1,720,963 research outputs found
Natural killer cells: integrating diversity with function
No full textThe key role of natural killer cells in many aspects of the immune response is now being recognized. The last decade has seen an exponential increase in our understanding of the workings of these cells. Receptor diversity is crucial in allowing natural killer cells to respond effectively to a variety of different pathogens. This article reviews aspects of natural killer cell diversity that combine to generate populations of functional natural killer cells that exist within both the individual and throughout the population at large
Natural killer cells and hepatitis C: action and reaction
No full textIn 1989, hepatitis C virus (HCV) was first identified as the infectious agent responsible for human non-A, non-B hepatitis. Two decades later, HCV remains a global public health problem with a suboptimal response rate to treatment and the absence of a protective vaccine. Recent work has highlighted the influence of the innate immune system, and in particular natural killer cells, on the outcome and pathology of HCV infection. These cells are considerably more complex than was originally thought and their role in viral infections is currently being unravelled. This review summarises our emerging understanding of natural killer cells in HCV infection
NK receptors: it's all in the name
No full textWe read with interest the paper by Muhanna et al on natural killer cells, their role in ameliorating liver fibrosis and in particular the role of inhibitory receptors for major histocompatibility complex (MHC) class I.1 We would like to clarify the often confusing terminology of inhibitory receptors for natural killer cells
A study of MHC class I binding viral and host derived peptides and natural killer cell function
Get PDFNatural killer (NK) cells are a key component of innate immunity and have been implicated in determining the outcome of HCV infection in both genetic and functional studies. The last two decades have seen significant advances in the understanding of NK cell regulation with the discovery of a multitude of activating and inhibitory receptors. CD94:NKG2A operates in tandem with the polymorphic killer cell immunoglobulin-like receptors (KIR) and Ly49 systems to inhibit NK cells, however it is not clear as to the benefits of having two distinct inhibitory receptor:ligand systems. Down regulation or modification of MHC class I expression is a key feature of NK cell recognition of virus infected cells. However, viruses can subvert this mechanism of NK cell surveillance by encoding peptides that can bind to MHC class I. The aim of this thesis is to further our understanding of the interaction between viral and host derived MHC class I binding peptides and their effect on NK cell inhibition.
By using an MHC deficient cell line, we have shown that HCV core35-44 peptide is capable of enhancing cell surface expression of MHC class I (HLA-C and HLA-E). Although this peptide stabilises HLA-E, the HLA-E:HCV core35-44 complex alone is insufficient to inhibit at NKG2A positive NK cells. However, in the presence of HLA-E binding MHC class I signal peptides, HCV core35-44 has a synergistic effect in suppressing the NKG2A+ NK cell population. Peptides derived from other viruses such as EBV and HIV, and the stress related peptide derived from heat shock protein 60 also augment inhibition of NKG2A+ NK cells, but only when in the presence of MHC class I signal peptides. This augmentation is caused by recruitment of the non-signalling CD94 molecule to the immune synapse in the absence of its inhibitory signalling partner NKG2A. Thus CD94 can function independently as an enhancer of inhibition.
The augmentation of inhibition of CD94:NKG2A by non-inhibitory peptides, contrasts with antagonism of inhibition of KIR by low affinity peptide:MHC complexes. We also show that KIR+ and NKG2A+ NK cells respond with differing stoichiometries to MHC class I down-regulation. Thus peptide selectivity and MHC class I sensitivity of natural killer cell receptors provides a rationale for the evolution of two distinct inhibitory systems for MHC class I.Open Acces
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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