51
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Contemporary diagnostic methods for hemophagocytic lymphohistiocytic disorders. J Immunol Methods 2010; 364:1-13. [PMID: 21110979 DOI: 10.1016/j.jim.2010.11.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2010] [Revised: 10/10/2010] [Accepted: 11/16/2010] [Indexed: 12/26/2022]
Abstract
Hemophagocytic lymphohistiocytosis is a life-threatening multi-system hyperinflammatory disorder characterized by dysfunctional cytolytic lymphocyte responses, hypercytokinemia, and widespread lymphohistiocytic tissue infiltration and destruction. Diagnosis and definitive therapy are often delayed as clinical efforts are directed toward treatment of presumed overwhelming infection. Sporadic cases occur in association with underlying immune dysfunction related to autoimmune disease, malignancy, or severe infection. However, familial cases predominate with remarkable associations between underlying genetic defects and dysregulation of immune responses. Here, we review the genetic and immunologic basis of contemporary diagnostic methods for hemophagocytic lymphohistiocytosis.
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Watzl C, Long EO. Signal transduction during activation and inhibition of natural killer cells. CURRENT PROTOCOLS IN IMMUNOLOGY 2010; Chapter 11:Unit 11.9B. [PMID: 20814939 PMCID: PMC3857016 DOI: 10.1002/0471142735.im1109bs90] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Natural killer (NK) cells are important for early immune responses to viral infections and cancer. Upon activation, NK cells secrete cytokines and chemokines, and kill sensitive target cells by releasing the content of cytolytic granules. This unit is focused on the signal transduction pathways that regulate NK cell activities in response to contact with other cells. We will highlight signals regulating NK cell adhesion to target cells and describe the induction of cellular cytotoxicity by the engagement of different NK cell activation receptors. Negative signaling induced by inhibitory receptors opposes NK cell activation and provides an important safeguard from NK cell reactivity toward normal, healthy cells. We will discuss the complex integration of the different signals that occur during interaction of NK cells with target cells.
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Affiliation(s)
- Carsten Watzl
- Institute for Immunology, University Heidelberg, Heidelberg, Germany
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53
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Pachlopnik Schmid J, Schmid JP, Côte M, Ménager MM, Burgess A, Nehme N, Ménasché G, Fischer A, de Saint Basile G. Inherited defects in lymphocyte cytotoxic activity. Immunol Rev 2010; 235:10-23. [PMID: 20536552 DOI: 10.1111/j.0105-2896.2010.00890.x] [Citation(s) in RCA: 130] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The granule-dependent cytotoxic activity of lymphocytes plays a critical role in the defense against virally infected cells and tumor cells. The importance of this cytotoxic pathway in immune regulation is evidenced by the severe and often fatal condition, known as hemophagocytic lymphohistiocytic syndrome (HLH) that occurs in mice and humans with genetically determined impaired lymphocyte cytotoxic function. HLH manifests as the occurrence of uncontrolled activation of T lymphocytes and macrophages infiltrating multiple organs. In this review, we focus on recent advances in the characterization of effectors regulating the release of cytotoxic granules, and on the role of this cytotoxic pathway in lymphocyte homeostasis and immune surveillance. Analysis of the mechanisms leading to the occurrence of hemophagocytic syndrome designates gamma-interferon as an attractive therapeutic target to downregulate uncontrolled macrophage activation, which sustains clinical and biological features of HLH.
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Affiliation(s)
- Jana Pachlopnik Schmid
- Institut National de la Santé et de la Recherche Médicale (INSERM), U768, 75015 Paris, France
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54
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Mutations of perforin gene in Chinese patients with acute lymphoblastic leukemia. Leuk Res 2010; 35:196-9. [PMID: 20638125 DOI: 10.1016/j.leukres.2010.06.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2010] [Revised: 06/10/2010] [Accepted: 06/16/2010] [Indexed: 11/22/2022]
Abstract
To address whether mutations and single nucleotide polymorphisms (SNPs) in perforin gene (PRF1) are correlated with acute lymphoblastic leukemia (ALL) in Chinese, we screened mutations in codon region of PRF1 in 111 ALL patients, and correlated the results with patients' immunophenotype, karyotype and fusion genes. Four novel monoallelic missense and two novel monoallelic synonymous mutations (G198R, R225Q, D486G, R509K, S388S and Q540Q) were identified in 9 B-ALL, of whom 7 cases carried BCR-ABL gene, one carried MLL-AF4 fusion gene, and one lost two chromosomes. Our results suggest that mutations in PRF1 may play a role in the pathogenesis of B-ALL.
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Marsh RA, Satake N, Biroschak J, Jacobs T, Johnson J, Jordan MB, Bleesing JJ, Filipovich AH, Zhang K. STX11 mutations and clinical phenotypes of familial hemophagocytic lymphohistiocytosis in North America. Pediatr Blood Cancer 2010; 55:134-40. [PMID: 20486178 DOI: 10.1002/pbc.22499] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND Mutations in STX11 are responsible for Familial Hemophagocytic Lymphohistiocytosis (FHLH) type 4, a rare primary immunodeficiency which has previously been observed only in patients of Kurdish, Turkish, and Lebanese ethnic background. METHODS We reviewed our experience with STX11 mutations among North American patients and studied the impact of patient mutations upon syntaxin 11 expression and NK cell function. RESULTS Between 2007 and 2008, 243 patients with HLH (lacking disease-causing mutations in PRF1 and UNC13D) were referred for STX11 mutational analysis. We observed 1 novel homozygous nonsense mutation, 73 G > T (E25X), occurring in Hispanic siblings, and 2 novel biallelic heterozygous missense mutations, 106G > C (E36Q) and 616G > A (E206K), occurring in 1 Caucasian patient. The N-terminal nonsense mutation resulted in absence of detectable syntaxin 11 and abrogation of in vitro NK cell degranulation and function, while the biallelic heterozygous missense mutations resulted in detectable mutated syntaxin 11 and preservation of in vitro NK cell degranulation and cytotoxicity. The two sibling patients with the nonsense mutations presented with HLH during infancy, whereas the patient with biallelic heterozygous missense mutations presented at 5 years of age. CONCLUSION We conclude that mutations in STX11 are responsible for HLH in approximately 1% of North American patients and can cause variable defects in syntaxin 11 expression and function with resultant impact on clinical phenotype.
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Affiliation(s)
- Rebecca A Marsh
- Division of Bone Marrow Transplant and Immune Deficiency, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229, USA.
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56
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Dressel R, Elsner L, Novota P, Kanwar N, Fischer von Mollard G. The exocytosis of lytic granules is impaired in Vti1b- or Vamp8-deficient CTL leading to a reduced cytotoxic activity following antigen-specific activation. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2010; 185:1005-14. [PMID: 20543108 DOI: 10.4049/jimmunol.1000770] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2023]
Abstract
The exocytosis of cytotoxic proteins stored in lytic granules of activated CTL is a key event during killing of target cells. Membrane fusion events that are mediated by soluble N-ethylmaleimide-sensitive-factor attachment protein receptor (SNARE) proteins are crucial, as demonstrated by patients with familial hemophagocytic lymphohistocytosis type 4 who have mutations in the SNARE protein syntaxin-11 that result in an impaired degranulation of cytotoxic cells. We found an increased mRNA expression of the SNARE protein genes Vti1b and Vamp8 during Ag-specific activation of CTL from TCR-transgenic OT-I mice. Therefore, we investigated the cytolytic activity of CTL from TCR-transgenic Vti1b and Vamp8 knockout mice. At 3 d as well as at 4 d of Ag-specific stimulation, the degranulation of CTL was significantly reduced in Vti1b and Vamp8 knockout mice, as determined by cell surface expression of the degranulation marker CD107a. After 3 d of Ag-specific stimulation, the cytolytic activity of Vti1b- and Vamp8-deficient CTL was reduced to approximately 50% compared with heterozygous controls. However, 4 d after stimulation, the cytotoxic activity of Vti1b- as well as Vamp8-deficient CTL was not impaired anymore. The capacity of Vti1b- and Vamp8-deficient dendritic cells to process Ags and to stimulate the proliferation of CTL was not reduced, arguing against an indirect effect on the activation of CTL. These findings suggest a role of the SNARE proteins vti1b and vesicle-associated membrane protein 8 in the degranulation of CTL. However, a deficiency can apparently be compensated and affects only transiently the cytotoxic activity of CTL during their development to armed effector cells.
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Affiliation(s)
- Ralf Dressel
- Department of Cellular and Molecular Immunology, University Medical Center, University of Göttingen, Göttingen, Germany.
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57
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Sanborn KB, Orange JS. Navigating barriers: the challenge of directed secretion at the natural killer cell lytic immunological synapse. J Clin Immunol 2010; 30:358-63. [PMID: 20191315 PMCID: PMC2874632 DOI: 10.1007/s10875-010-9372-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2010] [Accepted: 01/17/2010] [Indexed: 01/12/2023]
Abstract
INTRODUCTION Natural killer (NK) cells have an inherent ability to recognize and destroy a wide array of cells rendered abnormal by stress or disease. NK cells can kill a targeted cell by forming a tight interface-the lytic immunological synapse. This represents a dynamic molecular arrangement that over time progresses through a series of steps to ultimately deliver the contents of specialized organelles known as lytic granules. DISCUSSION In order to mediate cytotoxicity, the NK cell faces the challenge of mobilizing the lytic granules, polarizing them to the targeted cell, facilitating their approximation to the NK cell membrane, and releasing their contents. CONCLUSION This review is focused upon the final steps in accessing function through the lytic immunological synapse.
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Affiliation(s)
- Keri B. Sanborn
- Immunology Graduate Group, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
| | - Jordan S. Orange
- Immunology Graduate Group, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA; Children's Hospital Research Institute, Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA; Abramson Research Center 1014H, Division of Immunology, Children's Hospital of Philadelphia, 3615 Civic Center Boulevard, Philadelphia, PA 19104, USA
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58
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Danielian S, Basile N, Rocco C, Prieto E, Rossi J, Barsotti D, Roche PA, Bernasconi A, Oleastro M, Zelazko M, Braier J. Novel syntaxin 11 gene (STX11) mutation in three Argentinean patients with hemophagocytic lymphohistiocytosis. J Clin Immunol 2009; 30:330-7. [PMID: 19967551 DOI: 10.1007/s10875-009-9350-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Accepted: 11/11/2009] [Indexed: 10/20/2022]
Abstract
INTRODUCTION Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening disease with major diagnostic and therapeutic difficulties, basically comprising two different conditions: primary and secondary forms. Recent advances regarding molecular diagnosis may be useful to distinguish from one another, especially in sporadic cases starting in early infancy. MATERIALS AND METHODS In this report, we evaluated three Argentinean patients with clinical suspicion of HLH, but without family history. We excluded mutations in the perforin gene but identified in the three patients a novel homozygous deletion (c. 581_584delTGCC; p.Leu194ProfsX2) in the gene-encoding syntaxin 11 (STX11), causing a premature termination codon. RESULTS AND CONCLUSION Each parent from the three unrelated families resulted heterozygous for this deletion confirming the diagnosis of familial hemophagocytic lymphohistiocytosis type 4. Patients shared the same single-nucleotide polymorphism profile in STX11 gene, and genotyping at ten microsatellites surrounding this gene support the presence of a single-haplotype block carrying the novel mutation.
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Affiliation(s)
- Silvia Danielian
- Servicio de Inmunologia y Reumatologia, Hospital de Pediatria Juan P Garrahan, Buenos Aires, Argentina.
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59
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Abstract
Natural killer (NK) cells target and kill aberrant cells, such as virally infected and tumorigenic cells. Killing is mediated by cytotoxic molecules which are stored within secretory lysosomes, a specialized exocytic organelle found in NK cells. Target cell recognition induces the formation of a lytic immunological synapse between the NK cell and its target. The polarized exocytosis of secretory lysosomes is then activated and these organelles release their cytotoxic contents at the lytic synapse, specifically killing the target cell. The essential role that secretory lysosome exocytosis plays in the cytotoxic function of NK cells is highlighted by immune disorders that are caused by the mutation of critical components of the exocytic machinery. This review will discuss recent studies on the molecular basis for NK cell secretory lysosome exocytosis and the immunological consequences of defects in the exocytic machinery.
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Affiliation(s)
- Nicola J Topham
- Faculty of Biological Sciences, Institute of Molecular and Cellular Biology, University of Leeds, Leeds, UK
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60
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Pores-Fernando AT, Zweifach A. Calcium influx and signaling in cytotoxic T-lymphocyte lytic granule exocytosis. Immunol Rev 2009; 231:160-73. [PMID: 19754896 DOI: 10.1111/j.1600-065x.2009.00809.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Cytotoxic T lymphocytes (CTLs) kill targets by releasing cytotoxic agents from lytic granules. Killing is a multi-step process. The CTL adheres to a target, allowing its T-cell receptors to recognize antigen. This triggers a signal transduction cascade that leads to the polarization of the microtubule cytoskeleton and granules towards the target, followed by exocytosis that occurs specifically at the site of contact. As with cytokine production by helper T cells (Th cells), target cell killing is absolutely dependent on Ca2+ influx, which is involved in regulating both reorientation and release. Current evidence suggests that Ca2+ influx in CTLs, as in Th cells, occurs via depletion-activated channels. The molecules that couple increases in Ca2+ to reorientation are unknown. The Ca2+/calmodulin-dependent phosphatase calcineurin, which plays a critical role in cytokine production by Th cells, is also involved in lytic granule exocytosis, although the relevant substrates remain to be identified and calcineurin activation is only one Ca2+-dependent step involved. There are thus striking similarities and important differences between Ca2+ signals in Th cells and CTLs, illustrating how cells can use similar signal transduction pathways to generate different functional outcomes.
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Affiliation(s)
- Arun T Pores-Fernando
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT, USA
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61
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Familial hemophagocytic lymphohistiocytosis type 5 (FHL-5) is caused by mutations in Munc18-2 and impaired binding to syntaxin 11. Am J Hum Genet 2009; 85:482-92. [PMID: 19804848 DOI: 10.1016/j.ajhg.2009.09.005] [Citation(s) in RCA: 282] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2009] [Revised: 09/03/2009] [Accepted: 09/04/2009] [Indexed: 12/12/2022] Open
Abstract
Rapid intracellular transport and secretion of cytotoxic granules through the immunological synapse requires a balanced interaction of several proteins. Disturbance of this highly regulated process underlies familial hemophagocytic lymphohistiocytosis (FHL), a genetically heterogeneous autosomal-recessive disorder characterized by a severe hyperinflammatory phenotype. Here, we have assigned FHL-5 to a 1 Mb region on chromosome 19p by using high-resolution SNP genotyping in eight unrelated FHL patients from consanguineous families. Subsequently, we found nine different mutations, either truncating or missense, in STXBP2 in twelve patients from Turkey, Saudi Arabia, and Central Europe. STXBP2 encodes syntaxin binding protein 2 (Munc18-2), involved in the regulation of vesicle transport to the plasma membrane. We have identified syntaxin 11, a SNARE protein mutated in FHL-4, as an interaction partner of STXBP2. This interaction is eliminated by the missense mutations found in our FHL-5 patients, which leads to a decreased stability of both proteins, as shown in patient lymphocytes. Activity of natural killer and cytotoxic T cells was markedly reduced or absent, as determined by CD107 degranulation. Our findings thus identify a key role for STXBP2 in lytic granule exocytosis.
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62
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Angeborene Störungen der Immunregulation. Monatsschr Kinderheilkd 2009. [DOI: 10.1007/s00112-009-1988-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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63
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Xie LX, de la Iglesia-Vicente J, Fang YX, Mollinedo F. Expression and subcellular localization of syntaxin 11 in human neutrophils. Inflamm Res 2009; 58:407-12. [DOI: 10.1007/s00011-009-0006-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2008] [Revised: 11/23/2008] [Accepted: 12/09/2008] [Indexed: 11/29/2022] Open
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64
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Filipovich AH. Hemophagocytic lymphohistiocytosis (HLH) and related disorders. HEMATOLOGY. AMERICAN SOCIETY OF HEMATOLOGY. EDUCATION PROGRAM 2009; 2009:127-131. [PMID: 20008190 DOI: 10.1182/asheducation-2009.1.127] [Citation(s) in RCA: 234] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Hemophagocytic lymphohistiocytosis (HLH), which has many genetic causes, is characterized by multi-system inflammation. HLH is a reactive process resulting from prolonged and excessive activation of antigen presenting cells (macrophages, histiocytes) and CD8(+) T cells. Hemophagocytosis, which is mediated through the CD163 heme-scavenging receptor, is a hallmark of activated macrophages/histiocytes and is the characteristic finding for which the disorder was named. The majority of genetic causes identified to date affect the cytotoxic function of NK and T cells, crippling immunologic mechanisms that mediate natural immune contraction. The predominant clinical findings of HLH are fevers (often hectic and persistent), cytopenias, hepatitis and splenomegaly. Due to the life-threatening implications of the diagnosis of genetically determined HLH, antiinflammatory therapy, often consisting of steroids, etoposide or antithymocyte globulin (ATG), should be instituted promptly, followed by curative hematopoietic cell transplantation. Secondary HLH, associated with autoimmune disorders or viral infections in teens and adults, also carries a significant mortality rate and should be managed in consultation with specialists familiar with the diagnosis and treatment of such disorders.
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MESH Headings
- Adolescent
- Adult
- Age of Onset
- Aged
- Anti-Inflammatory Agents/therapeutic use
- Antigen Presentation
- Autoimmune Diseases/drug therapy
- Autoimmune Diseases/etiology
- Autoimmune Diseases/surgery
- Child
- Child, Preschool
- Female
- Hematopoietic Stem Cell Transplantation
- Histiocytes/immunology
- Humans
- Immunosuppressive Agents/therapeutic use
- Infant
- Infant, Newborn
- Inflammation/immunology
- Killer Cells, Natural/immunology
- Lymphocyte Activation
- Lymphohistiocytosis, Hemophagocytic/diagnosis
- Lymphohistiocytosis, Hemophagocytic/drug therapy
- Lymphohistiocytosis, Hemophagocytic/epidemiology
- Lymphohistiocytosis, Hemophagocytic/etiology
- Lymphohistiocytosis, Hemophagocytic/genetics
- Lymphohistiocytosis, Hemophagocytic/surgery
- Lymphoproliferative Disorders/complications
- Lymphoproliferative Disorders/genetics
- Male
- Middle Aged
- Mutation
- T-Lymphocyte Subsets/immunology
- Transplantation, Homologous
- Virus Diseases/complications
- Young Adult
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Affiliation(s)
- Alexandra H Filipovich
- Division of Hematology/Oncology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229-3039, USA.
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65
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Ma JSY, Haydar TF, Radoja S. Protein kinase C delta localizes to secretory lysosomes in CD8+ CTL and directly mediates TCR signals leading to granule exocytosis-mediated cytotoxicity. THE JOURNAL OF IMMUNOLOGY 2008; 181:4716-22. [PMID: 18802074 DOI: 10.4049/jimmunol.181.7.4716] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Lytic granule exocytosis is the major effector function used by CD8(+) CTL in response to intracellular pathogens and tumors. Despite recent progress in the field, two important aspects of this cytotoxic mechanism remain poorly understood. First, TCR-signaling pathway(s) that selectively induces granule exocytosis in CTL has not been defined to date. Second, it is unclear how Ag receptor-induced signals are converted into mobilization of lytic granules. We recently demonstrated that protein kinase C delta (PKC delta) selectively regulates TCR-induced lytic granule polarization in mouse CD8(+) CTL. To better understand how PKC delta facilitates granule movement, here we studied dynamics of intracellular localization of PKC delta in living CD8(+) CTL. Strikingly, we found that PKC delta localizes to the secretory lysosomes and polarizes toward immunological synapse during the process of target cell killing. Also, biochemical and structure-function studies demonstrated that upon TCR ligation, PKC delta becomes rapidly phosphorylated on the activation loop and regulates granule exocytosis in a kinase-dependent manner. Altogether, our current studies provide new insights concerning the regulation of TCR-induced lytic granule exocytosis by revealing novel intracellular localization of PKC delta, providing the first example of colocalization of a kinase with secretory lysosomes in CD8(+) CTL and demonstrating that PKC delta directly transduces TCR signals leading to polarized granule secretion.
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Affiliation(s)
- Jennifer S Y Ma
- Center for Cancer and Immunology, Children's National Medical Center, Children's Research Institute, Washington, DC 20010, USA
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66
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Arneson LN, Segovis CM, Gomez TS, Schoon RA, Dick CJ, Lou Z, Billadeau DD, Leibson PJ. Dynamin 2 regulates granule exocytosis during NK cell-mediated cytotoxicity. THE JOURNAL OF IMMUNOLOGY 2008; 181:6995-7001. [PMID: 18981119 DOI: 10.4049/jimmunol.181.10.6995] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
NK cells are innate immune cells that can eliminate their targets through granule release. In this study, we describe a specialized role for the large GTPase Dynamin 2 (Dyn2) in the regulation of these secretory events leading to cell-mediated cytotoxicity. By modulating the expression of Dyn2 using small interfering RNA or by inhibiting its activity using a pharmacological agent, we determined that Dyn2 does not regulate conjugate formation, proximal signaling, or granule polarization. In contrast, during cell-mediated killing, Dyn2 localizes with lytic granules and polarizes to the NK cell-target interface where it regulates the final fusion of lytic granules with the plasma membrane. These findings identify a novel role for Dyn2 in the exocytic events required for effective NK cell-mediated cytotoxicity.
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Affiliation(s)
- Laura N Arneson
- Department of Immunology, College of Medicine, Mayo Clinic, Rochester, MN 55905, USA
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67
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Abstract
The natural killer (NK)-cell immunological synapse is the dynamic interface formed between an NK cell and its target cell. Formation of the NK-cell immunological synapse involves several distinct stages, from the initiation of contact with a target cell to the directed delivery of lytic-granule contents for target-cell lysis. Progression through the individual stages is regulated, and this tight regulation underlies the precision with which NK cells select and kill susceptible target cells (including virally infected cells and cancerous cells) that they encounter during their routine surveillance of the body.
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Affiliation(s)
- Jordan S Orange
- University of Pennsylvania School of Medicine, Joseph Stokes Jr Research Institute of The Children's Hospital of Philadelphia, 3615 Civic Center Boulevard, ARC 1016H, Philadelphia, Pennsylvania 19104, USA.
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68
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Filipovich AH. Hemophagocytic lymphohistiocytosis and other hemophagocytic disorders. Immunol Allergy Clin North Am 2008; 28:293-313, viii. [PMID: 18424334 DOI: 10.1016/j.iac.2008.01.010] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Hemophagocytic disorders result when critical regulatory pathways responsible for the natural termination of immune/inflammatory responses are disrupted or overwhelmed. Hemophagocytic disorders reflect pathologic defects that alter the normal crosstalk between innate and adaptive immune responses, and compromise homeostatic removal of cells that are superfluous or dangerous to the organism. Although hemophagocytic disorders are considered rare, increased awareness of these conditions has led to more frequent diagnoses, more rapid initiation of life-saving treatments, and new insights into the molecules and pathways involved in natural immune down-regulation. Furthermore, improved understanding of the immunologic abnormalities revealed by hemophagocytic disorders informs potential new treatments for life-threatening multisystem organ dysfunction related to sepsis in the intensive care unit setting and severe cases.
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Affiliation(s)
- Alexandra H Filipovich
- Division of Hematology/Oncology, Immunodeficiency and Histiocytosis Program, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229-3039, USA.
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69
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Zhang S, Ma D, Wang X, Celkan T, Nordenskjld M, Henter JI, Fadeel B, Zheng C. Syntaxin-11 is expressed in primary human monocytesmacrophages and acts as a negative regulator of macrophage engulfment of apoptotic cells and IgG-opsonized target cells. Br J Haematol 2008; 142:469-79. [DOI: 10.1111/j.1365-2141.2008.07191.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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70
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Krzewski K, Strominger JL. The killer's kiss: the many functions of NK cell immunological synapses. Curr Opin Cell Biol 2008; 20:597-605. [PMID: 18639449 DOI: 10.1016/j.ceb.2008.05.006] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2008] [Revised: 05/15/2008] [Accepted: 05/19/2008] [Indexed: 01/18/2023]
Abstract
Natural killer (NK) cells comprise a subset of lymphocytes involved in protection against microbial pathogens and tumors. NK cells recognize host cells that are missing MHC class I molecules and eliminate them through localized delivery of lytic granules. The majority of NK cell effector functions require direct cell-to-cell contact. Binding to a target cell is accompanied by creation of complex structures at the cell-cell interface known as immunological synapses. Recent studies have contributed immensely to the characterization of several types of NK cell immunological synapses and understanding of the variety of processes originating at this intriguing place. The emerging picture illustrates NK cell immune synapses as the sites of highly complex regulation of NK cell activity.
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Affiliation(s)
- Konrad Krzewski
- Department of Molecular and Cellular Biology, Harvard University, 7 Divinity Avenue, Cambridge, MA 02138, USA
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71
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Bryceson YT, Long EO. Line of attack: NK cell specificity and integration of signals. Curr Opin Immunol 2008; 20:344-52. [PMID: 18439809 DOI: 10.1016/j.coi.2008.03.005] [Citation(s) in RCA: 164] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2008] [Revised: 03/09/2008] [Accepted: 03/10/2008] [Indexed: 12/13/2022]
Abstract
Natural killer (NK) cells possess potent cytolytic activity and secrete immune modulating cytokines. The large repertoire of NK cell receptors provides versatility for the identification of infected and transformed cells and for their elimination by NK cells. NK cell responses also stimulate and regulate the adaptive arm of the immune system. We review current knowledge about the molecular specificity of NK cell receptors and about the regulation of NK cell effector functions upon encounter with target cells. Mechanisms of recognition, interplay among receptors, signal integration, and the dynamic fine-tuning of NK cell responses are discussed. New insights into the molecular checkpoints for NK cell effector function are highlighted, and underlying reasons for the complexity in NK cell recognition and signaling are proposed.
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Affiliation(s)
- Yenan T Bryceson
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA.
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72
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Higashio H, Nishimura N, Ishizaki H, Miyoshi J, Orita S, Sakane A, Sasaki T. Doc2α and Munc13-4 Regulate Ca2+-Dependent Secretory Lysosome Exocytosis in Mast Cells. THE JOURNAL OF IMMUNOLOGY 2008; 180:4774-84. [DOI: 10.4049/jimmunol.180.7.4774] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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