The Molecular Basis of Thymocyte Positive Selection and CD4/CD8 Lineage Commitment

1998 ◽  
pp. 485-502
Author(s):  
Cynthia J. Guidos
Keyword(s):  
Positive Selection ◽  
Molecular Basis ◽  
Lineage Commitment

The Molecular Basis of B-cell Lineage Commitment

1999 ◽  
Vol 64 (0) ◽  
pp. 51-60 ◽  
Author(s):  
S.L. NUTT ◽  
A.G. ROLINK ◽  
M. BUSSLINGER
Keyword(s):  
B Cell ◽  
Molecular Basis ◽  
Cell Lineage ◽  
Lineage Commitment

scholarly journals Early Growth Response (Egr)-1 Gene Induction in the Thymus in Response to TCR Ligation During Early Steps in Positive Selection Is Not Required for CD8 Lineage Commitment

2000 ◽  
Vol 165 (5) ◽  
pp. 2444-2450 ◽  
Author(s):  
M. Albert Basson ◽  
Timothy J. Wilson ◽  
Giuseppe A. Legname ◽  
Nitza Sarner ◽  
Peter D. Tomlinson ◽  
...  
Keyword(s):  
Positive Selection ◽  
Growth Response ◽  
Gene Induction ◽  
Early Growth ◽  
Lineage Commitment ◽  
Early Growth Response

scholarly journals The Absence of Itk Inhibits Positive Selection Without Changing Lineage Commitment

2002 ◽  
Vol 168 (12) ◽  
pp. 6142-6151 ◽  
Author(s):  
Julie A. Lucas ◽  
Luana O. Atherly ◽  
Leslie J. Berg
Keyword(s):  
Positive Selection ◽  
Lineage Commitment

scholarly journals An antagonist peptide mediates positive selection and CD4 lineage commitment of MHC class II–restricted T cells in the absence of CD4

2005 ◽  
Vol 201 (1) ◽  
pp. 149-158 ◽  
Author(s):  
Henry Kao ◽  
Paul M. Allen
Keyword(s):  
T Cells ◽  
Positive Selection ◽  
Mhc Class Ii ◽  
Cell Receptor ◽  
Peptide Ligands ◽  
Lineage Commitment ◽  
Altered Peptide Ligands ◽  
Specific Contribution ◽  
Selection Of

The CD4 coreceptor works together with the T cell receptor (TCR) to deliver signals to the developing thymocyte, yet its specific contribution to positive selection and CD4 lineage commitment remains unclear. To resolve this, we used N3.L2 TCR transgenic, RAG-, and CD4-deficient mice, which are severely impaired in positive selection, and asked whether altered peptide ligands can replace CD4 function in vivo. Remarkably, in the presence of antagonist ligands that normally deleted CD4+ T cells in wild-type mice, we induced positive selection of functional CD4 lineage T cells in mice deficient in CD4. We show that the kinetic threshold for positive and negative selection was lowered in the absence of CD4, with no evident skewing toward the CD8 lineage with weaker ligands. These results suggest that CD4 is dispensable as long as the affinity threshold for positive selection is sustained, and strongly argue that CD4 does not deliver a unique instructional signal for lineage commitment.

scholarly journals Positive Darwinian selection results in resistance to cardioactive toxins in true toads (Anura: Bufonidae)

2009 ◽  
Vol 5 (4) ◽  
pp. 513-516 ◽  
Author(s):  
David J. Moore ◽  
Damien C. T. Halliday ◽  
David M. Rowell ◽  
Anthony J. Robinson ◽  
J. Scott Keogh
Keyword(s):  
Positive Selection ◽  
Molecular Basis ◽  
Positive Darwinian Selection ◽  
Binding Region ◽  
Independent Evidence ◽  
The Family ◽  
Cardioactive Steroids ◽  
Distinct Sequence ◽  
Evolution Of Resistance ◽  
Homologous Amino Acid

Members of the Family Bufonidae, true toads, are famous for their endogenously synthesized cardioactive steroids that serve as defensive toxins. Evolution of resistance to these toxins is not understood. We sequenced a key region of the toxin's binding site in the Na + /K + ATPase for relevant taxa representing Hyloidea (including bufonids), Ranoidea and Archaeobatrachia and tested for positive selection in a phylogenetic context. Bufonidae were distinct from other Hyloidea at 4–6 of 12 sites and, with one exception, had a homologous amino acid sequence. Melanophryniscus stelzneri had a distinct sequence, consistent with other independent evidence for a differentiated toxin. Tests within Bufonidae detected positive selection within the binding region, providing, to our knowledge, the first evidence of this type for positive selection within Amphibia. There was no evidence for positive selection on Bufonidae or M. stelzneri lineages. Sequence change in Leptodactylus ocellatus , a leptodactylid predator of Bufonidae, provides a molecular basis for predator resistance possibly associated with gene duplication.

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