T-cell Receptor

Question 1

What is a TCR?

Answer 1

It is a membrane-bound heterodimer of either alpha or beta chains or gamma and delta chains

Question 2

How are the two chains held together?

Answer 2

Disulphide linkage

Question 3

What does each chain posses?

Answer 3

A transmembrane domain and a short cytoplasmic tail

Question 4

What is the transmembrane region rich in? What does this allow for?

Answer 4

It is rich in positive amino acids which allows the association of other molecules

Question 5

How is TCR Ag recognition mediated?

Answer 5

By the V domain of both peptide chains

Question 6

What does the Ag contact on the TCR?

Answer 6

3 hypervariable loops (CDR1-3)

Question 7

In addition to the 3CDR regions, what stabilizes the structure?

Answer 7

Hypervariable loop 4 (HV4) contributes to Ag recog. and stabilizes structure

Question 8

What must occur for the TCR to recognize Ag?

Answer 8

The Ag has to be presented in the context of the correct MHC

Question 9

What does the TCR contact?

Answer 9

The Ag and MHC

Question 10

What influences the TCR recognizing AG?

Answer 10

The surface of the MHC

Question 11

Why do some vaccines not work?

Answer 11

Some ppl don’t have the right MHC so the TCR can’t see the Ag

Question 12

What is the result of a TCR unable to engage the MHC?

Answer 12

Failure to recognize the bound Ag

Question 13

How are self restricted TCR generated?

Answer 13

Positive and negative selection of immature T-lymphocytes in the thymus

Question 14

What do my immature T cells see?

Answer 14

Everyone’s MHC

Question 15

What do my mature T cells see?

Answer 15

Only my MHC

Question 16

Why can a TCR not mediate intracellular signaling?

Answer 16

It has a short cytoplasmic tail

Question 17

How is Ag signaling facilitated in TCR?

Answer 17

By accessory molecules CD3

Question 18

What is CD3?

What does it do?

Answer 18

Transmembrane proteins with ITAM motifs on their cytoplasmic tails
The accessory molecule that mediates intracellular signaling in TCR

Question 19

What does CD3 have that allows it to cluster w/ TCR?

Answer 19

It has negatively charged residues in the transmembrane domain

Question 20

What are TCR co-receptors?

Answer 20

CD4 and CD8

Question 21

Where do co-receptors bind?

Answer 21

The invariant regions of the MHC molecules

Question 22

CD4 goes with which MHC class?

Answer 22

MHC class 2 (Killer)

Question 23

CD8 goes with which MHC class?

Answer 23

MHC class 1 (Helper)

Question 24

What increases the sensitivity to the Ag?

Answer 24

The co-receptors CD4 and CD8