"Microbiology/Immunology T Cell Receptors" SANA

Question 1

What types of cells do CD4 cells target and why?

Answer 1

CD4 cells target macrophages and B-cells to activate cytokines and antibody production respectively

Question 2

Why types of cells do CD8 cells target and why?

Answer 2

CD8 cells target virus infected cells to kill them.

Question 3

How many antigen binding sites does a T-cell receptor have?

Answer 3

One

Question 4

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.

Answer 4

C: both BCRS and TCRs have both constant and variable regions.

Question 5

Why is the T-cell receptors only present on the surface of the cell?

Answer 5

Because they are transmembrane molecules and thus insoluble.

Question 6

A TCR molecule is a ______-linked heterodimer.

Answer 6

Disulfide

Question 7

What are two responsibilities of the TCR complex?

Answer 7

Escort the T-cell receptor chains to the surface and makes signal transduction possible

Question 8

Your new patient has a rare disease where his CD3 supply is specifically depleted. What change would you expect in his T-cell receptors?

Answer 8

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.

Question 9

What makes up the TCR complex?

Answer 9

CD3 + TCR + (Z-chains)

Question 10

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.

Answer 10

d: somatic mutations only happen in B-cell receptor development

Question 11

Between TCRs and BCRs: which has higher affinity for antigens? Which has greater diversity?

Answer 11

BCRs have higher affinity and TCRs have higher diversity (because of highers numbers of Joining (J) segments) .

Question 12

Why is higher diversity extremely important for T-cell receptors?

Answer 12

TCRs have to recognize peptides from any pathogens they encounter, including ones that they are seeing for the first time.

Question 13

What is the difference in the ways in which BCR and TCR recognizes antigen?

Answer 13

BCRs recognize surface structures such as carbohydrates, lipids etc., while TCRs recognize short peptide fragments.

Question 14

TCR affinity for peptide + MHC is _______ (weak/strong) compared to antibodies because antibodies perform ________

Answer 14

weak; somatic mutations

Question 15

Which of the MHC classes is more polymorphic, with shorter peptides?

Answer 15

MHC I

Question 16

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

Answer 16

c

Question 17

alpha chain of MHC II is ___________ (polymorphic/monomorphic)

Answer 17

monomorphic

Question 18

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?

Answer 18

Both the HIC reverse transcriptase and the influence A peptide must share a common peptide motif which the MHC class I can recognize.

Question 19

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

Answer 19

a

Question 20

What are the two modes of recognition in alloreactivity?

Answer 20

Peptide-dominant binding and MHC-dominant binding

Question 21

What MHC class can you expect to find on liver and kidney cells as well as on neutrophils, dendritic cells, macrophages etc.?

Answer 21

MHC class I as it is expressed on all nucleated cells.

Question 22

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

Answer 22

b and c

Question 23

Autoimmunity can occur by a mechanism in which an MHC class is upregulated in target organs. Which MHC class is this likely?

Answer 23

MHC Class II, as it occurs only in select few hematopoetic and antigen presenting cells normally.

Question 24

Which co-receptor on T-cells functions to interact with MHC Class I? what about MCHl class II

Answer 24

class I: CD8
class II: CD4

Question 25

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
b. together

Answer 25

a

Question 26

In regards to MHC genes, a person with a heterozygous haplotype will be able to present ______ (more/less) peptides from diverse pathogens

Answer 26

more as they will be able to present more peptides from any pathogens.

Question 27

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?

Answer 27

It means that there is an association of that allele with the disease.

Question 28

Cytosolic pathogens are usually degraded in the ______ by binding to MHC class _____, resulting in _________

Answer 28

cytosol, I, cell death

Question 29

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

Answer 29

e

Question 30

Extracellular pathogens are unique in that their presentation to TCRs results in the activations of ______ cells

Answer 30

B-cells which secrete Ig

Question 31

Name two differences between MHC class I and MHC class II processing of antigens.

Answer 31

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.

Question 32

It is possible for MHC class I molecules to present exogenous peptides?

Answer 32

Yes, because there is evidence of cross-presentation between class I and class II

Question 33

What are superantigens?

Answer 33

They act as a bridge between TCR and MHC, stimulating a high percentage of T-cells bearing certain V genes.

Question 34

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

Answer 34

d

Question 35

What is the root cause of the toxic shock syndrome?

Answer 35

overproduction of cytokines (IL2 and IL4)