1,273 research outputs found
Assessment of fluorescent amplified fragment length polymorphism analysis for epidemiological genotyping of Legionella pneumophila serogroup 1
No full textIdentification of variable-number tandem-repeat (VNTR) sequences in Legionella pneumophila and development of an optimized multiple-locus VNTR analysis typing scheme
No full textThe utility of a genotypic typing assay for Legionella pneumophila was investigated. A multiple-locus variable number of tandem repeats (VNTR) analysis (MLVA) scheme using PCR and agarose gel electrophoresis is proposed based on eight minisatellite markers. Panels of well-characterized strains were examined in a multicenter analysis to validate the assay and to compare its performance to that of other genotyping assays. Excellent typeability, reproducibility, stability, and epidemiological concordance were observed. The MLVA type or profile is composed of a string of allelle numbers, corresponding to the number of repeats at each VNTR locus, separated by commas, in a predetermined order. A database containing information from 99 L. pneumophila serogroup I strains and four strains of other serogroups and their MLVA profiles, which can be queried online, is available from http://bacterial-genotyping.igmors.u-psud.fr/
Investigation of the population structure of Legionella pneumophila by analysis of tandem repeat copy number and internal sequence variation
No full textThe population structure of the species Legionella pneumophila was investigated by multilocus variable number of tandem repeats (VNTR) analysis (MLVA) and sequencing of three VNTRs (Lpms01, Lpms04 and Lpms13) in selected strains. Of 150 isolates of diverse origins, 136 (86%) were distributed into eight large MLVA clonal complexes (VACCs) and the rest were either unique or formed small clusters of up to two MLVA genotypes. In spite of the lower degree of genome-wide linkage disequilibrium of the MLVA loci compared with sequence-based typing, the clustering achieved by the two methods was highly congruent. The detailed analysis of VNTR Lpms04 alleles showed a very complex organization, with five different repeat unit lengths and a high level of internal variation. Within each MLVA-defined VACC, Lpms04 was endowed with a common recognizable pattern with some interesting exceptions. Evidence of recombination events was suggested by analysis of internal repeat variations at the two additional VNTR loci, Lpms01 and Lpms13. Sequence analysis of L. pneumophila VNTR locus Lpms04 alone provides a first-line assay for allocation of a new isolate within the L. pneumophila population structure and for epidemiological studies
Development of antibody technology to identify natural killer cell surface antigens in Xenopus Laevis
No full textNatural killer (NK)-like lymphocytes have recently been identified in thymectomised (Tx) Xenopus which are capable of spontaneous cytotoxicity towards the MHC- deficient, allogeneic thymus tumour cell line B(_3)B(_7). This Thesis describes attempts to raise antibodies to Xenopus NK cell surface antigens by phage display and hybridoma technology. The phage display technique was optimised for raising antibodies to novel, cellular antigens in a trial run using the Xenopus thymus tumour cell line B(_3)B(_7). Having isolated a phage antibody which was shown by flow cytometry to bind B(_3)B(_7) cells, the technique was then used to try and raise antibodies to Xenopus NK cells. Isolation of an NIC-specific phage antibody was not achieved but phage antibody XL-6 was raised, which bound an antigen on Xenopus lymphocytes. Phage antibody XL-6, and soluble scFv derived from this, were able to identify a putative mature T cell population in the thymus and may be specific for an amphibian homologue of the mammalian leukocyte common antigen CD45. Hybridoma technology was used to isolate three monoclonal antibodies, 1F8, 4D4 and 1G5, which were shown by flow cytometric analysis to identify a putative NK cell population in control and Tx Xenopus. Following immunomagnetic purification, 1F8- positive spleen cells from control and Tx animals were shown to kill the MHC- deficient tumour target B(_3)B(_7), confirming that this antibody was specific for Xenopus NK cells. Western blotting experiments showed that 1F8, 4D4 and 1G5 identified a doublet of protein bands at 72 and 74 kilodaltons in Xenopus gut lymphoid lysates. Initial attempts to isolate cDNA encoding a Xenopus NK cell surface antigen through immunoscreening a xenopus gut cDNA expression library with antibody 1G5 were unsuccessful as was an attempt to clone a Xenopus homologue of the mammalian NK receptor NKR-Pl by PGR
Clarence River, New South Wales, ca. 1848, 1 [picture] /
No full textAlso known as Thompson.; In: Views in New South Wales, Australia, ca. 1848.; Inscription: "Clarence River" --In ink below image.; Rex Nan Kivell Collection NK 671/6.; Title from inscription below image.; With: Commissioner Fry, Clarence River.; Also available in an electronic version via the Internet at: http://nla.gov.au/nla.pic-an4647862
The Adhesion G Protein-Coupled Receptor GPR56/ADGRG1 Is an Inhibitory Receptor on Human NK Cells
No full textSummaryNatural killer (NK) cells possess potent cytotoxic mechanisms that need to be tightly controlled. Here, we explored the regulation and function of GPR56/ADGRG1, an adhesion G protein-coupled receptor implicated in developmental processes and expressed distinctively in mature NK cells. Expression of GPR56 was triggered by Hobit (a homolog of Blimp-1 in T cells) and declined upon cell activation. Through studying NK cells from polymicrogyria patients with disease-causing mutations in ADGRG1, encoding GPR56, and NK-92 cells ectopically expressing the receptor, we found that GPR56 negatively regulates immediate effector functions, including production of inflammatory cytokines and cytolytic proteins, degranulation, and target cell killing. GPR56 pursues this activity by associating with the tetraspanin CD81. We conclude that GPR56 inhibits natural cytotoxicity of human NK cells
[Portion of America] [cartographic material].
No full textSection of a map of America with relief shown pictorially.; Title and author information taken from pencil notes on verso of map.; Rex Nan Kivell Collection Map NK 10432
In Vivo IFN-γ Secretion by NK Cells in Response to Salmonella Typhimurium Requires NLRC4 Inflammasomes
No full textabstract: Natural killer (NK) cells are a critical part of the innate immune defense against viral infections and for the control of tumors. Much less is known about how NK cells contribute to anti-bacterial immunity. NK cell-produced interferon gamma (IFN-γ) contributes to the control of early exponential replication of bacterial pathogens, however the regulation of these events remains poorly resolved. Using a mouse model of invasive Salmonellosis, here we report that the activation of the intracellular danger sensor NLRC4 by Salmonella-derived flagellin within CD11c[superscript +] cells regulates early IFN-γ secretion by NK cells through the provision of interleukin 18 (IL-18), independently of Toll-like receptor (TLR)-signaling. Although IL18-signalling deficient NK cells improved host protection during S. Typhimurium infection, this increased resistance was inferior to that provided by wild-type NK cells. These findings suggest that although NLRC4 inflammasome-driven secretion of IL18 serves as a potent activator of NK cell mediated IFN-γ secretion, IL18-independent NK cell-mediated mechanisms of IFN-γ secretion contribute to in vivo control of Salmonella replication.The article is published at http://journals.plos.org/plosone/article?id=10.1371/journal.pone.009741
HCMV vCXCL1 Binds Several Chemokine Receptors and Preferentially Attracts Neutrophils over NK Cells by Interacting with CXCR2
No full textSummaryHCMV is a highly sophisticated virus that has developed various mechanisms for immune evasion and viral dissemination throughout the body (partially mediated by neutrophils). NK cells play an important role in elimination of HCMV-infected cells. Both neutrophils and NK cells utilize similar sets of chemokine receptors to traffic, to and from, various organs. However, the mechanisms by which HCMV attracts neutrophils and not NK cells are largely unknown. Here, we show a unique viral protein, vCXCL1, which targets three chemokine receptors: CXCR1 and CXCR2 expressed on neutrophils and CXCR1 and CX3CR1 expressed on NK cells. Although vCXCL1 attracted both cell types, neutrophils migrated faster and more efficiently than NK cells through the binding of CXCR2. Therefore, we propose that HCMV has developed vCXCL1 to orchestrate its rapid systemic dissemination through preferential attraction of neutrophils and uses alternative mechanisms to counteract the later attraction of NK cells
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