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Bauer-Smith H, Sudol ASL, Beers SA, Crispin M. Serum immunoglobulin and the threshold of Fc receptor-mediated immune activation. Biochim Biophys Acta Gen Subj 2023; 1867:130448. [PMID: 37652365 PMCID: PMC11032748 DOI: 10.1016/j.bbagen.2023.130448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Revised: 08/23/2023] [Accepted: 08/23/2023] [Indexed: 09/02/2023]
Abstract
Antibodies can mediate immune recruitment or clearance of immune complexes through the interaction of their Fc domain with cellular Fc receptors. Clustering of antibodies is a key step in generating sufficient avidity for efficacious receptor recognition. However, Fc receptors may be saturated with prevailing, endogenous serum immunoglobulin and this raises the threshold by which cellular receptors can be productively engaged. Here, we review the factors controlling serum IgG levels in both healthy and disease states, and discuss how the presence of endogenous IgG is encoded into the functional activation thresholds for low- and high-affinity Fc receptors. We discuss the circumstances where antibody engineering can help overcome these physiological limitations of therapeutic antibodies. Finally, we discuss how the pharmacological control of Fc receptor saturation by endogenous IgG is emerging as a feasible mechanism for the enhancement of antibody therapeutics.
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Affiliation(s)
- Hannah Bauer-Smith
- School of Biological Sciences, University of Southampton, Southampton SO17 1BJ, UK; Centre for Cancer Immunology, School of Cancer Sciences, University of Southampton Faculty of Medicine, Southampton SO16 6YD, UK
| | - Abigail S L Sudol
- School of Biological Sciences, University of Southampton, Southampton SO17 1BJ, UK
| | - Stephen A Beers
- Centre for Cancer Immunology, School of Cancer Sciences, University of Southampton Faculty of Medicine, Southampton SO16 6YD, UK.
| | - Max Crispin
- School of Biological Sciences, University of Southampton, Southampton SO17 1BJ, UK.
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2
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Elias S, Kol I, Kahlon S, Amore R, Zeibak M, Mevorach D, Elchalal U, Zelig O, Mandelboim O. Anti-RhD antibody therapy modulates human natural killer cell function. Haematologica 2021; 106:1846-1856. [PMID: 32467141 PMCID: PMC8252960 DOI: 10.3324/haematol.2019.238097] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Indexed: 12/13/2022] Open
Abstract
Anti-RhD antibodies are widely used in clinical practice to prevent immunization against RhD, principally in hemolytic disease of the fetus and newborn. Intriguingly, this disease is induced by production of the very same antibodies when an RhD negative woman is pregnant with an RhD positive fetus. Despite over five decades of use, the mechanism of this treatment is, surprisingly, still unclear. Here we show that anti-RhD antibodies induce human natural killer (NK) cell degranulation. Mechanistically, we demonstrate that NK cell degranulation is mediated by binding of the Fc segment of anti-RhD antibodies to CD16, the main Fcγ receptor expressed on NK cells. We found that this CD16 activation is dependent upon glycosylation of the anti-RhD antibodies. Furthermore, we show that anti-RhD antibodies induce NK cell degranulation in vivo in patients who receive this treatment prophylactically. Finally, we demonstrate that the anti-RhD drug KamRho enhances the killing of dendritic cells. We suggest that this killing leads to reduced activation of adaptive immunity and may therefore affect the production of anti-RhD antibodies
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Affiliation(s)
- Shlomo Elias
- The Hebrew University Hadassah Medical School, Jerusalem, Israel
| | - Inbal Kol
- The Hebrew University Hadassah Medical School, Jerusalem, Israel
| | - Shira Kahlon
- The Hebrew University Hadassah Medical School, Jerusalem, Israel
| | - Rajaa Amore
- Department of Hematology, Hadassah - Hebrew University Medical Center, Jerusalem, Israel
| | - Mariam Zeibak
- Department of Hematology, Hadassah - Hebrew University Medical Center, Jerusalem, Israel
| | - Dror Mevorach
- Department of Hematology, Hadassah - Hebrew University Medical Center, Jerusalem, Israel
| | - Uriel Elchalal
- Dept. of Obstetrics and Gynecology, Hadassah - Hebrew University Medical Center, Jerusalem, Israel
| | - Orly Zelig
- Department of Hematology, Hadassah - Hebrew University Medical Center, Jerusalem, Israel
| | - Ofer Mandelboim
- The Hebrew University Hadassah Medical School, Jerusalem, Israel
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Signaling by Fyn-ADAP via the Carma1-Bcl-10-MAP3K7 signalosome exclusively regulates inflammatory cytokine production in NK cells. Nat Immunol 2013; 14:1127-36. [PMID: 24036998 PMCID: PMC3855032 DOI: 10.1038/ni.2708] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Accepted: 08/09/2013] [Indexed: 11/29/2022]
Abstract
Inflammation is a critical component of the immune response. However, acute or chronic inflammation can be highly destructive. Uncontrolled inflammation forms the basis for allergy, asthma, and multiple autoimmune disorders. Here, we identify a signaling pathway that is exclusively responsible for inflammatory cytokine production but not for cytotoxicity. Recognition of H60+ or CD137L+ tumor cells by murine NK cells led to efficient cytotoxicity and inflammatory cytokine production. Both of these effector functions required Lck, Fyn, PI(3)K-p85α, PI(3)K-p110δ, and PLC-γ2. However, the complex of Fyn and the adapter ADAP exclusively regulated inflammatory cytokine production but not cytotoxicity in NK cells. This unique function of ADAP required a Carma1-Bcl10-MAP3K7 signaling axis. Our results identify molecules that can be targeted to regulate inflammation without compromising NK cell cytotoxicity.
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4
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König S, Nimtz M, Scheiter M, Ljunggren HG, Bryceson YT, Jänsch L. Kinome analysis of receptor-induced phosphorylation in human natural killer cells. PLoS One 2012; 7:e29672. [PMID: 22238634 PMCID: PMC3251586 DOI: 10.1371/journal.pone.0029672] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Accepted: 12/01/2011] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND Natural killer (NK) cells contribute to the defense against infected and transformed cells through the engagement of multiple germline-encoded activation receptors. Stimulation of the Fc receptor CD16 alone is sufficient for NK cell activation, whereas other receptors, such as 2B4 (CD244) and DNAM-1 (CD226), act synergistically. After receptor engagement, protein kinases play a major role in signaling networks controlling NK cell effector functions. However, it has not been characterized systematically which of all kinases encoded by the human genome (kinome) are involved in NK cell activation. RESULTS A kinase-selective phosphoproteome approach enabled the determination of 188 kinases expressed in human NK cells. Crosslinking of CD16 as well as 2B4 and DNAM-1 revealed a total of 313 distinct kinase phosphorylation sites on 109 different kinases. Phosphorylation sites on 21 kinases were similarly regulated after engagement of either CD16 or co-engagement of 2B4 and DNAM-1. Among those, increased phosphorylation of FYN, KCC2G (CAMK2), FES, and AAK1, as well as the reduced phosphorylation of MARK2, were reproducibly observed both after engagement of CD16 and co-engagement of 2B4 and DNAM-1. Notably, only one phosphorylation on PAK4 was differentally regulated. CONCLUSIONS The present study has identified a significant portion of the NK cell kinome and defined novel phosphorylation sites in primary lymphocytes. Regulated phosphorylations observed in the early phase of NK cell activation imply these kinases are involved in NK cell signaling. Taken together, this study suggests a largely shared signaling pathway downstream of distinct activation receptors and constitutes a valuable resource for further elucidating the regulation of NK cell effector responses.
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Affiliation(s)
- Sebastian König
- Department of Molecular Structural Biology, Helmholtz-Zentrum für Infektionsforschung, Braunschweig, Germany
| | - Manfred Nimtz
- Department of Molecular Structural Biology, Helmholtz-Zentrum für Infektionsforschung, Braunschweig, Germany
| | - Maxi Scheiter
- Department of Molecular Structural Biology, Helmholtz-Zentrum für Infektionsforschung, Braunschweig, Germany
| | - Hans-Gustaf Ljunggren
- Center for Infectious Medicine, Department of Medicine, Karolinska Institutet, Karolinska University Hospital Huddinge, Stockholm, Sweden
| | - Yenan T. Bryceson
- Center for Infectious Medicine, Department of Medicine, Karolinska Institutet, Karolinska University Hospital Huddinge, Stockholm, Sweden
| | - Lothar Jänsch
- Department of Molecular Structural Biology, Helmholtz-Zentrum für Infektionsforschung, Braunschweig, Germany
- * E-mail:
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5
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Differential requirements for CD45 in NK-cell function reveal distinct roles for Syk-family kinases. Blood 2011; 117:3087-95. [PMID: 21245479 DOI: 10.1182/blood-2010-06-292219] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The protein tyrosine phosphatase CD45 is an important regulator of Src-family kinase activity. We found that in the absence of CD45, natural killer (NK) cells are defective in protecting the host from mouse cytomegalovirus infection. We show that although CD45 is necessary for all immunoreceptor tyrosine-based activation motif (ITAM)-specific NK-cell functions and processes such as degranulation, cytokine production, and expansion during viral infection, the impact of CD45 deficiency on ITAM signaling differs depending on the downstream function. CD45-deficient NK cells are normal in their response to inflammatory cytokines when administered ex vivo and in the context of viral infection. Syk and ζ chain-associated protein kinase 70 (Zap70) are thought to play redundant roles in transmitting ITAM signals in NK cells. We show that Syk, but not Zap70, controls the remaining CD45-independent, ITAM-specific NK-cell functions, demonstrating a functional difference between these 2 Syk-kinase family members in primary NK cells.
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Delay of LPS-induced acute lung injury resolution by soluble immune complexes is neutrophil dependent. Shock 2009; 32:276-85. [PMID: 19106808 DOI: 10.1097/shk.0b013e31819962b2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The pathophysiological role of soluble immune complexes (SICXs) and its relationship with neutrophils were investigated in LPS-induced acute lung injury (ALI) animal model (Sprague-Dawley rat) and through the in vitro studies. Results showed that LPS-induced SICX was timely related to changes of tumor necrosis factor alpha and macrophage inflammatory protein 2 (inflammatory cytokines) in bronchoalveolar lavage fluid. In vitro study showed that SICX can bind to Fc gammaR (CD64 and CD32 or CD16) to prevent the apoptosis of neutrophils. The SICX-mediated apoptosis inhibition was extracellular signal-regulated kinase (ERK) or phosphoinositide 3 kinase dependent and was interrupted by PD98059 and LY294002. In vivo, additional amount of SICX exacerbated the lung injury caused by LPS. LPS-induced lung injury and macrophage inflammatory protein 2 release, however, were prevented by CD64 and CD32 blockers (decoy antibodies). In conclusion, excessive amount of SICX in lung can act through Fc gammaRs to protect bronchoalveolar lavage fluid neutrophils from apoptosis that eventually lead to delayed resolution of ALI caused by LPS. Blockade of SICX engagement of CD32 and CD64 (with decoy antibodies) could interrupt SICX-mediated protection of neutrophils and protect lung from LPS-induced injury. The decoy antibodies may therefore have therapeutic utility in ALI.
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Gilbert C, Barat C, Cantin R, Tremblay MJ. Involvement of Src and Syk Tyrosine Kinases in HIV-1 Transfer from Dendritic Cells to CD4+T Lymphocytes. THE JOURNAL OF IMMUNOLOGY 2007; 178:2862-71. [PMID: 17312130 DOI: 10.4049/jimmunol.178.5.2862] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Dendritic cells (DCs) are considered as key mediators of the early events in HIV-1 infection at mucosal sites. Although several aspects of the complex interactions between DCs and HIV-1 have been elucidated, there are still basic questions that remain to be answered about DCs/HIV-1 interplay. In this study, we examined the contribution of nonreceptor TKs in the known ability of DCs to efficiently transfer HIV-1 to CD4(+) T cells in trans. Experiments performed with specific inhibitors of Src and Syk family members indicate that these tyrosine kinases (TKs) are participating to HIV-1 transfer from immature monocyte-derived DCs (IM-MDDCs) to autologous CD4(+) T cells. Experiments with IM-MDDCs transfected with small interfering RNAs targeting Lyn and Syk confirmed the importance of these nonreceptor TKs in HIV-1 transmission. The Src- and Syk-mediated effect on virus transfer was linked with infection of IM-MDDCs in cis-as monitored by quantifying integrated viral DNA and de novo virus production. The process of HIV-1 transmission from IM-MDDCs to CD4(+) T cells was unaffected following treatment with protein kinase C and protein kinase A inhibitors. These data suggest that Src and Syk TKs play a functional role in productive HIV-1 infection of IM-MDDCs. Additional work is needed to facilitate our comprehension of the various mechanisms underlying the exact contribution of Src and Syk TKs to this phenomenon.
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Affiliation(s)
- Caroline Gilbert
- Centre de Recherche en Infectiologie, Centre Hospitalier de l'Université Laval, and Faculté de Médecine, Université Laval, 2705 Boulevard Laurier, Quebec, Canada
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Roda JM, Parihar R, Lehman A, Mani A, Tridandapani S, Carson WE. Interleukin-21 enhances NK cell activation in response to antibody-coated targets. THE JOURNAL OF IMMUNOLOGY 2006; 177:120-9. [PMID: 16785506 DOI: 10.4049/jimmunol.177.1.120] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
NK cells express an activating FcR (FcgammaRIIIa) that mediates Ab-dependent cellular cytotoxicity and the production of immune modulatory cytokines in response to Ab-coated targets. IL-21 has antitumor activity in murine models that depends in part on its ability to promote NK cell cytotoxicity and IFN-gamma secretion. We hypothesized that the NK cell response to FcR stimulation would be enhanced by the administration of IL-21. Human NK cells cultured with IL-21 and immobilized IgG or human breast cancer cells coated with a therapeutic mAb (trastuzumab) secreted large amounts of IFN-gamma. Increased secretion of TNF-alpha and the chemokines IL-8, MIP-1alpha, and RANTES was also observed under these conditions. NK cell IFN-gamma production was dependent on distinct signals mediated by the IL-21R and the FcR and was abrogated in STAT1-deficient NK cells. Supernatants derived from NK cells that had been stimulated with IL-21 and mAb-coated breast cancer cells were able to drive the migration of naive and activated T cells in an in vitro chemotaxis assay. IL-21 also enhanced NK cell lytic activity against Ab-coated tumor cells. Coadministration of IL-21 and Ab-coated tumor cells to immunocompetent mice led to synergistic production of IFN-gamma by NK cells. Furthermore, the administration of IL-21 augmented the effects of an anti-HER2/neu mAb in a murine tumor model, an effect that required IFN-gamma. These findings demonstrate that IL-21 significantly enhances the NK cell response to Ab-coated targets and suggest that IL-21 would be an effective adjuvant to administer in combination with therapeutic mAbs.
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MESH Headings
- Adjuvants, Immunologic/administration & dosage
- Adjuvants, Immunologic/physiology
- Animals
- Antibodies, Monoclonal/metabolism
- Antibodies, Monoclonal/therapeutic use
- Antibodies, Monoclonal, Humanized
- Antineoplastic Agents/metabolism
- Antineoplastic Agents/therapeutic use
- Breast Neoplasms/immunology
- Breast Neoplasms/pathology
- Cell Line, Tumor
- Chemokines/biosynthesis
- Chemokines/physiology
- Chemotaxis, Leukocyte/immunology
- Cytotoxicity Tests, Immunologic
- Disease Models, Animal
- Female
- Humans
- Immunoglobulin G/chemistry
- Immunoglobulin G/metabolism
- Interferon-gamma/biosynthesis
- Interferon-gamma/blood
- Interleukins/administration & dosage
- Interleukins/physiology
- Killer Cells, Natural/immunology
- Killer Cells, Natural/metabolism
- Lymphocyte Activation/immunology
- Mice
- Mice, Inbred BALB C
- Neoplasm Transplantation
- Receptor, ErbB-2/immunology
- T-Lymphocyte Subsets/immunology
- Trastuzumab
- Tumor Necrosis Factor-alpha/biosynthesis
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Affiliation(s)
- Julie M Roda
- Integrated Biomedical Sciences Graduate Program, Department of Molecular Virology, Arthur G. James Comprehensive Cancer Center and Solove Research Institute, Ohio State University, Columbus, OH 43210, USA
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9
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Mota G, Moldovan I, Calugaru A, Hirt M, Kozma E, Galatiuc C, Brasoveanu L, Boltz-Nitulescu G. Interaction of human immunoglobulin G with CD16 on natural killer cells: ligand clearance, FcgammaRIIIA turnover and effects of metalloproteinases on FcgammaRIIIA-mediated binding, signal transduction and killing. Scand J Immunol 2004; 59:278-84. [PMID: 15030579 DOI: 10.1111/j.0300-9475.2004.01398.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Human natural killer (NK) cells express low-affinity Fc immunoglobulin G (IgG) receptor (FcgammaRIIIA/CD16). The binding of monomeric IgG (mIgG) and F(ab')(2) fragments of 3G8 anti-CD16 monoclonal antibody (mAb) to FcgammaRIIIA was investigated by flow cytometry. Over 90% of NK cells bound endogenous IgG, and during incubation at 37 degrees C, the FcgammaRIIIA occupancy decreased slowly. Approximately 90% of NK cells bind mIgG or F(ab')(2) fragments of 3G8 anti-CD16 mAb. The calculated half-time (T(1/2)) of in vitro mIgG dissociation from FcgammaRIIIA was 130 min. By cross-linking the mIgG ligand with F(ab')(2) fragments of anti-human IgG antibody, the T(1/2) decreases to 85 min. In kinetics study, it has been shown that (125)I-mIgG bound to FcgammaRIIIA is slowly released in the culture supernatant, maybe eluted at acid pH, or partially internalized and degraded. The binding of IgG to FcgammaRIIIA was increased by 53.8% on cells cultured in the presence of RU36156, a matrix metalloproteinase (MMP) inhibitor. Furthermore, an increase in phosphorylation of Lyn tyrosine kinase, after cross-linking of mIgG-FcgammaRIIIA complex, was observed on NK cells treated with RU36156. When the FcgammaRIIIA was occupied by mIgG, the capacity of NK cells to kill K562 target cells was decreased by RU36156, because the MMP inhibitor protects CD16 from proteolysis. Our data demonstrate that binding of mIgG to human NK cells is followed by ligand dissociation and/or internalization, enzymatic degradation and exocytosis. The RU36156 MMP inhibitor protects FcgammaRIIIA from cleavage, augments NK-cell activation and may interfere in their killing capacity.
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Affiliation(s)
- G Mota
- Center of Immunology, Institute of Virology, 285 Mihai Bravu st., 79650 Bucharest, Romania
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10
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Parihar R, Dierksheide J, Hu Y, Carson WE. IL-12 enhances the natural killer cell cytokine response to Ab-coated tumor cells. J Clin Invest 2002; 110:983-92. [PMID: 12370276 PMCID: PMC151155 DOI: 10.1172/jci15950] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The anti-tumor activity of recombinant mAb's directed against tumor cell growth receptors has generally been considered to result from direct antiproliferative effects, the induction of apoptosis, or possibly Ab-dependent cellular cytotoxicity mediated against tumor targets. However, it remains unclear to what degree these mechanisms actually aid in the clearance of Ab-coated tumor cells in vivo. We show here that NK cells secrete a distinct profile of potent immunostimulatory cytokines in response to dual stimulation with Ab-coated tumor cells and IL-12. This response could not be duplicated by costimulation with other ILs and was significantly enhanced in the presence of monocytes. Cytokine production was dependent upon synergistic signals mediated by the activating receptor for the Fc portion of IgG (FcgammaRIII) and the IL-12 receptor expressed on NK cells. Coadministration of Ab-coated tumor cells and IL-12 to BALB/c mice resulted in enhanced circulating levels of NK cell-derived cytokines with the capacity to augment anti-tumor immunity. These findings suggest that, in addition to mediating cellular cytotoxicity and apoptosis, the anti-tumor activity of mAb's might also result from activation of a potent cytokine secretion program within immune effectors capable of recognizing mAb-coated targets.
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MESH Headings
- Animals
- Antibodies, Monoclonal/pharmacology
- Antibodies, Monoclonal, Humanized
- Antineoplastic Agents/pharmacology
- DNA-Binding Proteins/physiology
- Female
- Humans
- Immunoglobulin G/therapeutic use
- Interferon-gamma/biosynthesis
- Interleukin-12/pharmacology
- Interleukin-12/therapeutic use
- Killer Cells, Natural/drug effects
- Killer Cells, Natural/immunology
- Mice
- Mice, Inbred BALB C
- Receptor, ErbB-2/analysis
- Receptors, IgG/physiology
- Receptors, Interleukin/physiology
- Receptors, Interleukin-12
- Recombinant Proteins/pharmacology
- STAT4 Transcription Factor
- Trans-Activators/physiology
- Trastuzumab
- Tumor Cells, Cultured
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Affiliation(s)
- Robin Parihar
- Department of Molecular Virology, Immunology, and Medical Genetics, The Arthur G. James Comprehensive Cancer Center, The Ohio State University College of Medicine, Columbus, Ohio 43210, USA
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11
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Parihar R, Dierksheide J, Hu Y, Carson WE. IL-12 enhances the natural killer cell cytokine response to Ab-coated tumor cells. J Clin Invest 2002. [DOI: 10.1172/jci0215950] [Citation(s) in RCA: 121] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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12
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Sulica A, Morel P, Metes D, Herberman RB. Ig-binding receptors on human NK cells as effector and regulatory surface molecules. Int Rev Immunol 2001; 20:371-414. [PMID: 11878510 DOI: 10.3109/08830180109054414] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The receptors on human natural killer 9NK cells which can specifically bind the Fc portion of immunoglobulin molecules (Fc receptors) have been extensively studied. The best known and studied Fc receptor on human NK cells is FcgammaRIIIa. Interactions of NK cells with IgG antibodies via this receptor are well known to induce a signal transduction cascade and lead to antibody-dependent cell-mediated cytotoxicity (ADCC) as well as release of various cytokines. In addition, interactions with monomeric IgG and FcgammaRIIIa have been demonstrated, which result in negative regulation of NK activity and other immunomodulatory effects. Over the past several years, it has also become increasingly appreciated that human NK cells express a variety of other Fc receptors, including FcmuR, which also can mediate effector and immunoregulatory functions. Also, a novel form of FcgammaR has been demonstrated on human NK cells, termed FcgammaRIIc. Recent molecular studies have shown considerable polymorphism in the genes for FcgammaIIc and the functional consequences are being dissected. This appears to include cross-talk between FcgammaRIIIa and at least some forms of FcgammaRIIc, which may have important functional consequences.
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Affiliation(s)
- A Sulica
- Center for Immunology, Bucharest, Romania
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13
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Affiliation(s)
- B Perussia
- Jefferson Medical College, Kimmel Cancer Institute, Philadelphia, PA 19107, USA
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14
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Abstract
CD44 is a cytotoxic triggering molecule on activated, but not fresh natural killer (NK) cells. In the current study, metabolic pathways used in CD44-directed lysis (CD44DL) were examined using activated human NK cells as effectors. We found that CD44 expressed by activated NK cells was indistinguishable in isoform and molecular weight from CD44 on unactivated cells. However, de novo protein expression was required for the induction of CD44DL, suggesting that activated NK cells contain proteins not present in fresh NK cells that couple CD44 to the lytic machinery. Concanimycin A, a selective inhibitor of perforin-based cytolysis, totally blocked CD44DL, natural cytototoxicity, and antibody-dependent cell-mediated cytolysis (ADCC). Moreover, studies in which kinase inhibitors were added during the effector phase of lysis indicated that protein-tyrosine and ser/thr kinases were required for all three cytolytic activities and that protein kinase C played a nonessential role in lysis. By contrast, wortmannin totally inhibited CD44DL, but failed to block natural cytotoxicity and only partially blocked ADCC, suggesting that phosphatidylinositol 3-kinase (PI 3-kinase) is required at an early, receptor-specific stage of CD44DL. Finally, cytochalasin B enhanced CD44DL, but not ADCC, indicating that CD44DL is modulated by actin polymerization. Taken together, our data suggest that CD44 in NK cells interacts with proteins induced during interleukin-2 activation in a triggering pathway that induces perforin release, requires PI 3-kinase, and is modulated by the cytoskeleton.
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15
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Abstract
AbstractCD44 is a cytotoxic triggering molecule on activated, but not fresh natural killer (NK) cells. In the current study, metabolic pathways used in CD44-directed lysis (CD44DL) were examined using activated human NK cells as effectors. We found that CD44 expressed by activated NK cells was indistinguishable in isoform and molecular weight from CD44 on unactivated cells. However, de novo protein expression was required for the induction of CD44DL, suggesting that activated NK cells contain proteins not present in fresh NK cells that couple CD44 to the lytic machinery. Concanimycin A, a selective inhibitor of perforin-based cytolysis, totally blocked CD44DL, natural cytototoxicity, and antibody-dependent cell-mediated cytolysis (ADCC). Moreover, studies in which kinase inhibitors were added during the effector phase of lysis indicated that protein-tyrosine and ser/thr kinases were required for all three cytolytic activities and that protein kinase C played a nonessential role in lysis. By contrast, wortmannin totally inhibited CD44DL, but failed to block natural cytotoxicity and only partially blocked ADCC, suggesting that phosphatidylinositol 3-kinase (PI 3-kinase) is required at an early, receptor-specific stage of CD44DL. Finally, cytochalasin B enhanced CD44DL, but not ADCC, indicating that CD44DL is modulated by actin polymerization. Taken together, our data suggest that CD44 in NK cells interacts with proteins induced during interleukin-2 activation in a triggering pathway that induces perforin release, requires PI 3-kinase, and is modulated by the cytoskeleton.
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