Chapter 9 Thymus derived T cells. Flashcards
What do T cell precursors differentiate into?
immunocompetent T cells in the thymus,
Then they populate the peripheral lymphoid organs and tissues
T cells make up ___ of recirculating pool of small lymphocytes?
80%
How long can T cells live?
They are relatively long lived cells that may survive from 6 months to over 20 years
What does a developing T cell acquire in the thymus?
antigen specific receptors and other functional phenotypic characteristics that mark it as a mature T cell.
Mature T cells express a variety of cell surface proteins. Among them are proteins involved in?
- ) Antigen recognition
- ) signal transduction
- ) adhesion to APC and target cells
Activation of a cell surface receptor requires binding of ….?
binding to its specific ligand, which may be a counter receptor on another cell or a soluble protein ( cytokine)
What are Accessory Molecules?
they are cell membrane proteins which play a critical role in T cell response to antigen. Some are adhesion molecules, others deliver signals to the T cell that function with signals from the TCR-CD3/zeta zeta complex, to fully activate the T cell.
What do CD4 and CD8 molecules do?
they promote adhesion of Tcells to APCs and Target cells and also play a role in signal transduction, thereby potentiating T cell activation.
Where is CD4 molecules found?
on helper T cells. It binds to the Beta 2 domain of the class II MHC molecules on the surface of professional APCs
Where is CD8 molecules found?
on Cytotoxic T cells. It function is the recognition of the Alpha 3 domain of class 1 MHC, enabling cytotoxic cells to bind to target cells.
What do Lymphocyte adhearence molecules do?
they strengthen interactions between helper T cells and professional APCs or cytotoxic T cells and Target cells.
What does CD11aCD18 do?
binds T cells to CD54 molecules (ICAM -1) on APCs and target cells. Promotes the binding of T cells to endothelial cells during T cell extravasation.
What does CD2 (LFA-2) do?
found on mature T cells. CD2 binds to a protein called CD58 (LFA-3) present on APCs and Target cells. CD2 functions both as an intercellular adhesion molecule and as a T cell signal transducer.
T/F?
CD28 is a constitutively expressed membrane receptor for co- stimulatory signals (Signal -1)
FALSE BITCHES- SIGNAL-2
CD28 is a constitutively expressed membrane receptor for co- stimulatory signals (Signal -2) . Its ligand is B7-1 (CD80) and B7-2 (CD86) cell surface proteins that are expressed on professional APCs.
Who delivers signal 1?
the TCR complex
what is TCR alpha Beta and what kind of tail do they have?
they are integral membrane proteins with an extracellular domain, a transmembrane domain, and a short cytoplasmic tail
Where do the CDRs reside on the TCR alpha Beta?
in the variable regions
What CDR displays the most diversity on the TCR Alpha Beta chain?
CDR3- its in the center and displayes the most diversity it is a product of junctional diversity. and directly interacts with antigenic peptide, while CDR1 ( interacts with both peptide and MHC) and CDR2 (Interacts with MHC)
What is a superantigens and where can they bind?
a super antigen is are soluble bacteria proteins which bind simultaneously to all TCRS bearing certain specific Vβ domains –( No need for antigen processing)
and they bind to the Beta chain on the V domain which has the CDR4
what does clonotypic mean?
recognize only a single epitope on an MHC protein.
TCRs are clonotypic
What does allelic exclusion control?
the genetic expression of TCRs.
Who regulates the rearrangement of TCrR gene segments and BCR gene segments
several enzymes collectively called recombinases.
RAG 1 and RAG 2 are only found where?
in T and B lymphocytes, they are only active in developing lymphocytes, which explains why TCR rearrangement do not continue in mature T and B cells that have completed gene rearrangements.
How is DNA repair enzymes different from RAG proteins?
these enzymes are expressed in many cell types.
their role in Immunoglobulin (BCR) gene recombination is to repair the double stranded breaks made by RAG