What percentage frequency are TCRs alphabeta heterodimer (as opposed to gammadelta)?
90%
Which of the following characteristics belong to TCRS:
a) long cytoplasmic domains
b) membrane bound
c) Secretory
d) short cytoplasmic domain
e) No cytoplasmic domain because its secreted
b) membrane bound
d) short cytoplasmic domain
What does TCR recognise?
Antigen as a complex of antigen peptide fragment with self MHC molecule
TCR have CDR like domains. True or false?
True
The TCR gene loci (alpha, beta, gamma, delta) is arranged very similarly to that of WHAT?
Immunoglobulin.
The arrangements of α/gamma loci are equivalent to the light chain and the arrangement of beta/delta are similar to the heavy chain.
Do the alpha/gamma chain gene loci have V, D and J or V and J?
V and J (and C)
Do the beta/delta chain gene loci have V, D and J or V and J?
V, D and J (and C)
Junction diversity happens in the genes for which molecules?
TCR and immunoglobulin
recombination signal sequences, 12/23 rule, RAG1-2 complex all the same
TCR has somatic mutation. True or false?
False, because no AID is expressed!!!
Why is it advantageous for T cell not to undergo somatic mutations?
To prevent cytotoxic cells adapting to recognise epitopes presented on healthy cells.
What is CD3?
CD3 is the signalling complex which is the characteristic marker of T cell
How many subunits exist in the TCR signalling complex?
8
1 dimer in the TCR - alpha/beta
2 CD3 dimers - epsilon/delta gamma/epsilon
1 CD247 dimer - zeta/zeta (which exists primarily in the cytoplasm)
What are ITAMs?
Immunoreceptor tyrosine activation motifs which are involved in signalling.
In T cell co-stimulation what does B7 on the APC bind to?
CD28 on the T cell
What does CD28 binding to B7 lead to?
An activation signal which causes the T cell to make a cytokine called IL-2 (interleukin 2) which is a cytokine that drives proliferation of T cell, which can acts on itself and other T cells.
What does the inhibitory receptor CTLA-4 on the T cells bind to?
B7. If CTLA-4 is expressed by T cells then you get silencing and T cell shut down.
What the three main simplified steps in T cell activation?
1) Stimulation of naïve T cells (APC presents on MHC recognised by TCR)
2) T cells make IL-2
3) differentiate into Th or Tc cells
Once the T cells are activated they no longer require co-stimulation for a response. True or false?
True
What cells do T helper cells ‘help’?
B cells, macrophages
T helper cells that recognise MHC class 2 and antigen produce what?
Cytokines:
- these activate the B cell class switching
- interferon-gamma induces macrophages to have cytotoxic properties
What to Tc cells require to replicate?
IL-2, provided by Th cells hence Th controls the strength of the response.
Th cells are required to create memory cells from CTLs. True or false?
True
gammadelta T cells are mostly:
a) CD4-/8- or CD8+
b) CD4+/8+ or CD4+
a)CD4-/8- or CD8+
Where are gammadelta T cells mainly expressed?
Mucosal tissue (intraepithelial lymphocytes are predominantly gammadelta)
What percentage of T cells are gammadelta?
10%
alphabeta T cells mainly recognise peptides. What do gammadelta T cells mainly recognise?
lipid recognition
Do gammadelta T cells require antigen presentation on MHC?
No, they can either bind free antigens or antigens presented by non-classical MHC-like molecules.
What percentage of the T cells in the peripheral blood are CD1-restricted T cells?
0.1%
CD1 is a molecule similar to MHC. True or False.
True, they are structurally related
What do CD1-T cells recognise?
Lipid/glycolipids and other hydrophobic antigens
Describe the CD1 groove.
Deep and hydrophobic (good for binding lipids)