1,720,975 research outputs found
Immunomodulatory effects of intravenous immunoglobulin - assembling a jigsaw puzzle
No full textIntravenous immunoglobulin (IVIG) is widely used for the treatment of autoimmune and inflammatory disorders because of its immunomodulatory effects. The interaction of IVIG with the immune system has been extensively investigated over the past 30 years but, since IVIG modifies responses of many immune cells, a unifying model is far from reach. Here we survey the in vitro studies on the effects on IVIG on macrophages, B cells, T regulatory cells, dendritic cells and soluble factors, as well as the in vivo studies in murine disease models and the preliminary in vivo findings in humans
Clonal expansion and functional exhaustion of monoclonal marginal zone B cells in mixed cryoglobulinemia: The yin and yang of HCV-driven lymphoproliferation and autoimmunity
No full textMonoclonal marginal zone (MZ) B cells expressing a VH1-69-encoded idiotype accumulate in HCV-associated mixed cryoglobulinemia (MC). These cells recognize the E2 protein of HCV and their massive clonal expansion reflects the propensity of MZ B cells to proliferate robustly upon antigenic stimulation by microorganisms, a property that makes them prone to neoplastic transformation. VH1-69+ B cells of MC patients are phenotypically heterogeneous and resemble either mature MZ B cells (IgM+CD27+CD21high) or the unusual CD21low B cells that accumulate in other immunological disorders such as common variable immunodeficiency (CVID) or HIV infection. The CD21low VH1-69+ B cells of MC patients, like those of CVID and HIV patients, are anergic to BCR and TLR9 stimulation and display deregulation of several anergy-related genes; proliferative anergy is also observed in CD21high MZ-like VH1-69+ B cells, that over-express the antiproliferative transcriptional repressor Stra13. Upon evolution to splenic marginal zone lymphoma, MZ-like VH1-69+ B cells down-regulate Stra13 and partially recover their capacity to proliferate in response to TLR9 ligation. Like yin and yang, robust clonal expansion and early proliferative anergy may be viewed as the opposite forces balancing the responses of human MZ B cells to chronic microbial stimuli. Disruption of this balance facilitates autoimmunity and lymphoproliferation. © 2012 Elsevier B.V
Intravenous immunoglobulin replacement therapy in common variable immunodeficiency induces B cell depletion through differentiation into apoptosis-prone CD21low B cells
No full textntravenous immunoglobulin (IVIG), besides its use as replacement therapy in patients with antibody defi- ciencies, is broadly used as an immunomodulatory agent for the treatment of autoimmune and inflammatory disorders. The mechanisms of action of IVIG include Fc receptor blockade, inhibition of cytokines and growth factors, modulation of macrophages and dendritic cells, enhancement of regulatory T cells, and modulation of B cells through the FccRIIB receptor and CD22. Recent studies suggest that in vitro exposure of human B cells to IVIG determines functional changes reminiscent of anergy and that IVIG treatment of patients with common variable immunodeficiency (CVID) induces in B cells ERK activation, a feature of anergy. Here, we show that IVIG therapy drives the B cells of patients with CVID to down-regulate CD21 expression and to assume the peculiar phenotype of the anergic-like, apoptosis-prone CD21low B cells that are spontaneously expanded in a subset of CVID and in some other immunological disorders. The CD21low B cells newly generated after IVIG infusion undergo spontaneous apoptosis upon in vitro culture. Furthermore, IVIG infusion is rapidly followed by a significant, although discrete, decrease in the number of circulating B cells, but not of T cells or of natural killer cells. These findings suggest that IVIG therapy may constrain antibody responses by inducing B cell depletion through differentiation into CD21low B cells that undergo accelerated apoptosis
Dysregulated extracellular signal-regulated kinase signaling associated with impaired B-cell receptor endocytosis in patients with common variable immunodeficiency
No full textBACKGROUND:
Common variable immunodeficiency (CVID) is a heterogeneous disorder characterized by B-cell dysfunction and, in a subgroup, by expansion of CD21(low) B cells. The CD21(low) B cells display defects in early B-cell receptor (BCR) signaling resembling those of anergic B cells.
OBJECTIVE:
We sought to investigate whether B cells from patients with CVID, like anergic B cells, have defects in extracellular signal-regulated kinase (ERK) phosphorylation and in endocytic trafficking of the BCR.
METHODS:
Using flow cytometry, we evaluated phosphorylated ERK (pERK) expression and internalization of cross-linked BCR in B-cell subsets. The localization of internalized BCR to lysosome-associated membrane protein 1-positive late endosomes was evaluated with confocal microscopy.
RESULTS:
Constitutive pERK levels were increased in naive and IgM(+) memory B cells of patients with CVID compared with those of healthy donors, whereas the pERK increment induced by BCR cross-linking was relatively reduced. Intravenous immunoglobulin administration enhanced these anomalies, but they appeared to be intrinsic to B cells from patients with CVID. Cross-linking-induced BCR endocytosis was decreased in the IgM(+) memory B cells, especially in those with a CD21(low) phenotype, but not in the naive B cells of patients with CVID with CD21(low) expansion. Internalized BCR localized normally to late endosomes. Pharmacologic inhibition of ERK phosphorylation suppressed BCR endocytosis in B cells of healthy patients and those with CVID.
CONCLUSIONS:
The B cells of patients with CVID with CD21(low) B-cell expansion resemble anergic B cells based on high constitutive pERK expression. The IgM(+) memory B cells of these patients, especially those that are CD21(low), have a defect in BCR endocytosis seemingly caused by dysregulated ERK signalin
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Reversion of anergy signatures in clonal CD21low B cells of mixed cryoglobulinemia after clearance of HCV viremia.
Full text linkHepatitis C virus (HCV) causes mixed cryoglobulinemia (MC) by driving clonal expansion of IgM+CD27+ B cells. These cells display both the features of anergy induced by continual engagement of the B cell receptor (BCR), such as high expression of phosphorylated extracellular signal regulated kinase (pERK) and reduced lifespan, and of virus-specific exhaustion such as CD21low phenotype and defective response to ligation of BCR and Toll-like receptor 9 (TLR9). Usually MC regresses after eradication of HCV with interferon, whose immunomodulatory activity might contribute to this effect. We investigated phenotypic and functional changes in clonal B cells of MC patients with sustained virologic responses to direct-acting antivirals (DAA), which lack immunomodulatory properties. We found that high pERK expression and accelerated apoptosis revert within 4 weeks after beginning therapy, whereas clonal B cells unresponsive to TLR9 stimulation persist for at least 24 weeks although they may partially rescue normal CD21 expression. Thus, similar to mouse models, features of anergy in MC B cells rapidly revert after disengagement from HCV, whereas virus-specific exhaustion imparts a durable inhibitory imprint on cell function. Treatment of HCV+ MC with DAA provides a valuable tool for untangling the molecular mechanisms of anergy and exhaustion in human B cells
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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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