‐mycobacterial infectious diseases, bacillus Calmette–Guérin (BCG) vaccination might be an accessible early intervention to boost protection against novel pathogens. Multiple epidemiological studies and randomised controlled trials (RCTs) are investigating the protective effect of BCG against coronavirus disease 2019 (COVID‐19). Using samples from participants in a placebo‐controlled RCT aiming to determine whether BCG vaccination reduces the incidence and severity of COVID‐19, we investigated the immunomodulatory effects of BCG on in vitro immune responses to SARS‐CoV‐2.

Methods

This study used peripheral blood taken from participants in the multicentre RCT and BCG vaccination to reduce the impact of COVID‐19 on healthcare workers (BRACE trial). The whole blood taken from BRACE trial participants was stimulated with γ‐irradiated SARS‐CoV‐2‐infected or mock‐infected Vero cell supernatant. Cytokine responses were measured by multiplex cytokine analysis, and single‐cell immunophenotyping was made by flow cytometry.

Results

BCG vaccination, but not placebo vaccination, reduced SARS‐CoV‐2‐induced secretion of cytokines known to be associated with severe COVID‐19, including IL‐6, TNF‐α and IL‐10. In addition, BCG vaccination promoted an effector memory phenotype in both CD4⁺ and CD8⁺ T cells, and an activation of eosinophils in response to SARS‐CoV‐2.

Conclusions

The immunomodulatory signature of BCG’s off‐target effects on SARS‐CoV‐2 is consistent with a protective immune response against severe COVID‐19.

Analysis of the expression and prognosis for leukocyte immunoglobulin-like receptor subfamily B in human liver cancer

Background

Leukocyte immunoglobulin-like receptor subfamily B (LILRB), including 5 subtypes, is a group of inhibitory receptors in the immune system. The LILRB family is known to be involved in the tumor progression of various cancer types, especially liver cancer. However, the expression patterns and prognostic values of LILRB family members in liver cancer tissues remain unclear.

Methods

We used the Oncomine database, GEPIA database, Kaplan–Meier Plotter, Timer, and TISIDB to assess the expression and prognostic value of the LILRB family in liver cancer patients. We also verified the expression of the LILRB family in tumor tissues and tumor-free liver tissues at the protein level by using immunohistochemistry. The STRING website was used to explore the interaction between the LILRB family and their related genes. The DAVID database was used to perform the gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. Flow cytometry was used to assess the infiltrated NK cells in liver cancer tissues.

Results

Our study revealed that the mRNA expression of LILRB1, LILRB2, LILRB3, and LILRB5 was downregulated, while compared with normal tissues, the mRNA expression of LILRB4 was upregulated in liver cancer tissues. Survival analysis revealed that LILRB2 and LILRB5 mRNA expression levels were significantly positively associated with overall survival (OS) and disease-free survival (DSS) and that the mRNA expression of all LILRB family members was significantly positively correlated with recurrence-free survival (RFS) and progression-free survival (PFS). Next, we further found that the mRNA expression of all LILRB family members was significantly associated with the infiltration of B cells, CD8⁺ T cells, CD4⁺ T cells, macrophages, neutrophils, and dendritic cells in liver cancer. Finally, GO and KEGG analyses found that the LILRB family and its related genes were involved in antigen processing and presentation and natural killer cell-mediated cytotoxicity pathways.

Conclusions

Our study suggested that LILRB family expression was associated with the prognosis of liver cancer patients and infiltrated immune cells. The LILRB family might be involved in antigen processing and presentation and natural killer cell-mediated cytotoxicity pathways.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12957-022-02562-w.

Engineered NK Cells Against Cancer and Their Potential Applications Beyond

Cell therapy is an innovative therapeutic concept where viable cells are implanted, infused, or grafted into a patient to treat impaired or malignant tissues. The term was first introduced circa the 19th century and has since resulted in multiple breakthroughs in different fields of medicine, such as neurology, cardiology, and oncology. Lately, cell and gene therapy are merging to provide cell products with additional or enhanced properties. In this context, adoptive transfer of genetically modified cytotoxic lymphocytes has emerged as a novel treatment option for cancer patients. To this day, five cell therapy products have been FDA approved, four of which for CD19-positive malignancies and one for B-cell maturation antigen (BCMA)-positive malignancies. These are personalized immunotherapies where patient T cells are engineered to express chimeric antigen receptors (CARs) with the aim to redirect the cells against tumor-specific antigens. CAR-T cell therapies show impressive objective response rates in clinical trials that, in certain instances, may reach up to 80%. However, the life-threatening side effects associated with T cell toxicity and the manufacturing difficulties of developing personalized therapies hamper their widespread use. Recent literature suggests that Natural Killer (NK) cells, may provide a safer alternative and an 'off-the-shelf' treatment option thanks to their potent antitumor properties and relatively short lifespan. Here, we will discuss the potential of NK cells in CAR-based therapies focusing on the applications of CAR-NK cells in cancer therapy and beyond.

Phenotypic and Functional Plasticity of CXCR6+ Peripheral Blood NK Cells

Human NK cells are comprised of phenotypic subsets, whose potentially unique functions remain largely unexplored. C-X-C-motif-chemokine-receptor-6 (CXCR6)+ NK cells have been identified as phenotypically immature tissue-resident NK cells in mice and humans. A small fraction of peripheral blood (PB)-NK cells also expresses CXCR6. However, prior reports about their phenotypic and functional plasticity are conflicting. In this study, we isolated, expanded, and phenotypically and functionally evaluated CXCR6+ and CXCR6– PB-NK cells, and contrasted results to bulk liver and spleen NK cells. We found that CXCR6+ and CXCR6– PB-NK cells preserved their distinct phenotypic profiles throughout 14 days of in vitro expansion (“day 14”), after which phenotypically immature CXCR6+ PB-NK cells became functionally equivalent to CXCR6– PB-NK cells. Despite a consistent reduction in CD16 expression and enhanced expression of the transcription factor Eomesodermin (Eomes), day 14 CXCR6+ PB-NK cells had superior antibody-dependent cellular cytotoxicity (ADCC) compared to CXCR6– PB-NK cells. Further, bulk liver NK cells responded to IL-15, but not IL-2 stimulation, with STAT-5 phosphorylation. In contrast, bulk splenic and PB-NK cells robustly responded to both cytokines. Our findings may allow for the selection of superior NK cell subsets for infusion products increasingly used to treat human diseases.

A Hot Topic: Cancer Immunotherapy and Natural Killer Cells

Despite significant progress in recent years, the therapeutic approach of the multiple different forms of human cancer often remains a challenge. Besides the well-established cancer surgery, radiotherapy and chemotherapy, immunotherapeutic strategies gain more and more attention, and some of them have already been successfully introduced into the clinic. Among these, immunotherapy based on natural killer (NK) cells is considered as one of the most promising options. In the present review, we will expose the different possibilities NK cells offer in this context, compare data about the theoretical background and mechanism(s) of action, report some results of clinical trials and identify several very recent trends. The pharmaceutical industry is quite interested in NK cell immunotherapy, which will benefit the speed of progress in the field.

Modulation of intrinsic inhibitory checkpoints using nano-carriers to unleash NK cell activity

Natural killer (NK) cells provide a powerful weapon mediating immune defense against viral infections, tumor growth, and metastatic spread. NK cells demonstrate great potential for cancer immunotherapy; they can rapidly and directly kill cancer cells in the absence of MHC-dependent antigen presentation and can initiate a robust immune response in the tumor microenvironment (TME). Nevertheless, current NK cell-based immunotherapies have several drawbacks, such as the requirement for ex vivo expansion of modified NK cells, and low transduction efficiency. Furthermore, to date, no clinical trial has demonstrated a significant benefit for NK-based therapies in patients with advanced solid tumors, mainly due to the suppressive TME. To overcome current obstacles in NK cell-based immunotherapies, we describe here a non-viral lipid nanoparticle-based delivery system that encapsulates small interfering RNAs (siRNAs) to gene silence the key intrinsic inhibitory NK cell molecules, SHP-1, Cbl-b, and c-Cbl. The nanoparticles (NPs) target NK cells in vivo, silence inhibitory checkpoint signaling molecules, and unleash NK cell activity to eliminate tumors. Thus, the novel NP-based system developed here may serve as a powerful tool for future NK cell-based therapeutic approaches.

A high-dimensional cytometry atlas of peripheral blood over the human life span

Age can profoundly affect susceptibility to a broad range of human diseases. Children are more susceptible to some infectious diseases such as diphtheria and pertussis, while in others, such as coronavirus disease 2019 and hepatitis A, they are more protected compared with adults. One explanation is that the composition of the immune system is a major contributing factor to disease susceptibility and severity. While most studies of the human immune system have focused on adults, how the immune system changes after birth remains poorly understood. Here, using high-dimensional spectral flow cytometry and computational methods for data integration, we analyzed more than 50 populations of immune cells in the peripheral blood, generating an immune cell atlas that defines the healthy human immune system from birth up to 75 years of age. We focused our efforts on children under 18 years old, revealing major changes in immune cell populations after birth and in children of schooling age. Specifically, CD4⁺ T effector memory cells, Vδ2⁺ gamma delta (γδ)T cells, memory B cells, plasmablasts, CD11c⁺ B cells and CD16⁺ CD56^bright natural killer (NK) cells peaked in children aged 5-9 years old, whereas frequencies of T helper 1, T helper 17, dendritic cells and CD16⁺ CD57⁺ CD56^dim NK cells were highest in older children (10-18 years old). The frequency of mucosal-associated invariant T cells was low in the first several years of life and highest in adults between 19 and 30 years old. Late adulthood was associated with fewer mucosal-associated invariant T cells and Vδ2⁺ γδ T cells but with increased frequencies of memory subsets of B cells, CD4⁺ and CD8⁺ T cells and CD57⁺ NK cells. This human immune cell atlas provides a critical resource to understand changes to the immune system during life and provides a reference for investigating the immune system in the context of human disease. This work may also help guide future therapies that target specific populations of immune cells to protect at-risk populations.

Expansion of CD56dimCD16neg NK Cell Subset and Increased Inhibitory KIRs in Hospitalized COVID-19 Patients

Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV-2) infection induces elevated levels of inflammatory cytokines, which are mainly produced by the innate response to the virus. The role of NK cells, which are potent producers of IFN-γ and cytotoxicity, has not been sufficiently studied in the setting of SARS-CoV-2 infection. We confirmed a different distribution of NK cell subsets in hospitalized COVID-19 patients despite their NK cell deficiency. The impairment of this innate defense is mainly focused on the cytotoxic capacity of the CD56^dim NK cells. On the one hand, we found an expansion of the CD56^dimCD16^neg NK subset, lower cytotoxic capacities, and high frequencies of inhibitory 2DL1 and 2DL1/S1 KIR receptors in COVID-19 patients. On the other hand, the depletion of CD56^dimCD16^dim/bright NK cell subsets, high cytotoxic capacities, and high frequencies of inhibitory 2DL1 KIR receptors were found in COVID-19 patients. In contrast, no differences in the distribution of CD56^bright NK cell subsets were found in this study. These alterations in the distribution and phenotype of NK cells might enhance the impairment of this crucial innate line of defense during COVID-19 infection.

PD-1, CTLA-4, LAG-3, and TIGIT: The roles of immune checkpoint receptors on the regulation of human NK cell phenotype and functions

The roles of immune checkpoint receptors were defined in many cancers and autoimmune diseases, while there is limited information on their functional roles in the NK cells of healthy individuals. Immune checkpoint receptor expression of NK cell subsets and their association with NK cell functions (cytotoxic capacity and cytokine production) in healthy population were investigated. PD-1, CTLA-4, LAG-3 and TIGIT expression of peripheral blood NK cells, cytokine levels (TNF-α, IFN-γ, IL-10) and cytotoxic functions (granzyme A, perforin, CD107a; with/without K562 target cell stimulation) were evaluated by flow cytometry. CD56^dimCD16^dim NK cells had the highest expression of TIGIT, while CD56^dimCD16^- NK cells had highest expression of PD-1, CTLA-4 and LAG-3. PD-1⁺ NK cells, CTLA-4⁺ NK cells and LAG-3⁺ NK cells had increased amount of IL-10 however, reduced IFN-γ and TNF-α levels. Cytotoxic granule expressions (perforin and granzyme A) were reduced in PD-1⁺ NK cells, CTLA-4⁺ NK cells and LAG-3⁺ NK cells. However, TIGIT expression did not alter perforin and granzyme A expressions. Degranulation capacity was reduced in three groups of NK cells (PD-1⁺ or LAG-3⁺ or TIGIT⁺). TIGIT⁺ NK cells responded strongly to target cell stimulation, while NK cells in the other groups (PD-1⁺ or CTLA-4⁺ or LAG-3⁺) were resistant. PD-1⁺ NK cells, CTLA-4⁺ NK cells and LAG-3⁺ NK cells had a regulatory phenotype, impaired cytotoxic functions, and response to target cell stimulation. In contrast, TIGIT⁺ NK cells had strong baseline cytotoxic activity that further increased in response to target cell stimulation.

Combined Blockade of TIGIT and CD39 or A2AR Enhances NK-92 Cell-Mediated Cytotoxicity in AML

This study aimed to characterize different natural killer (NK) cell phenotypes on bone marrow and peripheral blood cells from acute myeloid leukemia (AML) patients and healthy donors (HDs). Our data show that CD56^dimCD16⁻ and CD56^brightCD16⁻ NK cells represent the predominant NK cell subpopulations in AML, while the CD56^dimCD16⁺ NK cells are significantly reduced compared to HDs. Moreover, TIGIT⁺ and PVRIG⁺ cells cluster on the CD56^dimCD16⁺ subset whereas CD39⁺ and CD38⁺ cells do so on CD56^brightCD16⁻ NK cells in AML. Furthermore, functional effects of (co-)blockade of TIGIT and CD39 or A2AR on NK cell functionality were analyzed. These experiments revealed that the single blockade of the TIGIT receptor results in an increased NK-92 cell-mediated killing of AML cells in vitro. Combined targeting of CD39 or A2AR significantly augments the anti-TIGIT-mediated lysis of AML cells. Our data indicate that distinct NK cell subsets in AML exhibit different immunosuppressive patterns (via the TIGIT/PVRIG receptors and the purinergic pathway). In summary, we conclude that TIGIT, CD39, and A2AR constitute relevant inhibitory checkpoints of NK cells in AML patients. A combinatorial blockade synergistically strengthens NK-92 cell-mediated cytotoxicity. As inhibitors of TIGIT, CD39, and A2AR are clinically available, studies on their combined use could be conducted in the near future.