T Cell Recptor

Question 1

What do T cells recognize?

Answer 1

Linear peptide fragments bound to either MHC I or MHC II on APCs

Question 2

What is the structure of the TCR?

Answer 2

It is a disulfide linked heterodimer of glycoproteins that have both constant and variable regions.

Question 3

What type of membrane protein is the TCR?

Answer 3

It is a transmembrane protein

Question 4

What generates T cell diversity?

Answer 4

1- Somatic recombination of V, D, and J segments
2- recombination of different number of gene segments
3- Imprecise joining of segments
4- “P” and “N” nucleotide addition via TdT
4- assembly of different combination of rearranged TCR chains

Question 5

What are the different TCR chains?

Answer 5

alpha, beta, gamma, and delta

Question 6

Which TCR chains only have V and J segments?

Answer 6

alpha and gamma

Question 7

Which TCR chains have V, D, and J segments?

Answer 7

beta and delta

Question 8

What do T cells monitor?

Answer 8

The intracellular environment of the hos cell

Question 9

Describe the affinity of T cells for MHC and peptide?

Answer 9

It is a very low affinity

Question 10

What is the function of CD4 and CD8?

Answer 10

they are co-receptors that increase the affinity of T cells for the APC

Question 11

What do CD4 and CD8 interact with?

Answer 11

Constant regions of the MHC class I and MHC class II

Question 12

What comprises an entire TCR complex?

Answer 12

1- TCR
2- MHC
3- CD4 or CD8

Question 13

Describe the action of superantigens

Answer 13

Bacterial exotoxins non-specific activation of T-cells resulting in polyclonal T cell activation and massive cytokine release

Question 14

What is involved in a superantigen complex?

Answer 14

“Gluing” together the TCR and MHC in a NON-SPECIFIC manner

Question 15

What are three differences between superantigens and normal antigens?

Answer 15

1- Do not have MHC restricted recognition
2- Do not need to be processed
3- Do not bind to a peptide groove in MHC

Question 16

What type of cells express MHC class I? Give some examples.

Answer 16

All nucleated cells. Examples include- T cells, B cells, Macrophages, Neutrophils, hepatocyts, kidney cells, brain cells

Question 17

What type of cells express MHC class II? Give examples.

Answer 17

MHC class II is expressed on a subset of hematopoietic cells and thymic stromal cells. Examples include- B cells, Macrophages, Langerhans presenting cells, epithelial cells of the thymus

Question 18

What is the structure of MHC class I?

Answer 18

3 alpha and 1 beta

Question 19

Where is the peptide binding cleft in MHC class I?

Answer 19

In between alpha 1 and alpha 2

Question 20

What is the structure of MHC class II?

Answer 20

2 alpha and 2 beta

Question 21

Where is the peptide binding cleft in MHC class II?

Answer 21

Alpha 1 and beta 1

Question 22

In MHC class II, what subunits implant in the membranes

Answer 22

alpha 2 and beta 1 heterodimer

Question 23

Which MHC class recognizes larger peptide fragment?

Answer 23

MHC class II

Question 24

Describe the MHC class I antigen processing pathway

Answer 24

1- cytoplasmic protein is ingested by a proteosome
2- peptide is taken to the ER
3- MHC class I is in the ER with chaperones bound
4- When MHC class I sense antigen in the ER the chaperones come off
5- Peptide/ MHC complex makes it way through the default pathway to the cell surface

Question 25

Describe the MHC class II antigen processing pathway

Answer 25

1- Antigen is taken up into the cell bia phagocytosis
2- acidification of the endosome activates proteases in the vesicle
3- antigen is degraded into peptide fragments
4- Vesciles containing peptides fusewith vesicles containing MHC class II molecures
5- Expressed on cell surface