Flashcards in "Microbiology/Immunology T Cell Receptors" SANA Deck (35):
What types of cells do CD4 cells target and why?
CD4 cells target macrophages and B-cells to activate cytokines and antibody production respectively
Why types of cells do CD8 cells target and why?
CD8 cells target virus infected cells to kill them.
How many antigen binding sites does a T-cell receptor have?
All of the following are differences between T-cell receptors (TCRs) and B-cells receptors (BCRs), except:
a. TCRs are found only on cells surfaces
b. Only BCRs go through somatic mutations in their development to lead to higher antigen affinity than TCRs
c. Only BCRs have variable regions
d. TCRs see short peptide fragments in the antigens presented by MHC, while BCRs see surface structures
e. TCRs have higher diversity than BCRs.
C: both BCRS and TCRs have both constant and variable regions.
Why is the T-cell receptors only present on the surface of the cell?
Because they are transmembrane molecules and thus insoluble.
A TCR molecule is a ______-linked heterodimer.
What are two responsibilities of the TCR complex?
Escort the T-cell receptor chains to the surface and makes signal transduction possible
Your new patient has a rare disease where his CD3 supply is specifically depleted. What change would you expect in his T-cell receptors?
The T-cell receptors would not be able to reach the surface of the cells as CD3 is required for this. Thus, they probably would not function and his ability to destroy virus-infected cells and activate cytokines and antibodies would be compromised.
What makes up the TCR complex?
CD3 + TCR + (Z-chains)
All of the following generate diversity in T-cell receptors, except:
a. P and N nucleotide addition
b. different combinations of TCR chains
c. gene segments being joined imprecisely
d. somatic mutations
e. recombinations of different gene segments.
d: somatic mutations only happen in B-cell receptor development
Between TCRs and BCRs: which has higher affinity for antigens? Which has greater diversity?
BCRs have higher affinity and TCRs have higher diversity (because of highers numbers of Joining (J) segments) .
Why is higher diversity extremely important for T-cell receptors?
TCRs have to recognize peptides from any pathogens they encounter, including ones that they are seeing for the first time.
What is the difference in the ways in which BCR and TCR recognizes antigen?
BCRs recognize surface structures such as carbohydrates, lipids etc., while TCRs recognize short peptide fragments.
TCR affinity for peptide + MHC is _______ (weak/strong) compared to antibodies because antibodies perform ________
weak; somatic mutations
Which of the MHC classes is more polymorphic, with shorter peptides?
A single MHC molecule can bind multiple peptides as long as they share:
a. similar surface structures
b. exactly the same amino acid chains
c. certain sequences and motifs
d. similar alpha and beta chains
alpha chain of MHC II is ___________ (polymorphic/monomorphic)
Researchers have found that the MHC Class I molecule can bind both the HIV reverse transcriptase and the influence A nucleoprotein peptide despite coming from difference viruses. What is a reasonable explanation for this?
Both the HIC reverse transcriptase and the influence A peptide must share a common peptide motif which the MHC class I can recognize.
In order to recognize a the presentation of an antigen, it is necessary that the T-cell recognize:
a. both the antigen and the MHC
b. only the antigen
c. only the MHC
What are the two modes of recognition in alloreactivity?
Peptide-dominant binding and MHC-dominant binding
What MHC class can you expect to find on liver and kidney cells as well as on neutrophils, dendritic cells, macrophages etc.?
MHC class I as it is expressed on all nucleated cells.
MHC Class II is present on (hint: more than one choice is correct):
a. all nucleated cells
b. professional antigen presenting cells
c. some hematopoetic and thymic stromal cells
d. red blood cells
b and c
Autoimmunity can occur by a mechanism in which an MHC class is upregulated in target organs. Which MHC class is this likely?
MHC Class II, as it occurs only in select few hematopoetic and antigen presenting cells normally.
Which co-receptor on T-cells functions to interact with MHC Class I? what about MCHl class II
class I: CD8
class II: CD4
The gamma-delta TCR is different from other TCRs in that it can recognize the MHC and antigen___:
a. separately, if even one is present
In regards to MHC genes, a person with a heterozygous haplotype will be able to present ______ (more/less) peptides from diverse pathogens
more as they will be able to present more peptides from any pathogens.
If the relative risk of an allele is greater than 1 with respect to a disease, what does it mean for people who carry that allele?
It means that there is an association of that allele with the disease.
Cytosolic pathogens are usually degraded in the ______ by binding to MHC class _____, resulting in _________
cytosol, I, cell death
What do intravesicular pathogens and extracellular pathogens and toxins have in common:
a. both are degraded in the cytosol
b. both are degraded in endocytotic vesicles
c. both are presented by MHC class II cells to CD4 T-cells
d. both result in cell death
e. both b and c
Extracellular pathogens are unique in that their presentation to TCRs results in the activations of ______ cells
B-cells which secrete Ig
Name two differences between MHC class I and MHC class II processing of antigens.
1. In class I processing, the antigen is ubiquinated before being fragmented by proteases. In Class II the antigen is fragmented by the proteases in the phagolysosome.
2. In class I, the fragments are then moved in to the ER lumen. In class II, the peptide moves into endosomal compartment, where CLIP is displaced from MHC class II brinding groove. CLIP prevents binding of self-peptides.
It is possible for MHC class I molecules to present exogenous peptides?
Yes, because there is evidence of cross-presentation between class I and class II
What are superantigens?
They act as a bridge between TCR and MHC, stimulating a high percentage of T-cells bearing certain V genes.
Which of the following are NOT required in superantigen function.
a. required processing
b. MHC restricted recognition
c. binding of MHC peptide groove
d. all of the above