Different combinations of cytokines and activating receptor stimuli are required for human natural killer cell functional diversity

Identification of the predominant human NK cell effector subset mediating ADCC against HIV-infected targets coated with BNAbs or plasma from PLWH

The potential of immunotherapy strategies utilizing broadly neutralizing antibodies (BNAbs), such as 3BNC117 and 10-1074, to limit viral replication while also facilitating clearance of HIV infected cells has heightened interest in identifying the predominant NK effector subset(s) capable of mediating antibody dependent cellular cytotoxicity (ADCC). Utilizing advanced polychromatic flow cytometry, we identified that CD57 positive NK cells from ART-suppressed in People Living With HIV (PLWH) expressed significantly higher levels of the CD16 FcγR receptor, 2B4 ADCC coreceptor, and HLA-DR activation marker while NKG2C positive NK cells expressed significantly higher levels of the CD2 ADCC coreceptor (p < 0.001, n = 32). Functionally, CD57 positive NK cells from ART-suppressed PLWH with either high or low NKG2C expansion exhibited significantly enhanced degranulation and IFN-γ production against heterologous gp120-coated ADCC targets coated with HIV reference plasma compared to CD57 negative NK cells (p = 0.0029, n = 11). CD57 positive NK cells from control donors lacking NKG2C expansion also exhibited significantly more degranulation and IFN-γ production at every timepoint tested against both heterologous ADCC targets (p = 0.019, n = 9) and HIV-1 infected autologous CD4⁺ primary T cells coated with BNAbs. Together, our data support CD57 positive and NKG2C positive NK cells as the predominant ADCC effector subsets capable of targeting HIV-infected CD4⁺ cells in the presence of 3BNC117 and 10-1074 immunotherapy.

Immunological Drivers in Graves' Disease: NK Cells as a Master Switcher

Graves' disease (GD) is a common autoimmune cause of hyperthyroidism, which is eventually related to the generation of IgG antibodies stimulating the thyrotropin receptor. Clinical manifestations of the disease reflect hyperstimulation of the gland, causing thyrocyte hyperplasia (goiter) and excessive thyroid hormone synthesis (hyperthyroidism). The above clinical manifestations are preceded by still partially unraveled pathogenic actions governed by the induction of aberrant phenotype/functions of immune cells. In this review article we investigated the potential contribution of natural killer (NK) cells, based on literature analysis, to discuss the bidirectional interplay with thyroid hormones (TH) in GD progression. We analyzed cellular and molecular NK-cell associated mechanisms potentially impacting on GD, in a view of identification of the main NK-cell subset with highest immunoregulatory role.

Characterization and functional analysis of novel circulating NK cell sub-populations

Natural killer (NK) cells are innate lymphoid cells having potent cytolytic function that provide host defense against microbial infections and tumors. Using our generated monoclonal antibody (mAb), named FE-1H10, new NK cell sub-populations in peripheral blood were identified. The molecules recognized by mAb FE-1H10 were expressed on a sub-population of CD3-CD56dim NK cells. The epitope recognized by mAb FE-1H10 was demonstrated to be N-glycan and proven to be different from CD57. Upon K562 stimulation, the CD56dimFE-1H10+ NK cell sub-population exhibited significantly lower cytolytic function with low ability to degranulate and release cytolytic granules compared to the CD56dimFE-1H10- NK cell sub-population. Moreover, the CD56dimFE-1H10+ NK cells produced less IFN-γ and TNF-α than the CD56dimFE-1H10- NK cells. We demonstrated here that mAb FE-1H10 could identify two sub-populations of circulating CD56dim NK cells with different functions. Our discovery of new sub-populations of NK cells improves our understanding of NK cell biology and may lead to the development of new approaches for NK cell therapy.

From synthetic biology to human therapy: engineered mammalian cells

Mammalian synthetic biology has evolved to become a key driver of biomedical innovation in the area of cell therapy. Advances in receptor engineering, immunotherapy and cell implants promise new treatment options for complex diseases. Synthetic receptors have already found applications in cellular immunotherapy for cancer treatment, and are being introduced into the field of cell implants. Here, we discuss prospects for the next generation of engineered mammalian cells for human therapy, highlighting selected recent studies.

Ovalbumin induces natural killer cells to secrete Th2 cytokines IL‑5 and IL‑13 in a mouse model of asthma

Asthma is a chronic lung disease characterized by an imbalance of T-helper (Th)1/Th2 cells and their cytokine profiles. Natural killer (NK) cells constitute a considerable subset of the lymphocyte population in the lungs, and provide protection against respiratory infection by fungi, bacteria and viruses. However, the mechanism by which NK cells are involved in asthma remains to be fully elucidated. The present study analyzed the dynamic changes of NK cells and their subsets during the development of the ovalbumin (OVA)-induced allergic airway response. Lung tissues were histologically examined for cell infiltration and mucus hypersecretion. The number, activity and cytokine-secreting ability of NK cells was determined by flow cytometry. The results showed that the percentage of NK cells in the lung was decreased following OVA sensitization and challenge. However, NK cells exhibited enhanced activity and secreted more Th2 cytokines (IL-5 and IL-13) following OVA challenge. Furthermore, the proportion of CD11b⁻ NK subsets increased with the development of asthma, and CD11b⁻ CD27⁻ NK cells were the primary NK subset producing Th2 cytokines. These findings suggest that, although NK cells are not the crucial type of lymphocytes involved in asthma, OVA induces NK cells to secrete Th2 cytokines that may be involved in the pathogenesis of asthma.

Altered natural killer cell cytokine profile in type 2 autoimmune hepatitis

Type 2 autoimmune hepatitis (AIH-2) is a rare disease presenting in early childhood. The immunopathogenetic mechanisms are poorly characterized, although a defect of regulatory T cells (Treg) has been shown. There is virtually no information on innate immune responses and natural killer (NK) cells in particular. We have performed an extended immunophenotypic and functional analysis of NK cells in children with AIH-2. We show that NK cell frequency is reduced in this setting and that the balance between NK activating and inhibitory receptors is skewed toward activation. More importantly, NK cells display an altered cytokine pattern characterized by increased IFNγ and reduced IL2 production which could contribute to impaired Treg function. Exposure of mononuclear cells to IL2 resulted in normalization of NK IFNγ production. Thus, our findings support treatment of AIH-2 with low-dose IL2, which would result in normalization of NK cell function and expansion of the Treg cell subset.

Mass Cytometry Analytical Approaches Reveal Cytokine-Induced Changes in Natural Killer Cells

BACKGROUND

Natural killer (NK) cells have antiviral and antitumor activity that could be harnessed for the treatment of infections and malignancies. To maintain cell viability and enhance antiviral and antitumor effects, NK cells are frequently treated with cytokines. Here they performed an extensive assessment of the effects of cytokines on the phenotype and function of human NK cells.

METHODS

They used cytometry by time-of-flight (CyTOF) to evaluate NK cell repertoire changes after stimulation with interleukin (IL)-2, IL-15 or a combination of IL-12/IL-15/IL-18. To analyze the high dimensional CyTOF data, they used several statistical and visualization tools, including viSNE (Visualization of t-Distributed Stochastic Neighbor Embedding), Citrus (Cluster identification, characterization, and regression), correspondence analysis, and the Friedman-Rafsky test.

RESULTS

All three treatments (IL-2, IL-15, and IL-12/IL-15/IL-18) increase expression of CD56 and CD69. The effects of treatment with IL-2 and IL-15 are nearly indistinguishable and characterized principally by increased expression of surface markers including CD56, NKp30, NKp44, and increased expression of functional markers, such as perforin, granzyme B, and MIP-1β. The combination of IL-12/IL-15/IL-18 induces a profound shift in the repertoire structure, decreasing expression of CD16, CD57, CD8, NKp30, NKp46, and NKG2D, and dramatically increasing expression of IFN-γ.

CONCLUSIONS

CyTOF provides insights into the effects of cytokines on the phenotype and function of NK cells, which could inform future research efforts and approaches to NK cell immunotherapy. There are several analytical approaches to CyTOF data, and the appropriate method should be carefully selected based on which aspect of the dataset is being explored. © 2016 International Clinical Cytometry Society.

IFN-α augments natural killer-mediated antibody-dependent cellular cytotoxicity of HIV-1-infected autologous CD4+ T cells regardless of major histocompatibility complex class 1 downregulation

DESIGN

We have previously shown that IFN-α stimulation augments direct natural killer (NK) cell lysis of autologous CD4 primary T cells infected with certain HIV-1 isolates based upon major histocompatibility complex class 1 (MHC-1) downregulation capacity. Here, we investigated if antibody-dependent cellular cytotoxicity (ADCC) could trigger lysis of HIV-1 isolates that were resistant to direct NK lysis and if IFN-α prestimulation of NK cells could further enhance ADCC.

METHODS

Using broadly neutralizing monoclonal antibodies against gp120 (VRC01 or PGV04) or plasma from HIV-1-infected patients (ART-suppressed or elite controller) to trigger ADCC, we measured NK cell chromium release cytotoxicity against HIV-1-infected autologous CD4 primary T cells and NK cell CD107a degranulation against gp120-coated CD4 T cells. Total or NK-depleted peripheral blood mononuclear cells were used as effectors in the presence or absence of IFN-α prestimulation.

RESULTS

Plasma from HIV-1-infected patients and monoclonal antibodies against gp120 could trigger NK-dependent ADCC lysis of viral isolates that were resistant to direct NK cell lysis following IFN-α stimulation. In contrast, viral isolates that exhibited potent MHC-I downregulation capacity could be lysed by NK cells through either IFN-α stimulated direct cytotoxicity or through ADCC. When utilized in combination, IFN-α prestimulation significantly augmented ADCC lysis of HIV-1-infected target cells and increased NK cell CD107a degranulation against gp120-coated ADCC targets (P < 0.05, n = 6).

CONCLUSION

HIV-1 isolates with lower MHC-I downregulation capacity are resistant to direct lysis following IFN-α stimulation but retain sensitivity to ADCC. IFN-α prestimulation can significantly increase NK-mediated clearance of HIV-1-infected target cells by both ADCC and/or direct cytotoxicity depending on MHC downregulation status.

Lysis of HIV-1-infected autologous CD4+ primary T cells by interferon-alpha-activated NK cells requires NKp46 and NKG2D

OBJECTIVE

Autologous HIV-1-infected CD4 primary T cells (aHIVCD4) have been shown to be largely resistant to natural killer (NK)-cell-mediated lysis because of viral strategies of immune evasion. We have previously shown that a preactivation of NK cells with plasmacytoid dendritic cells can significantly augment lysis of aHIVCD4 through a mechanism dependent on interferon-alpha (IFN-α).

DESIGN

The goal of the present study is to identify the specific NK-activating receptors involved in NK lysis of aHIVCD4 following IFN-α activation.

METHODS

Peripheral blood mononuclear cells (PBMC) were incubated with aHIVCD4 to induce the secretion of endogenous levels of IFN-α and drive NK activation. We then utilized a standard chromium lysis assay to assess the degree of IFN-α-activated lysis of aHIVCD4 in the presence or absence of masking antibodies to a panel of NK-activating receptors and co-receptors.

RESULTS

Direct recognition of HIV-1-infected, but not uninfected, autologous CD4 primary T cells by PBMC induced the secretion IFN-α (median 2280 pg/ml, P < 0.001, n = 9) that, in turn, activated NK cells (P < 0.001, n = 12) and significantly increased their cytolytic potential against aHIVCD4 (P < 0.01, n = 12). The masking of NKp46 (P < 0.01, n = 8) and NKG2D (P < 0.05, n = 8), but not 2B4, NTBA, NKp30 or NKp44, significantly reduced IFN-α-activated lysis of aHIVCD4.

CONCLUSIONS

Taken together, these results demonstrate that endogenous levels of IFN-α secreted by plasmacytoid dendritic cells induce NK cells to lyse aHIVCD4 via the engagement of NKp46 and NKG2D.

Priming of Human Resting NK Cells by Autologous M1 Macrophages via the Engagement of IL-1β, IFN-β, and IL-15 Pathways

The cross talk between NK cells and macrophages is emerging as a major line of defense against microbial infections and tumors. This study reveals a complex network of soluble mediators and cell-to-cell interactions allowing human classically activated (M1) macrophages, but not resting (M0) or alternatively activated (M2) macrophages, to prime resting autologous NK cells. In this article, we show that M1 increase NK cell cytotoxicity by IL-23 and IFN-β-dependent upregulation of NKG2D, IL-1β-dependent upregulation of NKp44, and trans-presentation of IL-15. Moreover, both IFN-β-dependent cis-presentation of IL-15 on NK cells and engagement of the 2B4-CD48 pathway are used by M1 to trigger NK cell production of IFN-γ. The disclosure of these synergic cellular mechanisms regulating the M1-NK cell cross talk provides novel insights to better understand the role of innate immune responses in the physiopathology of tumor biology and microbial infections.

Dopamine inhibits the effector functions of activated NK cells via the upregulation of the D5 receptor

Several lines of evidence indicate that dopamine (DA) plays a key role in the cross-talk between the nervous and immune systems. In this study, we disclose a novel immune-regulatory role for DA: inhibition of effector functions of activated NK lymphocytes via the selective upregulation of the D5 dopaminergic receptor in response to prolonged cell stimulation with rIL-2. Indeed, engagement of this D1-like inhibitory receptor following binding with DA suppresses NK cell proliferation and synthesis of IFN-γ. The inhibition of IFN-γ production occurs through blocking the repressor activity of the p50/c-REL dimer of the NF-κB complex. Indeed, the stimulation of the D5 receptor on rIL-2-activated NK cells inhibits the binding of p50 to the microRNA 29a promoter, thus inducing a de novo synthesis of this miRNA. In turn, the increased levels of microRNA 29a were inversely correlated with the ability of NK cells to produce IFN-γ. Taken together, our findings demonstrated that DA switches off activated NK cells, thus representing a checkpoint exerted by the nervous system to control the reactivity of these innate immune effectors in response to activation stimuli and to avoid the establishment of chronic and pathologic inflammatory processes.

NK Cell Subset Redistribution during the Course of Viral Infections

Natural killer (NK) cells are important effectors of innate immunity that play a critical role in the control of human viral infections. Indeed, given their capability to directly recognize virally infected cells without the need of specific antigen presentation, NK cells are on the first line of defense against these invading pathogens. By establishing cellular networks with a variety of cell types such as dendritic cells, NK cells can also amplify anti-viral adaptive immune responses. In turn, viruses evolved and developed several mechanisms to evade NK cell-mediated immune activity. It has been reported that certain viral diseases, including human immunodeficiency virus-1 as well as human cytomegalovirus infections, are associated with a pathologic redistribution of NK cell subsets in the peripheral blood. In particular, it has been observed the expansion of unconventional CD56(neg) NK cells, whose effector functions are significantly impaired as compared to that of conventional CD56(pos) NK cells. In this review, we address the impact of these two chronic viral infections on the functional and phenotypic perturbations of human NK cell compartment.