Natural Killer Cell Antibody-dependent Cellular Cytotoxicity Research Articles

Spatial localization of CD16a at the human NK cell ADCC lytic synapse.

Natural Killer (NK) cells utilize effector functions, including antibody-dependent cellular cytotoxicity (ADCC), for the clearance of viral infection and cellular malignancies. NK cell ADCC is mediated by Fc γ RIIIa (CD16a) binding to the fragment crystallizable (Fc) region of immunoglobulin G (IgG) within immune complexes on a target cell surface. While antibody-induced clustering of CD16a is thought to drive ADCC, the molecular basis for this activity has not been fully described. Here we use MINFLUX nanoscopy to map the spatial distribution of stoichiometrically labeled CD16a across the NK cell membrane, revealing the presence of pairs of CD16a molecules with intra-doublet distance of approximately 17 nm. NK cells activated on supported lipid bilayers by Trastuzumab results in an increase of synaptic regions with greater CD16a density. Our results provide the highest spatial resolution yet described for CD16a imaging, offering new insight into how CD16a organization within the immune synapse could influence ADCC activity. MINFLUX holds great promise to further unravel the molecular details driving CD16a-based activation of NK cells.

Knockdowns of CD3zeta Chain in Primary NK Cells Illustrate Modulation of Antibody-Dependent Cellular Cytotoxicity Against Human Immunodeficiency Virus-1.

Multifaceted natural killer (NK) cell activities are indispensable for controlling human immunodeficiency virus (HIV)-1 transmission and pathogenesis. Among the diverse functions of NK cells, antibody-dependent cellular cytotoxicity (ADCC) has been shown to predict better HIV-1 protection. ADCC is initiated by the engagement of an Fc γ receptor CD16 with an Fc portion of the antibody, leading to phosphorylation of the CD3 ζ chain (CD3ζ) and Fc receptor γ chain (FcRγ) as well as downstream signaling activation. Though CD3ζ and FcRγ were thought to have overlapping roles in NK cell ADCC, several groups have reported that CD3ζ-mediated signals trigger a more robust ADCC. However, few studies have illustrated the direct contribution of CD3ζ in HIV-1-specific ADCC. To further understand the roles played by CD3ζ in HIV-1-specific ADCC, we developed a CD3ζ knockdown system in primary human NK cells. We observed that HIV-1-specific ADCC was inhibited by CD3ζ perturbation. In summary, we demonstrated that CD3ζ is important for eliciting HIV-1-specific ADCC, and this dynamic can be utilized for NK cell immunotherapeutics against HIV-1 infection and other diseases.

NK Cytotoxicity Mediated by NK-92 Cell Lines Expressing Combinations of Two Allelic Variants for FCGR3.

Natural killer (NK) cells play an important role in the surveillance of viral infections and cancer. NK cell antibody-dependent cellular cytotoxicity (ADCC) and direct cytotoxicity are mediated by the recognition of antibody-coated target cells through the Fc gamma receptor IIIA (FcγRIIIa/CD16) and by ligands of activating/inhibitory NK receptors, respectively. Allelic variants of the FCGR3A gene include the high-affinity single-nucleotide polymorphism (SNP) rs396991 (V176F), which is associated with the efficacy of monoclonal antibody (mAb) therapies, and the SNP rs10127939 (L66H/R). The contribution of FCGR3A SNPs to NK cell effector functions remains controversial; therefore, we generated a panel of eight NK-92 cell lines expressing specific combinations of these SNPs and tested their cytotoxicities. NK-92 cells were stably transfected with plasmids containing different combinations of FCGR3A SNPs. Messenger RNA and FcγRIIIa/CD16 cell surface expressions were detected using new generation sequencing (NGS) and flow cytometry, respectively. All FcγRIIIa/CD16-transfected NK-92 cell lines exhibited robust ADCC against three different target cell lines with minor differences. In addition, enhanced direct NK cytotoxicity against K562 target cells was observed, suggesting a mechanistic role of FcγRIIIa/CD16 in direct NK cytotoxicity. In conclusion, we generated eight FcγRIIIa/CD16-transfected NK-92 cell lines carrying different combinations of two of the most studied FCGR3A SNPs, representing the major genotypes described in the European population. The functional characterization of these cell lines revealed differences in ADCC and direct NK cytotoxicity that may have implications for the design of adoptive cancer immunotherapies using NK cells and tumor antigen-directed mAbs.

Abstract 83: NK cell ADCC assays: Leveraging flow cytometry and reporter cell lines for enhanced biological relevance and throughput

Abstract Amid the growing arsenal of cancer treatments, antibody-dependent cellular cytotoxicity (ADCC) assays have emerged as a significant contributor to the quest for more effective therapies. The ADCC-based antibody therapy often exploits Natural Killer (NK) cells as effectors. This immunotherapeutic approach harnesses the innate cytotoxic potential of NK cells, offering a promising solution for the precision targeting of malignant cells. In this study, we employed two methods that can be used to measure ADCC potency and specificity during preclinical drug discovery. The first was a flow cytometry-based approach that focused on enhancing biological relevance by utilizing primary human peripheral blood mononuclear cells (PBMCs) as a source for NK effector cells. To this end, target cells were fluorescently labeled with CFSE and cultured with freshly isolated PBMCs at 3 effector to target (E:T) ratios, in the presence of ADCC antibody. After 16h incubation, a viability dye was added, and percent cytotoxicity was measured in CFSE+ targets cells by flow cytometry. The second method offered a high-throughput plate reader-based approach (ADCC Reporter Bioassay; Promega), that utilized an ADCC reporter effector cell line harboring a luciferase cassette driven by an NFAT promoter, which is activated when effector and targets cells are bridged by a therapeutic antibody. Cytotoxicity was read out by measuring light output on a Cytation 3 plate imaging reader (Agilent Technologies) after a 6h cell culture incubation using the recommended 6:1 E:T ratio. Preclinical application for both assays was demonstrated using an anti-HER2 therapeutic antibody (trastuzumab) against BT-474, which is a HER2 positive cell line. To demonstrate specificity, an anti-VEGF antibody (bevacizumab) and Hs 578T cells (HER2 low) were used as controls. Our results revealed trastuzumab induced a strong dose-dependent increase in cytotoxicity in the BT-474 cells but not the Hs 578T cell line (range: 40-70%) while bevacizumab failed to induce any cytotoxicity above background levels at any concentration. Furthermore, the flow cytometry and plate reader methodologies produced similar trends. In summary, both applications can be used to produce reliable ADCC drug screening assessments. Additional considerations include investigational needs surrounding high throughput capability versus biological relevance. Unlike traditional models using immortalized cell lines, primary human PBMCs more faithfully recapitulate the physiological interactions between effector cells and target cells. On the other hand, the more streamlined reporter cell line approach not only accelerates assay throughput but also ensures consistent and reliable results in an attractive option for large-scale screening and drug development efforts. Citation Format: David William Draper, Yewei Xing, Scott Wise. NK cell ADCC assays: Leveraging flow cytometry and reporter cell lines for enhanced biological relevance and throughput [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 83.

Efbalropendekin Alfa enhances human natural killer cell cytotoxicity against tumor cell lines in vitro.

IL-15 has shown preclinical activity by enhancing the functional maturation of natural killer (NK) cells. Clinical evaluation of the potential anticancer activity of most cytokines, including IL-15, has been limited by low tolerability and rapid in vivo clearance. Efbalropendekin Alfa (XmAb24306) is a soluble IL15/IL15-receptor alpha heterodimer complex fused to a half-life extended Fc domain (IL15/IL15Rα-Fc), engineered with mutations to reduce IL-15 affinity for CD122. Reduced affinity drives lower potency, leading to prolonged pharmacodynamic response in cynomolgus monkeys. We show that in vitro, human NK cells treated with XmAb24306 demonstrate enhanced cytotoxicity against various tumor cell lines. XmAb24306-treated NK cells also exhibit enhanced killing of 3D colorectal cancer spheroids. Daratumumab (dara), a monoclonal antibody (mAb) that targets CD38 results in antibody-dependent cellular cytotoxicity (ADCC) of both multiple myeloma (MM) cells and NK cells. Addition of XmAb24306 increases dara-mediated NK cell ADCC against various MM cell lines in vitro. Because NK cells express CD38, XmAb24306 increases dara-mediated NK cell fratricide, but overall does not negatively impact the ADCC activity against a MM cell line likely due to increased NK cell activity of the surviving cells. These data show that XmAb24306 increases direct and ADCC-mediated human NK cell cytotoxicity in vitro.

Abstract 1306: Primary NK cells and luciferase expressing reporter cell lines for use in developing ADCC assays for immuno-oncology drug screening

Abstract Immuno-oncology is one of the fastest growing fields in oncology, and cancer immunotherapy in recent years represents a milestone in the treatment of cancer. Natural killer (NK) cells are potent innate effectors capable of targeting and killing virally infected and malignant cells. The use of monoclonal antibodies (mAbs) targeting tumor antigens triggers antibody-dependent cellular cytotoxicity (ADCC) by NK cells, which has shown prominent clinical efficacy in clearing tumors in cancer patients. Therefore, the development of tumor cell targeting mAbs and biologics dictate a clear need for human cell-based models to evaluate antibody efficacy. In this study, human PBMCs and purified NK cells from healthy donors are used to develop an ADCC assay. The NK cells purified from PBMCs are >90% CD45+ CD56+, express high levels of CD16, and NK activation markers such NKG2A, KIR2DL1, NKp44 upon activation. The activated NK cells exhibit both strong direct and antibody-dependent cytotoxicity. Genotyping for FcγRIIIa receptor F and V variant is also performed for cells isolated from different donors, which is the genetic polymorphism that affects ADCC response. In addition, we employ a portfolio of luciferase reporter tumor cell lines to evaluate NK cell direct killing and ADCC targeted killing. These include K562, Wil2S, BT474, A431, A375 parental, and CRISPR edited A375 KRAS mutant cell lines engineered to express luc2 reporter. The commonly targeted cell surface markers, such as CD20, Her2, and EGFR, are highly expressed within this panel of target tumor cell lines. We validate the ADCC assay system through testing the efficacy for some of the well-known mAb biologics such as anti-CD20, anti-HER2, and anti-EGFR. After co-culture of activated primary NK cells with luciferase reporter target cell lines and the addition of dilutions of ADCC and isotype control antibodies, we are able to show target cell specific and dose-dependent killing effects. The luciferase reporter provides great convenience in measuring target cell killing without having to use radioactive 51Cr release assay or pre-label the cells with calcein. This data demonstrates the utility of primary NK cells along with a portfolio of well characterized luciferase reporter tumor cell line to develop “custom” designed ADCC assays for studying NK cell immune response and screening for biological drugs for cancer immunotherapy. Citation Format: Haiyun Liu, Brian Della Fera, John Foulke, Luping Chen, Fang Tian. Primary NK cells and luciferase expressing reporter cell lines for use in developing ADCC assays for immuno-oncology drug screening [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1306.

Low number of KIR ligands in lymphoma patients favors a good rituximab-dependent NK cell response

ABSTRACT The antibody-dependent cellular cytotoxicity (ADCC) effector function of natural killer (NK) cells is one of the known mechanisms of action for rituximab-based anti-cancer immunotherapy. Inhibition of the ADCC function of NK cells through interactions between inhibitory killer cell immunoglobulin-like receptors (KIRs) and HLA class I ligands is associated with resistance of cancers to rituximab. In this study, we deeply investigated the impact of KIR, HLA class I, and CD16 genotypes on rituximab-dependent NK cell responses in both an in vitro cellular model from healthy blood donors and ex vivo rituximab-treated non-Hodgkin lymphoma (NHL) patients. We highlight that an HLA environment with limited KIR ligands is beneficial to promoting a higher frequency of KIR+ NK cells including both educated and uneducated NK cells, two NK cell compartments that demonstrate higher rituximab-dependent degranulation than KIR− NK cells. In contrast, a substantial KIR ligand environment favors a higher frequency of poorly effective KIR− NK cells and numerous functional KIR/HLA inhibitions of educated KIR+ NK cells. These phenomena explain why NHL patients with limited KIR ligands respond better to rituximab. In this HLA environment, CD16 polymorphism appears to have a collateral effect. Furthermore, we show the synergic effect of KIR2DS1, which strongly potentiates NK cell ADCC from C2− blood donors against C2+ target cells. Taken together, these results pave the way for stronger prediction of rituximab responses for NHL patients. HLA class I typing and peripheral blood KIR+ NK cell frequency could be simple and useful markers for predicting rituximab response.

Considerations of Antibody Geometric Constraints on NK Cell Antibody Dependent Cellular Cytotoxicity.

It has been well-established that antibody isotype, glycosylation, and epitope all play roles in the process of antibody dependent cellular cytotoxicity (ADCC). For natural killer (NK) cells, these phenotypes are linked to cellular activation through interaction with the IgG receptor FcγRIIIa, a single pass transmembrane receptor that participates in cytoplasmic signaling complexes. Therefore, it has been hypothesized that there may be underlying spatial and geometric principles that guide proper assembly of an activation complex within the NK cell immune synapse. Further, synergy of antibody phenotypic properties as well as allosteric changes upon antigen binding may also play an as-of-yet unknown role in ADCC. Understanding these facets, however, remains hampered by difficulties associated with studying immune synapse dynamics using classical approaches. In this review, I will discuss relevant NK cell biology related to ADCC, including the structural biology of Fc gamma receptors, and how the dynamics of the NK cell immune synapse are being studied using innovative microscopy techniques. I will provide examples from the literature demonstrating the effects of spatial and geometric constraints on the T cell receptor complex and how this relates to intracellular signaling and the molecular nature of lymphocyte activation complexes, including those of NK cells. Finally, I will examine how the integration of high-throughput and “omics” technologies will influence basic NK cell biology research moving forward. Overall, the goal of this review is to lay a basis for understanding the development of drugs and therapeutic antibodies aimed at augmenting appropriate NK cell ADCC activity in patients being treated for a wide range of illnesses.

Natural Killer (NK) Cells: The Missing Link between Antibody-Mediated Rejection (ABMR) and Chronic Lung Allograft Dysfunction (CLAD)?

The long-term success of lung transplantation (LTx) is limited by CLAD. The complement-independent pathway of ABMR, driven by antibody-dependent cellular cytotoxicity (ADCC) may contribute to CLAD. ADCC is mediated through the CD16 Fc receptor expressed on NK cells, however a role for different NK cell subsets in mediating ABMR is yet to be elucidated. In this pilot study, we investigated whether the presence of donor-specific antibodies (DSA) following LTx effects NK cell ADCC and whether particular NK cell subsets exhibited superior ADCC activity. Peripheral blood mononuclear cells (PBMC) were isolated from LTx recipients at 3 and 12-months post-LTx. NK cell ADCC activity (degranulation (CD107a) and the production of cytokines from PBMC (interferon gamma (IFN-γ) and tumor necrosis alpha (TNF-α))) was measured by flow cytometry following antibody-dependent activation (ADA). The detection of anti-human leukocyte antigen (HLA) antibodies at the same time points was determined by Luminex. LTx recipients were classified as DSA positive (DSA+, presence of anti-donor HLA antibodies, n=12), anti-HLA antibody positive (HLA+, presence of anti-HLA antibodies but not to donor HLA, n=12) or no HLA antibodies (Ab-, no anti-HLA antibodies detected, n=7). Surprisingly, a higher proportion of NK cells expressed the activating receptor NKG2C in the DSA+ group (p=0.0078). Furthermore, NKG2C+ NK cells isolated from recipients with HLA antibodies were significantly more activated than NKG2A+ cells. Following ADA, a higher proportion of NKG2C+ NK cells produced cytokines in DSA+ (IFNγ, p=0.0095) and HLA+ (IFNγ: p=0.0317; TNFα: p=0.0159) recipients, compared to NKG2A+ cells. In addition, CD16 expression was more down-regulated following ADA in DSA+ recipients (p=0.0084). Our data shows that the presence of DSA impacts on the phenotype and function of NK cells following LTx. Moreover, as previous research has shown an association between NKG2C expression, cytomegalovirus (CMV) infection and CLAD, our study potentially provides a missing link between CMV infection and CLAD. Future confirmation of NKG2C+ NK cells as mediators of ABMR will lead to development of targeted diagnostic criteria and specific therapies to offer early therapeutic interventions to prevent CLAD, thereby improving LTx outcomes.

Reactive oxygen species induced by therapeutic CD20 antibodies inhibit natural killer cell-mediated antibody-dependent cellular cytotoxicity against primary CLL cells

The antibody-dependent cellular cytotoxicity (ADCC) of natural killer (NK) cells is assumed to contribute to the clinical efficacy of monoclonal antibodies (mAbs) in chronic lymphocytic leukemia (CLL) and other hematopoietic malignancies of B cell origin. We sought to determine whether reactive oxygen species (ROS)-producing monocytes regulate the ADCC of NK cells against primary CLL cells using anti-CD20 as the linking antibody. The monoclonal CD20 antibodies rituximab and ofatumumab were found to trigger substantial release of ROS from monocytes. Antibody-exposed monocytes induced NK cell apoptosis and restricted NK cell-mediated ADCC against autologous CLL cells. The presence of inhibitors of ROS formation and scavengers of ROS preserved NK cell viability and restored NK cell-mediated ADCC against primary CLL cells. We propose that limiting the antibody-induced induction of immunosuppressive ROS may improve the anti-leukemic efficacy of anti-CD20 therapy in CLL.

Preclinical Evaluation of CSL362/JNJ-56022473 in Combination with Decitabine or Azacitidine in in Vitro Assays

Acute myeloid leukemia is a heterogeneous clonal disorder characterized by abnormal differentiation and unregulated proliferation of hematopoietic progenitor cells (blast), leading to defects in hematopoiesis. Accumulating evidence has implicated leukemic stem cells (LSCs) as the main cause for perpetuation of the disease based on their profile to rapidly give rise to proliferating blasts, resistance to chemotherapeutics, and ability to self-renew. CD123 (IL-3α) has been demonstrated to be expressed at high levels on LSCs and AML blasts compared to normal hematopoietic progenitor cells (Jordon et al Leukemia 2000), providing a potential strategy to target and eliminate AML cells.CSL362, a humanized monoclonal antibody that specifically targets CD123, was engineered to have increased affinity for CD16 on natural killer (NK) cells, leading to an enhanced ability to activate NK cell antibody-dependent cellular cytotoxicity (ADCC) against CD123-positive cells (Busfield et al Leukemia 2014). JNJ-56022473 is a CSL362 variant generated from a new line and has highly similar biochemical, biophysical, and biological properties to CSL362.NK cells are an integral part of the innate immune response to AML cells, and their activity is determined by the balance of activating and inhibitory receptor stimulation (Lanier Ann Rev Immunol 2005). Decitabine and azacitidine, DNA-hypomethylating agents, have been shown to differentially modulate the expression of activating and inhibitory receptors on NK cells at physiologically used doses (Kopp et al Mol Immunol 2013, Schonefeldt et al Blood Cancer J 2013). Decitabine and azacitidine can also activate key epigenetically silenced pathways in AML cells, leading to an arrest of AML cell proliferation. We evaluated the effects of decitabine and azacitidine on CD123 expression and CSL362-mediated cytotoxicity in the TF-1 AML cell line and on NK cell activation in human peripheral blood mononuclear cells (PBMCs).To assess the effect of decitabine and azacitidine on CD123 expression and NK cell activation, 200nM of each compound was incubated with cells under various conditions. CD123 expression in treated TF-1 cells was quantitated by fluorescence-activated cell sorting, where a significant increase in CD123 expression was detected with the 3 and 5 day treatments for decitabine (p<0.001) and with the 5 day treatment for azacitidine (p<0.05). Decitabine and azacitidine treatment increased expression of the NK cell activating receptors NKG2D+ (p<0.001[decitabine] and p<0.005 [azacitidine]) and NKp46+ (p<0.001 [decitabine] and P =0.6 [azacitidine]) on PBMCs with the 5 day treatment schedule but did not affect the expression of the NK cell inhibitory receptor, KIR. Treatment with azacitidine (200nM and 1µM) reduced NK cell viability (p<0.001) compared to decitabine and also significantly downregulated IFN-gamma production (p<0.001).The ability of decitabine and azacitidine to increase expression of CD123 and NK cell activating receptors suggests that the compounds may potentiate the ADCC profile of CSL362/JNJ-56022473. TF-1 cells and PBMCs were pretreated with 200nM of each compound under different dosing regimens followed by ADCC assay with CSL362/JNJ-56022473. The percentage of specific lysis was significantly enhanced in the 5 day treatment with decitabine (66.45% lysis compared to control [32.80%]; p<0.005). In contrast, azacitidine reduced JNJ-56022473-mediated cell lysis (22.71% compared to control [30.96%]; p<0.005) with the 5 day treatment. In summary, decitabine and azacitidine pretreatment stimulated the expression of CD123 in TF-1 cells and NK cell activating receptors, NKG2D+ and NKp46+. The combination of decitabine and CSL362 increased CSL362-induced ADCC activity in TF-1 cells. In contrast, azacitidine inhibited CSL362-mediated ADCC activity, downregulated IFN-gamma production, and reduced NK cell viability. DisclosuresSyed:Janssen Research & Development at Johnson & Johnson: Employment. Pietsch:Janssen Research & Development at Johnson & Johnson: Employment. Axel:Janssen: Employment. Forslund:Janssen Research & Development at Johnson & Johnson: Employment. Sasser:Janssen Pharmaceuticals: Employment. Salvati:Janssen Research & Development at Johnson & Johnson: Employment.

Generation and Preclinical Characterization of an NKp80-Fc Fusion Protein for Redirected Cytolysis of Natural Killer (NK) Cells against Leukemia

The capacity of natural killer (NK) cells to mediate Fc receptor-dependent effector functions, such as antibody-dependent cellular cytotoxicity (ADCC), largely contributes to their clinical application. Given that activation-induced C-type lectin (AICL), an identified ligand for the NK-activating receptor NKp80, is frequently highly expressed on leukemia cells, the lack of therapeutic AICL-specific antibodies limits clinical application. Here we explore a strategy to reinforce NK anti-leukemia reactivity by combining targeting AICL-expressing leukemia cells with the induction of NK cell ADCC using NKp80-Fc fusion proteins. The NKp80-Fc fusion protein we generated bound specifically to leukemia cells in an AICL-specific manner. Cell binding assays between NK and leukemia cells showed that NKp80-Fc significantly increased NK target cell conjugation. In functional analyses, treatment with NKp80-Fc clearly induced the ADCC effect of NK cells. NKp80-Fc not only promoted NK-mediated leukemia cell apoptosis in the early stage of cell conjugation but also enhanced NK cell degranulation and cytotoxicity activity in the late stage. The bifunctional NKp80-Fc could redirect NK cells toward leukemia cells and triggered NK cell killing in vitro. Moreover, NKp80-Fc enhanced the lysis of NK cells against tumors in leukemia xenograft non-obese diabetic/severe combined immunodeficiency mice. Taken together, our results demonstrate that NKp80-Fc potently amplifies NK cell anti-leukemia effects in vitro and in vivo through induction of the NK cell ADCC effect. This method could potentially be useful for molecular targeted therapy, and the fusion proteins may be a promising drug for immunotherapy of leukemia.

An Fc-optimized NKG2D-immunoglobulin G fusion protein for induction of natural killer cell reactivity against leukemia.

Recruitment of Fc-receptor-bearing effector cells, such as natural killer (NK) cells, is a feature critical for the therapeutic success of antitumor antibodies and can be improved by the modifications of an antibody's Fc part. The various ligands of the activating immunoreceptor NKG2D, NKG2DL) are selectively expressed on malignant cells including leukemia. We here took advantage of the tumor-associated expression of NKG2DL for targeting leukemic cells by NKG2D-immunoglobulin G (IgG)1 fusion proteins containing modified Fc parts. Compared to NKG2D-Fc containing a wild-type Fc part (NKG2D-Fc-WT), our mutants (S239D/I332E and E233P/L234V/L235A/ΔG236/A327G/A330S) displayed highly enhanced (NKG2D-Fc-ADCC) and abrogated (NKG2D-Fc-KO) affinity to the NK cell Fc receptor, respectively. Functional analyses with allogenic as well as autologous NK cells and primary malignant cells of leukemia patients revealed that NKG2D-Fc-KO significantly reduced NK reactivity by blocking immunostimulatory NKG2D-NKG2DL interaction. NKG2D-Fc-WT already enhanced antileukemia reactivity by inducing antibody-dependent cellular cytotoxicity (ADCC) with NKG2D-Fc-ADCC mediating significantly stronger effects. Parallel application of NKG2D-Fc-ADCC with Rituximab caused additive effects in lymphoid leukemia. In line with the tumor-associated expression of NKG2DL, no NK cell ADCC against resting healthy blood cells was induced. Thus, NKG2D-Fc-ADCC potently enhances NK antileukemia reactivity despite the inevitable reduction of activating signals upon binding to NKG2DL and may constitute an attractive means for immunotherapy of leukemia.

Way to go to exploit NK cells' versatile talents for cancer immunotherapy.

Way to go to exploit NK cells' versatile talents for cancer immunotherapy.

Intravenous Immunoglobulins Suppress Antibody-Dependent Effector Functions of Human Peripheral Blood Cells

RationaleSeveral studies have shown the importance of self-reactive antibodies in the maintenance of autoimmune diseases. Therefore, we asked whether IGIV, which is therapeutically effective in some of those diseases, directly modulates antibody-mediated effector functions.MethodsWe used a human in vitro system to analyze potential modulatory effects of IGIV on effector functions in antibody-dependent cellular cytotoxicity (ADCC). Human peripheral blood mononuclear cells (PBMC) from 47 healthy volunteers were pre-incubated with IGIV and then added to human breast cancer cells (SK-BR3) opsonized with a specific antibody. The cytotoxic damage to SK-BR3 cells was determined by measuring lactate dehydrogenase release into supernatants. IGIV-mediated effects on viability and Fc gamma receptor (FcγR) expression of PBMC were analyzed by flow cytometry.ResultsPre-incubation of PBMC with IGIV for 48h resulted in a marked inhibition of ADCC, ranging from 15% to 74% (mean 42%) which could not be mimicked with human monoclonal IgG1 and IgG2 antibodies. Flow cytometric analysis indicated that IGIV induced natural killer (NK) cell death, which significantly correlated with ADCC inhibition. The IGIV-induced decrease in NK cell viability was not triggered by FcγR ligation since the addition of FcγR blocking antibodies could not prevent cell death induction. Furthermore, IGIV enriched for sialic acid bearing glycans by lectin affinity chromatography with Sambucus nigra agglutinin showed no differences in the effects on NK cell viability and ADCC compared with non-enriched IGIV.ConclusionsIGIV modulates antibody-dependent effector functions of human immune cells, which could contribute to the modulatory activities of IGIV in inflammatory and autoimmune diseases. RationaleSeveral studies have shown the importance of self-reactive antibodies in the maintenance of autoimmune diseases. Therefore, we asked whether IGIV, which is therapeutically effective in some of those diseases, directly modulates antibody-mediated effector functions. Several studies have shown the importance of self-reactive antibodies in the maintenance of autoimmune diseases. Therefore, we asked whether IGIV, which is therapeutically effective in some of those diseases, directly modulates antibody-mediated effector functions. MethodsWe used a human in vitro system to analyze potential modulatory effects of IGIV on effector functions in antibody-dependent cellular cytotoxicity (ADCC). Human peripheral blood mononuclear cells (PBMC) from 47 healthy volunteers were pre-incubated with IGIV and then added to human breast cancer cells (SK-BR3) opsonized with a specific antibody. The cytotoxic damage to SK-BR3 cells was determined by measuring lactate dehydrogenase release into supernatants. IGIV-mediated effects on viability and Fc gamma receptor (FcγR) expression of PBMC were analyzed by flow cytometry. We used a human in vitro system to analyze potential modulatory effects of IGIV on effector functions in antibody-dependent cellular cytotoxicity (ADCC). Human peripheral blood mononuclear cells (PBMC) from 47 healthy volunteers were pre-incubated with IGIV and then added to human breast cancer cells (SK-BR3) opsonized with a specific antibody. The cytotoxic damage to SK-BR3 cells was determined by measuring lactate dehydrogenase release into supernatants. IGIV-mediated effects on viability and Fc gamma receptor (FcγR) expression of PBMC were analyzed by flow cytometry. ResultsPre-incubation of PBMC with IGIV for 48h resulted in a marked inhibition of ADCC, ranging from 15% to 74% (mean 42%) which could not be mimicked with human monoclonal IgG1 and IgG2 antibodies. Flow cytometric analysis indicated that IGIV induced natural killer (NK) cell death, which significantly correlated with ADCC inhibition. The IGIV-induced decrease in NK cell viability was not triggered by FcγR ligation since the addition of FcγR blocking antibodies could not prevent cell death induction. Furthermore, IGIV enriched for sialic acid bearing glycans by lectin affinity chromatography with Sambucus nigra agglutinin showed no differences in the effects on NK cell viability and ADCC compared with non-enriched IGIV. Pre-incubation of PBMC with IGIV for 48h resulted in a marked inhibition of ADCC, ranging from 15% to 74% (mean 42%) which could not be mimicked with human monoclonal IgG1 and IgG2 antibodies. Flow cytometric analysis indicated that IGIV induced natural killer (NK) cell death, which significantly correlated with ADCC inhibition. The IGIV-induced decrease in NK cell viability was not triggered by FcγR ligation since the addition of FcγR blocking antibodies could not prevent cell death induction. Furthermore, IGIV enriched for sialic acid bearing glycans by lectin affinity chromatography with Sambucus nigra agglutinin showed no differences in the effects on NK cell viability and ADCC compared with non-enriched IGIV. ConclusionsIGIV modulates antibody-dependent effector functions of human immune cells, which could contribute to the modulatory activities of IGIV in inflammatory and autoimmune diseases. IGIV modulates antibody-dependent effector functions of human immune cells, which could contribute to the modulatory activities of IGIV in inflammatory and autoimmune diseases.

NK Cell Function and Antibodies Mediating ADCC in HIV-1-Infected Viremic and Controller Patients

Natural killer (NK) cells have been suggested to play a protective role in HIV disease progression. One potent effector mechanism of NK cells is antibody-dependent cellular cytotoxicity (ADCC) mediated by antiviral antibodies binding to the FcγRIIIa receptor (CD16) on NK cells. We investigated NK cell-mediated ADCC function and the presence of ADCC antibodies in plasma from 20 HIV-1-infected patients and 10 healthy donors. The HIV-positive patients were divided into two groups: six who controlled viremia for at least 8 y without treatment (controllers), and 14 who were persistently viremic and not currently on treatment. Plasma from both patient groups induced NK cell IFN-γ expression and degranulation in response to HIV-1 envelope (Env) gp140-protein-coated cells. Patient antibodies mediating ADCC were largely directed towards the Env V3 loop, as identified by a gp140 protein lacking the V3 loop. Interestingly, in two controllers ADCC-mediating antibodies were more broadly directed to other parts of Env. A high viral load in patients correlated with decreased ADCC-mediated cytolysis of gp140-protein-coated target cells. NK cells from both infected patients and healthy donors degranulated efficiently in the presence of antibody-coated HIV-1-infected Jurkat cells. In conclusion, the character of ADCC-mediating antibodies differed in some controllers compared to viremic patients. NK cell ADCC activity is not compromised in HIV-infected patients.

Lenalidomide Enhances Natural Killer Cell and Monocyte-Mediated Antibody-Dependent Cellular Cytotoxicity of Rituximab-Treated CD20+ Tumor Cells

Lenalidomide has significant activity in myelodysplastic syndromes, multiple myeloma, and non-Hodgkin's lymphoma (NHL). In previous studies, natural killer (NK) cell expansion by lenalidomide was shown to enhance the cytotoxic effect of rituximab. This study assessed the ability of lenalidomide to enhance antibody-dependent cellular cytotoxicity (ADCC) in rituximab-treated NHL cell lines and primary tumor cells from patients with B-cell chronic lymphocytic leukemia (B-CLL) in vitro. An in vitro ADCC system was used to assess the ability of lenalidomide to enhance human NK cell and monocyte function in response to rituximab. Lenalidomide directly enhanced IFN-gamma production via Fc-gamma receptor-mediated signaling in response to IgG. It was also a potent enhancer of NK cell-mediated and monocyte-mediated tumor cell ADCC for a variety of rituximab-treated NHL cell lines in vitro, an effect that was dependent on the presence of antibody and either interleukin-2 or interleukin-12. Lenalidomide also enhanced the ability of NK cells to kill primary tumor cells derived from three patients with B-CLL who have been treated previously with fludarabine plus cyclophosphamide. Enhanced NK cell ADCC was associated with enhanced granzyme B and Fas ligand expression and could be inhibited by a granzyme B inhibitor and partially inhibited by antibody to FasL. Enhanced NK cell Fc-gamma receptor signaling is associated with enhanced phosphorylated extracellular signal-related kinase levels leading to enhanced effector function. These findings suggest that lenalidomide has the potential to enhance the rituximab-induced killing of NHL cell lines and primary B-cell chronic lymphocytic leukemia cells via a NK cell-mediated and monocyte-mediated ADCC mechanism in vitro, providing a strong rationale for the combination of lenalidomide with IgG1 antibodies to target tumor-specific antigens in patients with cancer.

The Activation of Natural Killer Cell Effector Functions by Cetuximab-Coated, Epidermal Growth Factor Receptor–Positive Tumor Cells is Enhanced By Cytokines

Natural killer (NK) cells express an activating Fc receptor (FcgammaRIIIa) that mediates antibody-dependent cellular cytotoxicity (ADCC) and production of immune modulatory cytokines in response to antibody-coated targets. Cetuximab is a therapeutic monoclonal antibody directed against the HER1 antigen. We hypothesized that the NK cell response to cetuximab-coated tumor cells could be enhanced by the administration of NK cell-stimulatory cytokines. Human NK cells stimulated with cetuximab-coated tumor cells and interleukin-2 (IL-2), IL-12, or IL-21 were assessed for ADCC and secretion of IFN-gamma and T cell-recruiting chemokines. IL-21 and cetuximab were given to nude mice bearing HER1-positive xenografts. Stimulation of human NK cells with cetuximab-coated tumor cells and IL-2, IL-12, or IL-21 resulted in 3-fold to 10-fold higher IFN-gamma production than was observed with either agent alone. NK cell-derived IFN-gamma significantly enhanced monocyte ADCC against cetuximab-coated tumor cells. Costimulated NK cells also secreted elevated levels of chemokines (IL-8, macrophage inflammatory protein-1alpha, and RANTES) that could direct the migration of naive and activated T cells. IL-2, IL-12, and IL-21 enhanced NK cell ADCC against tumor cells treated with cetuximab. The combination of cetuximab, trastuzumab (an anti-HER2 monoclonal antibody), and IL-21 mediated greater NK cell cytokine secretion and ADCC than any agent alone. Furthermore, administration of IL-21 enhanced the effects of cetuximab in a murine tumor model. These results show that cetuximab-mediated NK cell activity can be significantly enhanced in the presence of NK cell-stimulatory cytokines. These factors, therefore, may be effective adjuvants to administer, in combination with cetuximab, to patients with HER1-positive malignancies.

Natural killer cell activity in long-term survivors of testicular cancer. Influence of cytostatic therapy and initial stage of disease.

Patients with testicular cancer can be cured by cisplatin-based chemotherapy in many cases. Thus, concern about possible late toxicities of treatment is warranted. In this investigation, the absolute number of natural killer (NK) cells according to their CD56+ phenotype, NK cell activity, and antibody dependent cellular cytotoxicity (ADCC) were investigated in 29 patients with seminomas or nonseminomatous germ cell tumors (NSGCT) a median of 31 months (range, 5-73 months) after termination of chemotherapeutic treatment. No difference in the absolute number of NK cells, NK cell activity, and ADCC was found between patients with testicular cancer after either standard polychemotherapy consisting of bleomycin, etoposide, and cisplatin (BEP) or monotherapy with carboplatin and healthy control subjects. When patients were analyzed further using multivariate analysis, a significant (P < 0.05) detrimental influence of BEP polychemotherapy versus carboplatin monotherapy on NK cell activity was found. Moreover, NK cell activity also depended significantly (P < 0.05) on the time elapsed after chemotherapy was administered, but normalized with time. Because the absolute number of NK cells was not affected, is was assumed that polychemotherapy induced a functional defect. In a subanalysis of patients with NSGCTs, metastases at diagnosis resulted in a significant (p < 0.05) and persistent stimulation of NK cell activity but not of ADCC. Cytostatic chemotherapy in patients with testicular cancer did not lead to compromised lytic effector cell function as assessed by NK cell activity and ADCC. However, a short, time-dependent reduction was found that also depended on the intensity of chemotherapeutic treatment. This finding related to the observation of a long-lasting stimulus of NK cell activity by initial metastases in patients with NSGCTs.

Histaminergic regulation of antibody-dependent cellular cytotoxicity of granulocytes, monocytes, and natural killer cells

We investigated effects of the biogenic diamine histamine on antibody-dependent cellular cytotoxicity (ADCC) against autologous anti-D-coated red blood cells mediated by human granulocytes, monocytes, and natural killer (NK) cells. Effector cells were separated from peripheral blood by countercurrent centrifugal elutriation. ADCC of monocytes and neutrophilic granulocytes was suppressed by histamine. ADCC of enriched CD3-/56+ NK cells was unchanged by histamine. ADCC of NK cells was effectively inhibited by elutriated monocytes or neutrophils. Histamine completely reversed the inhibition of NK cell-mediated ADCC induced by monocytes and partly reversed the inhibition induced by neutrophils; thereby, histamine augmented ADCC of NK cells in the presence of monocytes or neutrophils. The indirect effect of histamine on ADCC of NK cells and the effect of histamine on ADCC of monocytes/neutrophils were completely antagonized by the specific H2 receptor (H2R) blocker ranitidine. We conclude that activation of H2R suppresses ADCC reactivity of monocytes/neutrophils and, concomitantly, promotes ADCC reactivity of NK cells by abrogating a phagocyte-derived, suppressive signal.