Cluster Entry: Are Those Right Who Expect a Negative Selection of Member Firms?

2011 ◽  
Author(s):  
Daniel Grundgreif ◽  
Carola Jungwirth
Keyword(s):  
Negative Selection ◽  
Selection Of

scholarly journals A Role for Fas in Negative Selection of Thymocytes In Vivo

1998 ◽  
Vol 187 (9) ◽  
pp. 1427-1438 ◽  
Author(s):  
Hidehiro Kishimoto ◽  
Charles D. Surh ◽  
Jonathan Sprent
Keyword(s):  
Negative Selection ◽  
Cell Receptor ◽  
Staphylococcal Enterotoxin B ◽  
Thymic Medulla ◽  
Enterotoxin B ◽  
High Doses ◽  
Specific Peptide ◽  
Selection Of

To seek information on the role of Fas in negative selection, we examined subsets of thymocytes from normal neonatal mice versus Fas-deficient lpr/lpr mice injected with graded doses of antigen. In normal mice, injection of 1–100 μg of staphylococcal enterotoxin B (SEB) induced clonal elimination of SEB-reactive Vβ8+ cells at the level of the semi-mature population of HSAhi CD4+ 8− cells found in the thymic medulla; deletion of CD4+ 8+ cells was minimal. SEB injection also caused marked elimination of Vβ8+ HSAhi CD4+ 8− thymocytes in lpr/lpr mice. Paradoxically, however, elimination of these cells in lpr/lpr mice was induced by low-to-moderate doses of SEB (≤1 μg) but not by high doses (100 μg). Similar findings applied when T cell receptor transgenic mice were injected with specific peptide. These findings suggest that clonal elimination of semi-mature medullary T cells is Fas independent at low doses of antigen but Fas dependent at high doses. Previous reports documenting that negative selection is not obviously impaired in lpr/lpr mice could thus reflect that the antigens studied were expressed at only a low level.

Epitope mapping by negative selection of randomized antigen libraries displayed on filamentous phage 1 1Edited by J. Karn

1997 ◽  
Vol 269 (5) ◽  
pp. 704-718 ◽  
Author(s):  
Laurent Jespers ◽  
Stéphane Jenné ◽  
Ignace Lasters ◽  
Désiré Collen
Keyword(s):  
Negative Selection ◽  
Epitope Mapping ◽  
Filamentous Phage ◽  
Selection Of

scholarly journals Positive and negative selection of antigen-specific B cells in transgenic mice expressing variant forms of the VH1 (T15) heavy chain

2000 ◽  
Vol 12 (6) ◽  
pp. 873-885 ◽  
Author(s):  
James J. Kenny ◽  
Eric G. Derby ◽  
Jeffrey A. Yoder ◽  
Shawn A. Hill ◽  
Randy T. Fischer ◽  
...  
Keyword(s):  
B Cells ◽  
Transgenic Mice ◽  
Heavy Chain ◽  
Negative Selection ◽  
Selection Of

An extended ToxR POSSYCCAT system for positive and negative selection of self-interacting transmembrane domains

2007 ◽  
Vol 69 (2) ◽  
pp. 298-305 ◽  
Author(s):  
Eric Lindner ◽  
Stephanie Unterreitmeier ◽  
Anja N.J.A. Ridder ◽  
Dieter Langosch
Keyword(s):  
Negative Selection ◽  
Transmembrane Domains ◽  
Selection Of

scholarly journals Modeling colicin operons as genetic arms in plasmid-genome conflicts

2021 ◽  
Author(s):  
Pavithra Anantharaman Sudhakari ◽  
Bhaskar Chandra Mohan Ramisetty
Keyword(s):  
Negative Selection ◽  
Bacterial Genome ◽  
Evolutionary Perspective ◽  
Bacterial Genomes ◽  
Sequence Analyses ◽  
Agent Based ◽  
Physiological Relevance ◽  
Maintenance Systems ◽  
Selection Of ◽  
Lethal Genes

Plasmids are acellular propagating entities that depend, as molecular parasites, on bacteria for propagation. The conflict between the bacterial genome and the parasitic plasmids allows the emergence of genetic arms such as Colicin (Col) operons. Endonuclease Col operons encode three proteins; an endonuclease colicin (cleaves nucleic acids), an immunity protein (inactivates its cognate colicin), and lysis protein (aids in colicin release via host cell lysis). Col operons are efficient plasmid-maintenance systems; (i) the plasmid cured cells are killed by the colicins; (ii) damaged cells lyse and releases the colicins that eliminate the competitors; and (iii) the released plasmids invade new bacteria. Surprisingly, some bacterial genomes have Col operons. The eco-evolutionary drive and physiological relevance of genomic Col operons are unknown. We investigated plasmidic and genomic Col operons using sequence analyses from an eco-evolutionary perspective. We found 1,248 genomic and plasmidic colicins across 30 bacterial genera. Although 51% of the genomes harbor colicins, the majority of the genomic colicins lacked a functional lysis gene, suggesting the negative selection of lethal genes. The immunity gene of the Col operon protects the cured host thereby eliminating the metabolic burden due to plasmid. We show mutual exclusivity of col operons on genomes and plasmids. We propose anti-addiction hypothesis for genomic colicins. Using a stochastic agent-based model, we show that the genomic colicins confer an advantage to the host genome in terms of immunity to the toxin and elimination of plasmid burden. Col operons are genetic arms that regulate the ecological interplay of bacterial genomes and plasmids.

Positive and Negative Selection of T Cells: A Transgenic Model

1989 ◽  
pp. 13-15
Author(s):  
W. C. Sha ◽  
Ch. A. Nelson ◽  
R. D. Newberry ◽  
D. M. Kranz ◽  
J. Russel ◽  
...  
Keyword(s):  
T Cells ◽  
Negative Selection ◽  
Transgenic Model ◽  
Selection Of
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