Lecture 12: T-Cell Development and MHC

Question 1

γδ T cells never express ________.

Answer 1

CD4 or CD8

Question 2

Outline the T-Cell selection process:

Answer 2

Positive:
- TCR engages in a low-affinity interaction with self MHC = Maturation
Lack of Positive:
- TCR does not interact with self MHC at all = Apoptosis
Negative:
- TCR engages in a high-affinity interaction with self MHC = Apoptosis

Question 3

Unlike BCR and antibodies, which recognise their cognate antigens in their ___________, TCR can only recognize their cognate antigen as _________________.

Answer 3

Native form

Short peptides bound to MHC

Question 4

What do Th1 cells do?

Answer 4

• Activate MO to stimulate Microbicidal activity

- Induce class switching of activated B-cells

Question 5

What do Th2 cells do?

Answer 5

• Induce class switching of activated B-cells

Question 6

Describe the structure of an Antibody:

Answer 6

• Fab fragment is an S-S linked heterodimer, each chain has an IgC and IgV domain
• Ag binding site is at the juxtaposition of the V regions

Question 7

Describe the structure of the TCR:

Answer 7

• S-S linked heterodimer, each chain has an IgC-like and IgV-like domain
• Ag binding site is the juxtaposition of the Vα and Vβ regions

Question 8

In the V region of each TCR chain there are ______________ or ______________________. The primary Ag recognition domain is ______.

Answer 8

3 Hypervariable
Complementarity Determining Regions (CDRs)
CDR3

Question 9

The TCRα locus is on chromosome ___ and consists of ___________.

Answer 9

14

70-80 V, 61 J, and 1 C regions

Question 10

The TCRα locus is on chromosome ___ and consists of ___________.

Answer 10

7

52 V, 1 D, 6-7 J and 1 C regions

Question 11

MHC class 1 presents _________ or __________ Ag from ___________ pathogens.

Answer 11

Intrinsic or Endogenous

Intracellular

Question 12

MHC class 2 presents _________ or __________ Ag from ___________ pathogens.

Answer 12

Extrinsic
Exogenous
Extracellular

Question 13

MHC class one is expressed on _____________________________

Answer 13

All uncleared cells, especially highly expressed on HSC

Question 14

MHC class 2 can be expressed on cells other than ______ in response to ______

Answer 14

APC

IFN-γ

Question 15

Human MHC locus is on chromosome ___

Answer 15

6

Question 16

The MHC that a cell expresses determines what _______________ and to which _________ they present to

Answer 16

Peptide antigen

T-Cell

Question 17

What are the key features of MHC class 1?

Answer 17

• heavy chain α bound to β2 micro globulin
• α1 and α2 domains form the antigen binding site
• binds peptides 8-10aa long, ends are bound

Question 18

What are the key features of MHC class 2?

Answer 18

• heterodimers of α and β chains
• No β2 microglobulin
• binds peptides that are >13aa long, ends not bound

Question 19

The ______ region on MHC class 1 binds to CD8

Answer 19

α3

Question 20

The ______ region on MHC class 2 binds to CD4

Answer 20

β2

Question 21

Class 1 MHC has 6 _________________ which convey specificity

Answer 21

Binding pockets

Question 22

What is the function of CD4 and CD8?

Answer 22

Their binding to the membrane-proximal domains on MHC is required to produce an effective response

Question 23

What are super antigens?

Answer 23

Molecules produced by many pathogens that are recognised by T-Cells without being processed into peptides and presented on MHC

Question 24

Super antigens bind to _____________________________

Answer 24

Outside of MHC class 2

Question 25

Stimulation by a super antigen causes _____ to release ___________________________

Answer 25

CD4s to release large amounts of cytokines

Question 26

What is immunodominance?

Answer 26

Immunodominant peptides bind the best to available MHC

Question 27

What determines Immunogenicity?

Answer 27

• the ability of the antigen processing pathway to generate peptides from the proteins
• presence of Ag specific T-Cells

Question 28

What is Heterologous Immunity?

Answer 28

Memory cells specific for one pathogen may be activated by an unrelated pathogen if it has a similar epitope