CD56bright natural killer cell subsets: characterization of distinct functional responses to interleukin-2 and the c-kit ligand

A differential diagnosis method for systemic CAEBV and the prospect of EBV-related immune cell markers via flow cytometry

Chronic active Epstein-Barr virus (CAEBV) infection of the T-cell or Natural killer (NK)-cell type, systemic form (systemic CAEBV or sCAEBV) was defined by the WHO in 2017 as an EBV-related lymphoproliferative disorder and is listed as an EBV-positive T-cell and NK-cell proliferation. The clinical manifestations and prognoses are heterogeneous. This makes systemic CAEBV indistinguishable from other EBV-positive T-cell and NK-cell proliferations. Early diagnosis of systemic CAEBV and early hematopoietic stem cell transplantation can improve patient prognosis. At present, the diagnosis of systemic CAEBV relies mainly on age, clinical manifestations, and cell lineage, incurring missed diagnosis, misdiagnosis, long diagnosis time, and inability to identify high-risk systemic CAEBV early. The diagnostic methods for systemic CAEBV are complicated and lack systematic description. The recent development of diagnostic procedures, including molecular biological and immunological techniques such as flow cytometry, has provided us with the ability to better understand the proliferation of other EBV-positive T cells and NK cells, but there is no definitive review of their value in diagnosing systemic CAEBV. This article summarizes the recent progress in systemic CAEBV differential diagnosis and the prospects of flow cytometry.

The immunomodulatory effects of cannabidiol on Hsp70-activated NK cells and tumor target cells

BACKGROUND

Cannabidiol (CBD), the major non-psychoactive component of cannabis, exhibits anti-inflammatory properties, but less is known about the immunomodulatory potential of CBD on activated natural killer (NK) cells and/or their targets. Many tumor cells present heat shock protein 70 (Hsp70) on their cell surface in a tumor-specific manner and although a membrane Hsp70 (mHsp70) positive phenotype serves as a target for Hsp70-activated NK cells, a high mHsp70 expression is associated with tumor aggressiveness. This study investigated the immuno-modulatory potential of CBD on NK cells stimulated with TKD Hsp70 peptide and IL-2 (TKD+IL-2) and also on HCT116 p53wt and HCT116 p53-/- colorectal cancer cells exhibiting high and low basal levels of mHsp70 expression.

RESULTS

Apart from an increase in the density of NTB-A and a reduced expression of LAMP-1, the expression of all other activatory NK cell receptors including NKp30, NKG2D and CD69 which are significantly up-regulated after stimulation with TKD+IL-2 remained unaffected after a co-treatment with CBD. However, the release of major pro-inflammatory cytokines by NK cells such as interferon-γ (IFN-γ) and the effector molecule granzyme B (GrzB) was significantly reduced upon CBD treatment. With respect to the tumor target cells, CBD significantly reduced the elevated expression of mHsp70 but had no effect on the low basal mHsp70 expression. Expression of other NK cell ligands such as MICA and MICB remained unaffected, and the NK cell ligands ULBP and B7-H6 were not expressed on these target cells. Consistent with the reduced mHsp70 expression, treatment of both effector and target cells with CBD reduced the killing of high mHsp70 expressing tumor cells by TKD+IL-2+CBD pre-treated NK cells but had no effect on the killing of low mHsp70 expressing tumor cells. Concomitantly, CBD treatment reduced the TKD+IL-2 induced increased release of IFN-γ, IL-4, TNF-α and GrzB, but CBD had no effect on the release of IFN-α when NK cells were co-incubated with tumor target cells.

CONCLUSION

Cannabidiol (CBD) may potentially diminish the anti-tumor effectiveness of TKD+IL-2 activated natural killer (NK) cells.

NK cell subsets and dysfunction during viral infection: a new avenue for therapeutics?

In the setting of viral challenge, natural killer (NK) cells play an important role as an early immune responder against infection. During this response, significant changes in the NK cell population occur, particularly in terms of their frequency, location, and subtype prevalence. In this review, changes in the NK cell repertoire associated with several pathogenic viral infections are summarized, with a particular focus placed on changes that contribute to NK cell dysregulation in these settings. This dysregulation, in turn, can contribute to host pathology either by causing NK cells to be hyperresponsive or hyporesponsive. Hyperresponsive NK cells mediate significant host cell death and contribute to generating a hyperinflammatory environment. Hyporesponsive NK cell populations shift toward exhaustion and often fail to limit viral pathogenesis, possibly enabling viral persistence. Several emerging therapeutic approaches aimed at addressing NK cell dysregulation have arisen in the last three decades in the setting of cancer and may prove to hold promise in treating viral diseases. However, the application of such therapeutics to treat viral infections remains critically underexplored. This review briefly explores several therapeutic approaches, including the administration of TGF-β inhibitors, immune checkpoint inhibitors, adoptive NK cell therapies, CAR NK cells, and NK cell engagers among other therapeutics.

A2AR limits IL-15-induced generation of CD39+ NK cells with high cytotoxicity

CD39-mediated inhibition of natural killer (NK) cell activity has been demonstrated, but the characteristics of CD39⁺ NK cells in humans are not known. We investigated the characteristics of human circulating CD39⁺ NK cells. In healthy donors, the proportion of circulating CD39⁺ NK cells in total NK cells was relatively low compared with that of CD39^- NK cells. Nonetheless, a higher proportion of CD39⁺ NK cells expressed CD107a. Similarly, a higher proportion of CD39⁺ NK cells expressed CD107a in patients with hepatitis B virus or patients with hepatocellular carcinoma. Stimulation with NK-sensitive K562 cells or interleukin (IL)-12/IL-18 activated CD39⁺ NK cells to express higher levels of CD107a, IFN-γ and TNF-α, relative to CD39^- NK cells. Importantly, IL-15 induced the generation of CD39⁺ NK cells. In contrast, A2A adenosine receptor (A2AR) ligation suppressed the generation of CD39⁺ NK cells by inhibiting IL-15 signaling. These data for the first time demonstrated that A2AR counteracts IL-15-induced generation of human CD39⁺ NK cells, which have a stronger cytotoxicity than CD39^- NK cells. IL-15-induced human CD39⁺ NK cells might be better choice for immunotherapy based on adoptive transfer of NK cells.

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.

Longitudinal Virological and Immunological Profile in a Case of Human Monkeypox Infection

In a male with severe proctitis, monkeypox virus DNA was detected in skin lesions, blood, the nasopharynx, and the rectum, underlying generalized viral spreading. Rectal involvement was still found when skin lesions disappeared. At this early stage, an increase of cytotoxic and activated T cells was observed, while a reduction in CD56dimCD57+ NK cells compared with recovery time point was observed.

Mucosal Immunity and the Gut-Microbiota-Brain-Axis in Neuroimmune Disease

Recent advances in next-generation sequencing (NGS) technologies have opened the door to a wellspring of information regarding the composition of the gut microbiota. Leveraging NGS technology, early metagenomic studies revealed that several diseases, such as Alzheimer's disease, Parkinson's disease, autism, and myalgic encephalomyelitis, are characterized by alterations in the diversity of gut-associated microbes. More recently, interest has shifted toward understanding how these microbes impact their host, with a special emphasis on their interactions with the brain. Such interactions typically occur either systemically, through the production of small molecules in the gut that are released into circulation, or through signaling via the vagus nerves which directly connect the enteric nervous system to the central nervous system. Collectively, this system of communication is now commonly referred to as the gut-microbiota-brain axis. While equally important, little attention has focused on the causes of the alterations in the composition of gut microbiota. Although several factors can contribute, mucosal immunity plays a significant role in shaping the microbiota in both healthy individuals and in association with several diseases. The purpose of this review is to provide a brief overview of the components of mucosal immunity that impact the gut microbiota and then discuss how altered immunological conditions may shape the gut microbiota and consequently affect neuroimmune diseases, using a select group of common neuroimmune diseases as examples.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (third edition)

The third edition of Flow Cytometry Guidelines provides the key aspects to consider when performing flow cytometry experiments and includes comprehensive sections describing phenotypes and functional assays of all major human and murine immune cell subsets. Notably, the Guidelines contain helpful tables highlighting phenotypes and key differences between human and murine cells. Another useful feature of this edition is the flow cytometry analysis of clinical samples with examples of flow cytometry applications in the context of autoimmune diseases, cancers as well as acute and chronic infectious diseases. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid. All sections are written and peer-reviewed by leading flow cytometry experts and immunologists, making this edition an essential and state-of-the-art handbook for basic and clinical researchers.

Defining the AHR-regulated transcriptome in NK cells reveals gene expression programs relevant to development and function

AHR directly regulates a wide range of genes in NK cells, including those involved in cell signaling, oxidative stress, and metabolism.

Knowing of the repertoire of genes regulated by AHR may help us better understand NK-cell dysfunction mediated by AHR ligands in cancer.

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that regulates cellular processes in cancer and immunity, including innate immune cell development and effector function. However, the transcriptional repertoire through which AHR mediates these effects remains largely unexplored. To elucidate the transcriptional elements directly regulated by AHR in natural killer (NK) cells, we performed RNA and chromatin immunoprecipitation sequencing on NK cells exposed to AHR agonist or antagonist. We show that mature peripheral blood NK cells lack AHR, but its expression is induced by Stat3 during interleukin-21–driven activation and proliferation, coincident with increased NCAM1 (CD56) expression resulting in a CD56^bright phenotype. Compared with control conditions, NK cells expanded in the presence of the AHR antagonist, StemRegenin-1, were unaffected in proliferation or cytotoxicity, had no increase in NCAM1 transcription, and maintained the CD56^dim phenotype. However, it showed altered expression of 1004 genes including those strongly associated with signaling pathways. In contrast, NK cells expanded in the presence of the AHR agonist, kynurenine, showed decreased cytotoxicity and altered expression of 97 genes including those strongly associated with oxidative stress and cellular metabolism. By overlaying these differentially expressed genes with AHR chromatin binding, we identified 160 genes directly regulated by AHR, including hallmark AHR targets AHRR and CYP1B1 and known regulators of phenotype, development, metabolism, and function such as NCAM1, KIT, NQO1, and TXN. In summary, we define the AHR transcriptome in NK cells, propose a model of AHR and Stat3 coregulation, and identify potential pathways that may be targeted to overcome AHR-mediated immune suppression.

NK and T Cell Immunological Signatures in Hospitalized Patients with COVID-19

Severe acute respiratory syndrome caused by coronavirus 2 emerged in Wuhan (China) in December 2019 and has severely challenged the human population. NK and T cells are involved in the progression of COVID-19 infection through the ability of NK cells to modulate T-cell responses, and by the stimulation of cytokine release. No detailed investigation of the NK cell landscape in clinical SARS-CoV-2 infection has yet been reported. A total of 35 COVID-19 hospitalised patients were stratified for clinical severity and 17 healthy subjects were enrolled. NK cell subsets and T cell subsets were analysed with flow cytometry. Serum cytokines were detected with a bead-based multiplex assay. Fewer CD56dimCD16brightNKG2A+NK cells and a parallel increase in the CD56+CD69+NK, CD56+PD-1+NK, CD56+NKp44+NK subset were reported in COVID-19 than HC. A significantly higher adaptive/memory-like NK cell frequency in patients with severe disease than in those with mild and moderate phenotypes were reported. Moreover, adaptive/memory-like NK cell frequencies were significantly higher in patients who died than in survivors. Severe COVID-19 patients showed higher serum concentrations of IL-6 than mild and control groups. Direct correlation emerged for IL-6 and adaptive/memory-like NK. All these findings provide new insights into the immune response of patients with COVID-19. In particular, they demonstrate activation of NK through overexpression of CD69 and CD25 and show that PD-1 inhibitory signalling maintains an exhausted phenotype in NK cells. These results suggest that adaptive/memory-like NK cells could be the basis of promising targeted therapy for future viral infections.

Geriatrics and COVID-19

Since December 2019, a novel coronavirus called severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has begun to infect people. The virus first occurred in Wuhan, China, but the whole world is now struggling with the pandemic. Over 13 million confirmed cases and 571,000 deaths have been reported so far, and this number is growing. Older people, who constitute a notable proportion of the world population, are at an increased risk of infection because of altered immunity and chronic comorbidities. Thus, appropriate health care is necessary to control fatalities and spread of the disease in this specific population. The chapter provides an overview of diagnostic methods, laboratory and imaging findings, clinical features, and management of COVID-19 in aged people. Possible mechanisms behind the behavior of SARS-CoV-2 in the elderly include immunosenescence and related impaired antiviral immunity, mature immunity and related hyper-inflammatory responses, comorbidities and their effects on the functioning of critical organs/systems, and the altered expression of angiotensin-converting enzyme 2 (ACE2) that acts as an entry receptor for SARS-CoV-2. This evidence defines the herding behavior of COVID-19 in relation to ACE2 under the influence of immune dysregulation. Then, identifying the immunogenetic factors that affect the disease susceptibility and severity and as well as key inflammatory pathways that have the potential to serve as therapeutic targets needs to remain an active area of research.

Natural Killer Cell Subpopulations and Inhibitory Receptor Dynamics in Myelodysplastic Syndromes and Acute Myeloid Leukemia

Natural killer (NK) cells are key innate immunity effectors that play a major role in malignant cell destruction. Based on expression patterns of CD16, CD56, CD57, and CD94, three distinct NK cell maturation stages have been described, which differ in terms of cytokine secretion, tissue migration, and the ability to kill target cells. Our study addressed NK cell maturation in bone marrow under three conditions: a normal developmental environment, during pre-leukemic state (myelodysplastic syndrome, MDS), and during leukemic transformation (acute myeloblastic leukemia, AML). In this study, we used a new tool to perform multicolor flow cytometry data analysis, based on principal component analysis, which allowed the unsupervised, accurate discrimination of immature, mature, and hypermature NK subpopulations. An impaired NK/T cell distribution was observed in the MDS bone marrow microenvironment compared with the normal and AML settings, and a phenotypic shift from the mature to the immature state was observed in NK cells under both the MDS and AML conditions. Furthermore, an impaired NK cell antitumor response, resulting in changes in NK cell receptor expression (CD159a, CD158a, CD158b, and CD158e1), was observed under MDS and AML conditions compared with the normal condition. The results of this study provide evidence for the failure of this arm of the immune response during the pathogenesis of myeloid malignancies. NK cell subpopulations display a heterogeneous and discordant dynamic on the spectrum between normal and pathological conditions. MDS does not appear to be a simple, intermediate stage but rather serves as a decisive step for the mounting of an efficient or ineffective immune response, leading to either the removal of the tumor cells or to malignancy.

Elevated Exhaustion Levels of NK and CD8+ T Cells as Indicators for Progression and Prognosis of COVID-19 Disease

Background

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) induced Coronavirus Disease 2019 (COVID-19) has posed a global threat to public health. The immune system is crucial in defending and eliminating the virus and infected cells. However, immune dysregulation may result in the rapid progression of COVID-19. Here, we evaluated the subsets, phenotypic and functional characteristics of natural killer (NK) and T cells in patients with COVID-19 and their associations with disease severity.

Methods

Demographic and clinical data of COVID-19 patients enrolled in Wuhan Union Hospital from February 25 to February 27, 2020, were collected and analyzed. The phenotypic and functional characteristics of NK cells and T cells subsets in circulating blood and serum levels of cytokines were analyzed via flow cytometry. Then the LASSO logistic regression model was employed to predict risk factors for the severity of COVID-19.

Results

The counts and percentages of NK cells, CD4⁺ T cells, CD8⁺ T cells and NKT cells were significantly reduced in patients with severe symptoms. The cytotoxic CD3^-CD56^dimCD16⁺ cell population significantly decreased, while the CD3^-CD56^dimCD16^- part significantly increased in severe COVID-19 patients. More importantly, elevated expression of regulatory molecules, such as CD244 and programmed death-1 (PD-1), on NK cells and T cells, as well as decreased serum cytotoxic effector molecules including perforin and granzyme A, were detected in patients with COVID-19. The serum IL-6, IL-10, and TNF-α were significantly increased in severe patients. Moreover, the CD3^-CD56^dimCD16^- cells were screened out as an influential factor in severe cases by LASSO logistic regression.

Conclusions

The functional exhaustion and other subset alteration of NK and T cells may contribute to the progression and improve the prognosis of COVID-19. Surveillance of lymphocyte subsets may in the future enable early screening for signs of critical illness and understanding the pathogenesis of this disease.

Tissue-Resident NK Cells: Development, Maturation, and Clinical Relevance

Natural killer (NK) cells belong to type 1 innate lymphoid cells (ILC1) and are essential in killing infected or transformed cells. NK cells mediate their effector functions using non-clonotypic germ-line-encoded activation receptors. The utilization of non-polymorphic and conserved activating receptors promoted the conceptual dogma that NK cells are homogeneous with limited but focused immune functions. However, emerging studies reveal that NK cells are highly heterogeneous with divergent immune functions. A distinct combination of several activation and inhibitory receptors form a diverse array of NK cell subsets in both humans and mice. Importantly, one of the central factors that determine NK cell heterogeneity and their divergent functions is their tissue residency. Decades of studies provided strong support that NK cells develop in the bone marrow. However, evolving evidence supports the notion that NK cells also develop and differentiate in tissues. Here, we summarize the molecular basis, phenotypic signatures, and functions of tissue-resident NK cells and compare them with conventional NK cells.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (second edition)

These guidelines are a consensus work of a considerable number of members of the immunology and flow cytometry community. They provide the theory and key practical aspects of flow cytometry enabling immunologists to avoid the common errors that often undermine immunological data. Notably, there are comprehensive sections of all major immune cell types with helpful Tables detailing phenotypes in murine and human cells. The latest flow cytometry techniques and applications are also described, featuring examples of the data that can be generated and, importantly, how the data can be analysed. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid, all written and peer-reviewed by leading experts in the field, making this an essential research companion.

Diversification of human NK cells: Lessons from deep profiling

NK cells are innate lymphocytes with important roles in immunoregulation, immunosurveillance, and cytokine production. Originally defined on the functional basis of their "natural" ability to lyse tumor targets and thought to be a relatively homogeneous group of lymphocytes, NK cells possess a remarkable degree of phenotypic and functional diversity due to the combinatorial expression of an array of activating and inhibitory receptors. Diversification of NK cells is multifaceted: mechanisms of NK cell education that promote self-tolerance result in a heterogeneous repertoire that further diversifies upon encounters with viral pathogens. Here, we review the genetic, developmental, and environmental sources of NK cell diversity with a particular focus on deep profiling and single-cell technologies that will enable a more thorough and accurate dissection of this intricate and poorly understood lymphocyte lineage.

Alterations of oncogenes expression in NK cells in patients with cancer

INTRODUCTION

C-kit/SCF signaling plays a key role in regulating NK cell homeostasis, maturation, proliferation, and cytotoxicity. C-kit-deficiency in NK cells results in significant reduction of their number, suggesting an imperative role for c-kit signaling in NK cell biology. We have recently showed that human NK cells express not only c-kit-receptor, but also both membrane-bound and soluble forms of c-kit ligand-Stem cell factor. The goal of this study was to characterize the c-kit/SCF autocrine loop in peripheral blood NK cells obtained from patients with cancer.

METHODS

Using Smart Flare and qRT-PCR, we have characterized expression of c-kit and two forms of SCF in patients' NK cells and correlated these results with the expression of c-myc and STAT3.

RESULTS

Our results demonstrated that the expression of proto-oncogenes c-myc and c-kit was significantly decreased in NK cells from all cancer patients. Expression of membrane-bound SCF in NK cells correlated with the presence of remote metastases.

CONCLUSIONS

We suggest that the abnormal signaling and expression of c-kit/SCF, c-myc, and STAT3 in NK cells is responsible for the defect in their cytolytic activity in cancer and these defects at the gene expression level may be the cause rather than the result of tumor progression.

Emerging insights into natural killer cells in human peripheral tissues

Natural killer (NK) cells have long been considered to be a homogenous population of innate lymphocytes with limited phenotypic and functional diversity. However, recent findings have revealed that these cells comprise a large number of distinct populations with diverse characteristics. Some of these characteristics may relate to their developmental origin, and others represent differences in differentiation that are influenced by factors such as tissue localization and imprints by viral infections. In this Review, we provide a comprehensive overview of the emerging knowledge about the development, differentiation and function of human NK cell populations, with a particular focus on NK cells in peripheral tissues.

Siglec-7 Defines a Highly Functional Natural Killer Cell Subset and Inhibits Cell-Mediated Activities

Sialic acid-binding immunoglobulin-like lectin-7 (Siglec-7) is an inhibitory receptor expressed on natural killer (NK) cells. In this study, we investigated the relationship between Siglec-7 expression and NK cell functions. Siglec-7 was highly expressed on NK cells and was preferentially expressed by mature NK cells from peripheral blood of healthy adults. Siglec-7(+) NK cells displayed higher levels of activating receptors CD38, CD16, DNAM1, NKp30 and NKp46, but lower levels of inhibitory receptors such as NKG2A and CD158b, compared with Siglec-7(-) NK cells. Functional tests showed that Siglec-7(+) NK cells displayed more CD107a degranulation and IFN-γ production than Siglec-7(-) NK cells. Siglec-7 inhibited NK cell functions when interacting with specific antibodies. These data suggest that Siglec-7 defines a highly functional NK cell subset and suppresses NK cell-mediated functions when cross-linked with specific antibodies.

The Development and Diversity of ILCs, NK Cells and Their Relevance in Health and Diseases

Next to T and B cells, natural killer (NK) cells are the third largest lymphocyte population. They are recently re-categorized as innate lymphocytes (ILCs), which also include ILC1, ILC2, ILC3, and the lymphoid tissue inducer (LTi) cells. Both NK cells and ILC1 cells are designated as group 1 ILCs because they secrete interferon-γ (IFN-γ) and tumor necrosis factor (TNF). However, in contrast to ILC1 and all other ILCs, NK cells possess potent cytolytic functions that resemble cytotoxic T lymphocytes (CTL). In addition, NK cells express, in a stochastic manner, an array of germ line-encoded activating and inhibitory receptors that recognize the polymorphic regions of major histocompatibility class I (MHC-I) molecules and self-proteins. Recognition of self renders NK cell tolerance to self-healthy tissues, but fail to recognize self ('missing-self') leads to activation to neoplastic transformation and infections of certain viruses. In this chapter, we will summarize the development of NK cells in the context of ILCs, describe the diversity of phenotype and function in blood and tissues, and discuss their involvement in health and diseases in humans.

Development of a Modular Assay for Detailed Immunophenotyping of Peripheral Human Whole Blood Samples by Multicolor Flow Cytometry

The monitoring of immune cells gained great significance in prognosis and prediction of therapy responses. For analyzing blood samples, the multicolor flow cytometry has become the method of choice as it combines high specificity on single cell level with multiple parameters and high throughput. Here, we present a modular assay for the detailed immunophenotyping of blood (DIoB) that was optimized for an easy and direct application in whole blood samples. The DIoB assay characterizes 34 immune cell subsets that circulate the peripheral blood including all major immune cells such as T cells, B cells, natural killer (NK) cells, monocytes, dendritic cells (DCs), neutrophils, eosinophils, and basophils. In addition, it evaluates their functional state and a few non-leukocytes that also have been associated with the outcome of cancer therapy. This DIoB assay allows a longitudinal and close-meshed monitoring of a detailed immune status in patients requiring only 2.0 mL of peripheral blood and it is not restricted to peripheral blood mononuclear cells. It is currently applied for the immune monitoring of patients with glioblastoma multiforme (IMMO-GLIO-01 trial, NCT02022384), pancreatic cancer (CONKO-007 trial, NCT01827553), and head and neck cancer (DIREKHT trial, NCT02528955) and might pave the way for immune biomarker identification for prediction and prognosis of therapy outcome.

Cord Blood as a Source of Natural Killer Cells

Cord blood (CB) offers several unique advantages as a graft source for hematopoietic stem cell transplantation (HSCT). The risk of relapse and graft vs. host disease after cord blood transplantation (CBT) is lower than what is typically observed after other graft sources with a similar degree of human leukocyte antigen mismatch. Natural killer (NK) cells have a well-defined role in both innate and adaptive immunity and as the first lymphocytes to reconstitute after HSCT and CBT, and they play a significant role in protection against early relapse. In this article, we highlight the uses of CB NK cells in transplantation and adoptive immunotherapy. First, we will describe differences in the phenotype and functional characteristics of NK cells in CB as compared with peripheral blood. Then, we will review some of the obstacles we face in using resting CB NK cells for adoptive immunotherapy, and discuss methods to overcome them. We will review the current literature on killer-cell immunoglobulin-like receptors ligand mismatch and outcomes after CBT. Finally, we will touch on current strategies for the use of CB NK cells in cellular immunotherapy.

Chemokine Receptor Expression on Normal Blood CD56(+) NK-Cells Elucidates Cell Partners That Comigrate during the Innate and Adaptive Immune Responses and Identifies a Transitional NK-Cell Population

Studies of chemokine receptors (CKR) in natural killer- (NK-) cells have already been published, but only a few gave detailed information on its differential expression on blood NK-cell subsets. We report on the expression of the inflammatory and homeostatic CKR on normal blood CD56(+low) CD16(+) and CD56(+high)  CD16(-/+low) NK-cells. Conventional CD56(+low) and CD56(+high) NK-cells present in the normal PB do express CKR for inflammatory cytokines, although with different patterns CD56(+low) NK-cells are mainly CXCR1/CXCR2(+) and CXCR3/CCR5(-/+), whereas mostly CD56(+high) NK-cells are CXCR1/CXCR2(-) and CXCR3/CCR5(+). Both NK-cell subsets have variable CXCR4 expression and are CCR4(-) and CCR6(-). The CKR repertoire of the CD56(+low) NK-cells approaches to that of neutrophils, whereas the CKR repertoire of the CD56(+high) NK-cells mimics that of Th1(+) T cells, suggesting that these cells are prepared to migrate into inflamed tissues at different phases of the immune response. In addition, we describe a subpopulation of NK-cells with intermediate levels of CD56 expression, which we named CD56(+int) NK-cells. These NK-cells are CXCR3/CCR5(+), they have intermediate levels of expression of CD16, CD62L, CD94, and CD122, and they are CD57(-) and CD158a(-). In view of their phenotypic features, we hypothesize that they correspond to a transitional stage, between the well-known CD56(+high) and CD56(+low) NK-cells populations.

Practical NK cell phenotyping and variability in healthy adults

Human natural killer (NK) cells display a wide array of surface and intracellular markers that indicate various states of differentiation and/or levels of effector function. These NK cell subsets exist simultaneously in peripheral blood and may vary among individuals. We examined variety among selected NK cell receptors expressed by NK cells from normal donors, as well as the distribution of select NK cell subsets and NK cell receptor expression over time in several individual donors. Peripheral blood mononuclear cells were evaluated using flow cytometry via fluorochrome-conjugated antibodies against a number of NK cell receptors. Results were analyzed for both mean fluorescence intensity (MFI) and the percent positive cells for each receptor. CD56(bright) and CD56(dim) NK cell subsets were also considered separately, as was variation in receptor expression in NK cell subsets over time in selected individuals. Through this effort, we provide ranges of NK cell surface receptor expression for a local adult population as well as provide insight into intra-individual variation.

KIR3DS1-Specific D0 Domain Polymorphisms Disrupt KIR3DL1 Surface Expression and HLA Binding

KIR3DL1 is a polymorphic inhibitory receptor that modulates NK cell activity through interacting with HLA-A and HLA-B alleles that carry the Bw4 epitope. Amino acid polymorphisms throughout KIR3DL1 impact receptor surface expression and affinity for HLA. KIR3DL1/S1 encodes inhibitory and activating alleles, but despite high homology with KIR3DL1, the activating receptor KIR3DS1 does not bind the same ligand. Allele KIR3DL1*009 resulted from a gene recombination event between the inhibitory receptor allele KIR3DL1*001 and the activating receptor allele KIR3DS1*013. This study analyzed the functional impact of KIR3DS1-specific polymorphisms on KIR3DL1*009 surface expression, binding to HLA, and functional capacity. Flow-cytometric analysis of primary human NK cells as well as transfected HEK293T cells shows that KIR3DL1*009 is expressed at a significantly lower surface density compared with KIR3DL1*001. Using recombinant proteins of KIR3DL1*001, KIR3DL1*009, and KIR3DS1*013 to analyze binding to HLA, we found that although KIR3DL1*009 displayed some evidence of binding to HLA compared with KIR3DS1*013, the binding was minimal compared with KIR3DL1*001 and KIR3DL1*005. Mutagenesis of polymorphic sites revealed that the surface phenotype and reduced binding of KIR3DL1*009 are caused by the combined amino acid polymorphisms at positions 58 and 92 within the D0 extracellular domain. Resulting from these effects, KIR3DL1*009(+) NK cells exhibited significantly less inhibition by HLA-Bw4(+) target cells compared with KIR3DL1*001(+) NK cells. The data from this study contribute novel insight into how KIR3DS1-specific polymorphisms in the extracellular region impact KIR3DL1 surface expression, ligand binding, and inhibitory function.

Flow cytometric immunophenotyping is of great value to diagnosis of natural killer cell neoplasms involving bone marrow and peripheral blood

Natural killer (NK) cell neoplasms are unusual disorders. In this study we compared results of flow cytometric immunophenotype (FCI) with cytomorphology, histopathology and clinical findings in a series of patients with NK cell neoplasms with peripheral blood and/or bone marrow involvement, and the FCI of neoplastic and normal NK cells were compared. Retrospective data and specimens (bone marrow aspiration or peripheral blood) from 71 cases of NK cell neoplasms were obtained. All patients have been demonstrated laboratory and clinical features consistent with NK cell neoplasms, and the subtypes were determined by integrated clinical estimation. Routine 4-color flow cytometry (FCM) using a NK/T cell related antibody panels was performed. NK cell neoplasms were divided into two major subtypes by FCI, namely malignant NK cell lymphoma, including extranodal nasal type NK cell lymphoma (ENKL, 11 cases) and aggressive NK cell lymphoma/leukemia (ANKL, 43 cases), and relative indolent chronic lymphoproliferative disorder of NK cell (CLPD-NK, 17 cases). The former exhibited stronger CD56-expressing, larger forward scatter (FSC) and more usually CD7- and CD16-missing. FCI of CLPD-NK was similar to normal NK cells, but CD56-expressing was abnormal, which was negative in five cases and partially or dimly expressed in eight cases. Cytomorphologic abnormal cells were found on bone marrow slides of 4 cases of ENKL and 30 cases of ANKL. Eight cases of ENKL were positive in bone marrow biopsies, and other three cases were negative. In 32 cases of ANKL which bone marrow biopsies were applied, 21 cases were positive in the first biopsies. Lymphocytosis was found only in six cases of CLPD-NK by cytomorphology, and biopsy pathology was not much useful for diagnosing CLPD-NK. These results suggest that FCM analysis of bone marrow and peripheral blood was superior to cytomorphology, bone marrow biopsy, and immunohistochemistry in sensitivity and early diagnosis for ANKL, stage III/IV ENKL and CLPD-NK. FCI could not only define abnormal NK cells but also determine the malignant classification. It is beneficial for clinical management and further study of NK cell neoplasms.

High IFN-gamma and TNF production by peripheral NK cells of Colombian patients with different clinical presentation of Plasmodium falciparum

BACKGROUND

In Colombia, Plasmodium falciparum infection rarely results in severe disease or mortality compared to infections in African populations. During natural infection NK cells exhibit a cytolytic effect and regulate dendritic cells, macrophages, neutrophils as well as affect antigen specific T and B cell responses. To characterize the NK cells in P. falciparum infected patients of a highly endemic region of Colombia, the degree of NK proliferation and production of IFN gamma and TNF production in these cells were explored.

METHODS

Seventeen patients with acute and three with severe P. falciparum malaria patients from the Northwest region of the country were recruited in the study. In addition, 20 healthy controls were included: 10 from Medellin (no-transmission area) and 10 from the Uraba region (a malaria endemic area). Immunophenotypic analysis of peripheral mononuclear cells was performed by FACS to detect total number of NK cells, subtypes and intracellular IFNγ and TNF production by NK cells in the different patient groups.

RESULTS

The total mean CD56(+)/CD3(-) NK cell proportions in acute and severe malaria subjects were 9.14% (7.15%CD56(dim), 2.01%CD56(bright)) and 19.62% (16.05%CD56(dim), 3.58%CD56(bright)), respectively, in contrast to healthy controls from endemic (total mean CD56(+)/CD3(-)1.2%) and non-endemic area (total mean CD56(+)/CD3(-) 0.67%). Analysis of basal IFNγ and TNF levels confirmed the CD56(bright) NK population as the main cytokine producer (p < 0.0001) in the groups affected with malaria, with the CD56(dim) NK cell exhibiting the highest potential of TNF production after stimulus in the acute malaria group.

CONCLUSIONS

The results confirm the important role of not only CD56(bright) but also of CD56(dim) NK cell populations as producers of the two cytokines in malaria patients in Colombia.

The immunomodulating roles of glycoproteins in epithelial ovarian cancer

The complexity of the immune system demands an intricate defense mechanism by tumors. Ovarian and other tumors employ specific glycoproteins and the associated glycan sequences to modulate immune responses. Glycoproteins enable tumor cells that express or secrete these molecules to evade immune cell attack and induce the immune system to promote tumor growth. This review focuses first on the immune environment in ovarian cancer, and the mechanisms of activation and inhibition that immune cells undergo in order to either attack or ignore a target cell. Next we illustrate the immunomodulatory roles of ovarian cancer-associated glycans and glycoproteins in 1. preventing immune synapse formation, 2. serving as ligands of immune cell receptors, 3. scavenging cytokines and chemokines, and 4. participating in the formation of autoantibodies against the tumor. The importance of these immunomodulating strategies from the view points of understanding the tumor immunology of ovarian tumors, potential origin of such mechanisms, and specific strategies to circumvent the glycoconjugate-mediated suppression of immune responses is discussed in this review.

Effect of the simultaneous administration of glucocorticoids and IL-15 on human NK cell phenotype, proliferation and function

We have previously reported a synergistic effect between hydrocortisone (HC) and IL-15 on promoting natural killer (NK) cell expansion and function. In the present study, we extend our findings to methylprednisolone (MeP) and dexamethasone (Dex), thus ascribing to glucocorticoids (GCs) a general feature as positive regulators of IL-15-mediated effects on NK cells. We demonstrate that each GC when combined with IL-15 in cultures of peripheral blood (PB)-derived CD56(+) cells induces increased expansion of CD56(+)CD3(-) cells displaying high cytolytic activity, IFN-γ production potential and activating receptor expression, including NKp30, NKp44, NKp46, 2B4, NKG2D and DNAM-1. Furthermore, GCs protected NK cells from IL-15-induced cell death. The combination of IL-15 with GCs favored the expansion of a relatively more immature CD16(low/neg) NK cell population, with high expression of NKG2A and CD94, and significantly lower expression of KIR (CD158a and CD158b) and CD57, compared to IL-15 alone. IL-15-expanded NK cells, in the presence or absence of GCs, did not express CD62L, CXCR1 or CCR7. However, the presence of GCs significantly increased the density of CXCR3 and induced strong CXCR4 expression on the surface of NK cells. Our data indicate that IL-15/GC-expanded NK cells, apart from their increased proliferation rate, retain their functional integrity and exhibit a migratory potential rendering them useful for adoptive transfer in NK cell-based cancer immunotherapy.

Antitumor immunity produced by the liver Kupffer cells, NK cells, NKT cells, and CD8 CD122 T cells

Mouse and human livers contain innate immune leukocytes, NK cells, NKT cells, and macrophage-lineage Kupffer cells. Various bacterial components, including Toll-like receptor (TLR) ligands and an NKT cell ligand (α-galactocylceramide), activate liver Kupffer cells, which produce IL-1, IL-6, IL-12, and TNF. IL-12 activates hepatic NK cells and NKT cells to produce IFN-γ, which further activates hepatic T cells, in turn activating phagocytosis and cytokine production by Kupffer cells in a positive feedback loop. These immunological events are essentially evoked to protect the host from bacterial and viral infections; however, these events also contribute to antitumor and antimetastatic immunity in the liver by activated liver NK cells and NKT cells. Bystander CD8⁺CD122⁺ T cells, and tumor-specific memory CD8⁺T cells, are also induced in the liver by α-galactocylceramide. Furthermore, adoptive transfer experiments have revealed that activated liver lymphocytes may migrate to other organs to inhibit tumor growth, such as the lungs and kidneys. The immunological mechanism underlying the development of hepatocellular carcinoma in cirrhotic livers in hepatitis C patients and liver innate immunity as a double-edged sword (hepatocyte injury/regeneration, septic shock, autoimmune disease, etc.) are also discussed.

Analyses of phenotypic and functional characteristics of CX3CR1-expressing natural killer cells

We previously demonstrated a correlation between the frequency of CX3CR1-expressing human natural killer (NK) cells and disease activity in multiple sclerosis and showed that CX3CR1(high) NK cells were more cytotoxic than their CX3CR1(neg/low) counterparts. Here we aimed to determine whether human NK cell fractions defined by CX3CR1 represent distinct subtypes. Phenotypic and functional NK cell analyses revealed that, distinct from CX3CR1(high), CX3CR1(neg/low) NK cells expressed high amounts of type 2 cytokines, proliferated robustly in response to interleukin-2 and promoted a strong up-regulation of the key co-stimulatory molecule CD40 on monocytes. Co-expression analyses of CX3CR1 and CD56 demonstrated the existence of different NK cell fractions based on the surface expression of these two surface markers, the CX3CR1(neg) CD56(bright), CX3CR1(neg) CD56(dim) and CX3CR1(high) CD56(dim) fractions. Additional investigations on the expression of NK cell receptors (KIR, NKG2A, NKp30 and NKp46) and the maturation markers CD27, CD62L and CD57 indicated that CX3CR1 expression of CD56(dim) discriminated between an intermediary CX3CR1(neg)  CD56(dim) and fully mature CX3CR1(high) CD56(dim) NK cell fractions. Hence, CX3CR1 emerges as an additional differentiation marker that may link NK cell maturation with the ability to migrate to different organs including the central nervous system.

Analyses of phenotypic and functional characteristics of CX3CR1-expressing natural killer cells

We previously demonstrated a correlation between the frequency of CX3CR1-expressing human natural killer (NK) cells and disease activity in multiple sclerosis and showed that CX3CR1(high) NK cells were more cytotoxic than their CX3CR1(neg/low) counterparts. Here we aimed to determine whether human NK cell fractions defined by CX3CR1 represent distinct subtypes. Phenotypic and functional NK cell analyses revealed that, distinct from CX3CR1(high), CX3CR1(neg/low) NK cells expressed high amounts of type 2 cytokines, proliferated robustly in response to interleukin-2 and promoted a strong up-regulation of the key co-stimulatory molecule CD40 on monocytes. Co-expression analyses of CX3CR1 and CD56 demonstrated the existence of different NK cell fractions based on the surface expression of these two surface markers, the CX3CR1(neg) CD56(bright), CX3CR1(neg) CD56(dim) and CX3CR1(high) CD56(dim) fractions. Additional investigations on the expression of NK cell receptors (KIR, NKG2A, NKp30 and NKp46) and the maturation markers CD27, CD62L and CD57 indicated that CX3CR1 expression of CD56(dim) discriminated between an intermediary CX3CR1(neg)  CD56(dim) and fully mature CX3CR1(high) CD56(dim) NK cell fractions. Hence, CX3CR1 emerges as an additional differentiation marker that may link NK cell maturation with the ability to migrate to different organs including the central nervous system.

Natural killer cell neoplasm: biology and pathology

Natural killer (NK) cell neoplasm is a heterogeneous disease group. In the latest World Health Organization (WHO) classification of tumours of hematopoietic and lymphoid tissues (2008), disease entities considered as NK-cell derivation include NK-lymphoblastic leukemia/lymphoma, chronic lymphoproliferative disorders of NK cells, aggressive NK-cell leukemia, and extranodal NK-cell lymphoma, nasal-type. Despite recent advances in NK-cell research, which have expanded our understanding of the biology of NK-cell neoplasm, it cannot yet be sharply delineated from myeloid neoplasms and T-cell neoplasms even in some "well-known" entity, such as extranodal NK/T-cell lymphoma. This review describes current knowledge of the biology of NK cells and pathology of NK neoplasms as classified in the 2008 WHO classification of tumours of hematopoietic and lymphoid tissues.

CD57 defines a functionally distinct population of mature NK cells in the human CD56dimCD16+ NK-cell subset

Natural killer (NK) cells are innate immune lymphocytes that express a heterogeneous repertoire of germline-encoded receptors and undergo a distinct pattern of maturation. CD57 is a marker of terminal differentiation on human CD8(+) T cells. Very few newborn or fetal NK cells express CD57; however, the frequency of CD57-bearing NK cells increases with age. We assessed the transcriptional, phenotypic, and functional differences between CD57(+) and CD57(-) NK cells within the CD56(dim) mature NK subset. CD57(+) NK cells express a repertoire of NK-cell receptors, suggestive of a more mature phenotype, and proliferate less when stimulated with target cells and/or cytokines. By contrast, a higher frequency of CD57(+) NK cells produced interferon-γ and demonstrated more potent lytic activity when these cells were stimulated through the activating receptor CD16; however, they are less responsive to stimulation by interleukin-12 and interleukin-18. Finally, CD57 expression is induced on CD57(-)CD56(dim) NK cells after activation by interleukin-2. A combination of a mature phenotype, a higher cytotoxic capacity, a higher sensitivity to stimulation via CD16, with a decreased responsiveness to cytokines, and a decreased capacity to proliferate suggest that CD57(+) NK cells are highly mature and might be terminally differentiated.

MTS dye based colorimetric CTLL-2 cell proliferation assay for product release and stability monitoring of interleukin-15: assay qualification, standardization and statistical analysis

A colorimetric cell proliferation assay using soluble tetrazolium salt [(CellTiter 96(R) Aqueous One Solution) cell proliferation reagent, containing the (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt) and an electron coupling reagent phenazine ethosulfate], was optimized and qualified for quantitative determination of IL-15 dependent CTLL-2 cell proliferation activity. An in-house recombinant Human (rHu)IL-15 reference lot was standardized (IU/mg) against an international reference standard. Specificity of the assay for IL-15 was documented by illustrating the ability of neutralizing anti-IL-15 antibodies to block the product specific CTLL-2 cell proliferation and the lack of blocking effect with anti-IL-2 antibodies. Under the defined assay conditions, the linear dose-response concentration range was between 0.04 and 0.17ng/ml of the rHuIL-15 produced in-house and 0.5-3.0IU/ml for the international standard. Statistical analysis of the data was performed with the use of scripts written in the R Statistical Language and Environment utilizing a four-parameter logistic regression fit analysis procedure. The overall variation in the ED(50) values for the in-house reference standard from 55 independent estimates performed over the period of 1year was 12.3% of the average. Excellent intra-plate and within-day/inter-plate consistency was observed for all four parameter estimates in the model. Different preparations of rHuIL-15 showed excellent intra-plate consistency in the parameter estimates corresponding to the lower and upper asymptotes as well as to the 'slope' factor at the mid-point. The ED(50) values showed statistically significant differences for different lots and for control versus stressed samples. Three R-scripts improve data analysis capabilities allowing one to describe assay variations, to draw inferences between data sets from formal statistical tests, and to set up improved assay acceptance criteria based on comparability and consistency in the four parameters of the model. The assay is precise, accurate and robust and can be fully validated. Applications of the assay were established including process development support, release of the rHuIL-15 product for pre-clinical and clinical studies, and for monitoring storage stability.

Relative quantification of canine CD56 mRNA expression by real-time polymerase chain reaction method in normal tissues and activated lymphocytes

Real-time PCR was optimized for the quantification of canine CD56 mRNA expression. This study was conducted to easily quantify canine CD56 expression and to identify its expression in normal tissues, peripheral blood mononuclear cells and activated lymphocytes in dogs. This assay revealed the highest level of CD56 mRNA expression in the normal canine brain, followed by the lung, kidney and liver. CD56 mRNA expression level in peripheral blood mononuclear cells was considerably lower; among activated lymphocytes in vitro, CD56 mRNA expression was increased.

[Gene therapy of SCID-X1]

X-linked severe combined immunodeficiency (SCID-X1) is an inherited disease caused by inactivating mutations in the gene encoding the interleukin 2 receptor common gamma chain (IL2RG), which is located on the X-chromosome. Affected boys fail to develop two major effector cell types of the immune system (T cells and NK cells) and suffer from a functional B cell defect. Although drugs such as antibiotics can offer partial protection, the boys normally die in the first year of life in the absence of a curative therapy. For a third of the children, bone marrow transplantation from a fully matched donor is available and can cure the disease without major side effects. Mismatched bone marrow transplantation, however, is complicated by severe and potentially lethal side effects. Over the past decade, scientists worldwide have developed new treatments by introducing a correct copy of the IL2RG-cDNA. Gene therapy was highly effective when applied in young children. However, in a few patients the IL2RG-gene vector has unfortunately caused leukaemia. Activation of cellular proto-oncogenes by accidental integration of the gene vector has been identified as the underlying mechanism. In future clinical trials, improved vector technology in combination with other protocol modifications may reduce the risk of this side effect.

Phenotypically and functionally distinct subsets of natural killer cells in human PBMCs

Human natural killer (NK) cells are one major component of lymphocytes that mediate early protection against viruses and tumor cells, and play an important role in immune regulatory functions. In this study, we demonstrated that human NK cells could be divided into four subsets, CD56hi CD16(-), CD56lo CD16(-), CD56+CD16+ and CD56(-)CD16+, based on the expression of cell surface CD56 and CD16 molecules. Phenotypic analysis of NK cell subsets indicated that the expression of activation markers, adhesion molecules, memory cell markers, inhibitory and activating receptors, and intracellular proteins (granzyme B and perforin) were heterogeneous. Following interleukin (IL)-2 stimulation, interferon-gamma was preferentially produced by CD56+CD16(-) NK cells and this subset showed more proliferative capacity. The cytolytic activity of both CD56+CD16(-) and CD56+/-CD16+ subsets could be augmented in response to IL-2. The data provided a new definition for NK cell subsets demonstrating their phenotypic and functional diversity and possible stage of NK cell differentiation in peripheral blood.

CD56bright human NK cells differentiate into CD56dim cells: role of contact with peripheral fibroblasts

Human NK cells are divided into CD56(bright)CD16(-) cells and CD56(dim)CD16(+) cells. We tested the hypothesis that CD56(bright) NK cells can differentiate into CD56(dim) cells by prospectively isolating and culturing each NK subset in vitro and in vivo. Our results show that CD56(bright) cells can differentiate into CD56(dim) both in vitro, in the presence of synovial fibroblasts, and in vivo, upon transfer into NOD-SCID mice. In vitro, this differentiation was inhibited by fibroblast growth factor receptor-1 Ab, demonstrating a role of the CD56 and fibroblast growth factor receptor-1 interaction in this process. Differentiated CD56(dim) cells had reduced IFN-gamma production but increased perforin expression and cytolysis of cell line K562 targets. Flow cytometric fluorescent in situ hybridization demonstrated that CD56(bright) NK cells had longer telomere length compared with CD56(dim) NK cells, implying the former are less mature. Our data support a linear differentiation model of human NK development in which immature CD56(bright) NK cells can differentiate into CD56(dim) cells.

Helper roles of NK and CD8+ T cells in the induction of tumor immunity. Polarized dendritic cells as cancer vaccines

The work in our laboratory addresses two interrelated areas of dendritic cell (DC) biology: (1) the role of DCs as mediators of feedback interactions between NK cells, CD8+ and CD4+ T cells; and (2) the possibility to use such feedback and the paradigms derived from anti-viral responses, to promote the induction of therapeutic immunity against cancer. We observed that CD8+ T cells and NK cells, the classical "effector" cells, also play "helper" roles, regulating ability of DCs to induce type-1 immune immunity, critical for fighting tumors and intracellular pathogens. Our work aims to delineate which pathways of NK and CD8+ T cell activation result in their helper activity, and to identify the molecular mechanisms allowing them to induce type-1 polarized DCs (DC1s) with selectively enhanced ability to promote type-1 responses and anti-cancer immunity. The results of these studies allowed us and our colleagues to design phase I/II clinical trials incorporating the paradigms of DC polarization and helper activity of effector cells in cancer immunotherapy.

HIV-1 Nef impairs the dynamic of DC/NK crosstalk: different outcome of CD56(dim) and CD56(bright) NK cell subsets

Dendritic cells (DCs) and natural killer (NK) cells are essential components of the innate immunity and play a critical role in the first phase of host defense against infection. Interactions between DCs and NK cells have been demonstrated in a variety of settings, with evidence emerging of complex bidirectional crosstalk between the two cell types. The accessory HIV-1 Nef protein is a crucial determinant for viral replication and pathogenesis. We previously demonstrated that Nef, hijacking DC functional activity, subverts the DC arm of immune response to escape the adaptive immune attack. Here, we monitor the effect of Nef on the outcome of the innate immune response, focusing on the impact of Nef on DC/NK crosstalk. We demonstrate that Nef up-regulates the ability of DCs to stimulate the immunoregulatory NK cells (CD56(bright)) as assessed by the activated phenotype, up-regulation of their proliferative response and INF-gamma release. On the other hand, Nef-pulsed DCs inhibit cytotoxic NK cells (CD56(dim)), as assessed by the reduced HLA-DR surface expression, reduced proliferation and cytotoxic activity. Moreover, in the presence of Nef-pulsed DCs, we found a significant up-regulation of TNF-alpha secretion and a significant reduction of IL-10, GM-CSF, MIP-1alpha and RANTES secretion. Our findings suggest that the Nef-induced dysregulation in the DC/NK cell crosstalk may represent a potential mechanism through which HIV escapes innate immune surveillance.

Induction of CD16+ CD56bright NK cells with antitumour cytotoxicity not only from CD16- CD56bright NK Cells but also from CD16- CD56dim NK cells

The aim of this study was to examine the effect of cytokines on different subsets of NK cells, while especially focusing on CD16(-) CD56(dim) cells and CD16(-) CD56(bright) cells. When human peripheral blood mononuclear cells (PBMC) were cultured with a combination of IL-2, IL-12 and IL-15 for several days, a minor population of CD56(bright) NK cells expanded up to 15%, and also showed potent cytotoxicities against various cancer cells. Sorting experiments revealed that unconventional CD16(-) CD56(+) NK cells (CD16(-) CD56(dim) NK cells and CD16(-) CD56(bright) NK cells, both of which are less than 1% in PBMC) much more vigorously proliferated after cytokine stimulation, whereas predominant CD16(+) CD56(dim) NK cells proliferated poorly. In addition, many of the resting CD16(-) CD56(bright) NK cells developed into CD16(+) CD56(bright) NK cells, and CD16(-) CD56(dim) NK cells developed into CD16(-) CD56(bright) NK cells and also further into CD16(+) CD56(bright) NK cells by the cytokines. CSFE label experiments further substantiated the proliferation capacity of each subset and the developmental process of CD16(+) CD56(bright) NK cells. Both CD16(-) CD56(dim) NK cells and CD16(-) CD56(bright) NK cells produced large amounts of IFN-gamma and Fas-ligands. The CD16(+) CD56(bright) NK cells showed strong cytotoxicities against not only MHC class I (-) but also MHC class I (+) tumours regardless of their expression of CD94/NKG2A presumably because they expressed NKG2D as well as natural cytotoxicity receptors. The proliferation of CD16(+) CD56(bright) NK cells was also induced when PBMC were stimulated with penicillin-treated Streptococcus pyogenes, thus suggesting their role in tumour immunity and bacterial infections.

Good manufacturing practices production of natural killer cells for immunotherapy: a six-year single-institution experience

BACKGROUND

Natural killer (NK) cells, a subset of lymphocytes and part of the innate immune system, play a crucial role in defense against cancer and viral infection. Herein is a report on the experience of clinical-scale, good manufacturing practices (GMPs) production of NK cells to treat advanced cancer.

STUDY DESIGN AND METHODS

Two types of NK cell enrichments were performed on nonmobilized peripheral blood mononuclear cell apheresis collections with a cell selection system (CliniMACS, Miltenyi): CD3 cell depletion to enrich for NK cells and CD3 cell depletion followed by CD56 cell selection to obtain a more pure NK cell product. After overnight incubation with interleukin-2 (IL-2), cells were washed, resuspended in 5 percent human serum albumin, and then released for infusion.

RESULTS

A total of 70 NK cell therapy products have been manufactured for patient infusion since 2000. For the CD3 cell-depleted NK cell products, the mean purity, recovery, and viability were 38, 79, and 86 percent, respectively. For the CD3 cell-depleted/CD56 cell-enriched NK cell products, the mean purity, recovery, and viability were 90, 19, and 85 percent, respectively. Gram stain, sterility, and endotoxin testing were all within acceptable limits for established lot release. Compared to the resting processed cells, IL-2 activation significantly increased the function of cells in cytotoxicity assays.

CONCLUSION

Clinical-scale production of NK cells is efficient and can be performed under GMPs. The purified NK cell product results in high NK cell purity with minimal contamination by T cells, monocytes, and B cells, but it requires more time for processing and results in a lower NK cell recovery when compared to NK cell enrichment with CD3 cell depletion alone. Additional laboratory studies and results from clinical trials will identify the best source and type of NK cell product.