IAI - T cells, effector functions and the MHC

Question 1

Peptides are displayed by cells in what context?

Answer 1

Peptides are displayed by cells in the context of highly polymorphic MHC molecules.

Question 2

What structural property do both MHC I and MHC II share?

Answer 2

A peptide binding groove at the top

Question 3

describe the structure of an MHC1 molecule

Answer 3

MHC class I is a single chain molecule but on the cell surface it associates non covalently with another molecule known as beta-2 microglobulin.

Question 4

how is MHC1 molecule expressed?

Answer 4

expressed endogenously on all nucleated cells in the body.

Question 5

describe the structure of MHC11 molecules

Answer 5

an alpha-beta heterodimer

Question 6

how is MHC11 expressed?

Answer 6

• expressed on specialised antigen presenting cells:
  
  • monocytes
  • macrophages
  • dendritic cells
  • b lymphocytes

Question 7

What is the functional role of MHC I?

Answer 7

• cell becomes infected
• host breaks down sample of all proteins being produced using proteasome
• proteasome takes peptides and transports them to ER
• loaded onto newly synthesised MHC1 molecules
• These molecules are then loaded to the cells surface displaying the peptides to the immune system

Question 8

What is the functional role of MHC11

Answer 8

• A dendritic cell is taking up a bacterial antigen by endocytosis.
• The endocytic vesicles will contain proteolytic enzymes that will then degrade this protein.
• At the same time MHC II molecules are being synthesised and assembled in the endoplasmic reticulum
• These MHC class II molecules will migrate to late endosomes where they will fuse with the vesicles containing the degraded antigen.
• It’s in these vesicles that peptides are loaded into the MHC class II molecules.
• These peptide filled MHC class II molecules are then transported to the cell surface to be displayed by the rest of the immune system.

Question 9

Where are the genes encoding for MHC class I and II found?

Answer 9

short arm of chromosome 6

(this is the most polymorphic region of the whole genome)

Question 10

the short arm of chromosome 6 where the genes encoding for MHC 1 and 11 are found, is also called?

Answer 10

human leukocyte antigen or HLA.

Question 11

HLA class 1 has 3 distinct genes leading to 3 HLA proteins:

Answer 11

HLA-A
HLA-B
HLA-C

Question 12

HLA class 2 has 3 distinct genes leading to 3 HLA proteins:

Answer 12

HLA-DR
HLA-DQ
HLA-DP

Question 13

describe the structure of a t-cell receptor

Answer 13

• membrane-bound heterodimer
• two chains joined by disulphide bonds
• two chains encoded by different genes
• two subtypes alpha-beta and gamma-delta

consist of variable and constant domains

Question 14

Where is the greatest variability in T-cell receptors?

Answer 14

• In the receptor binding groove.
• These parts of the T-cell receptor reach down and make contact with the peptide MHC molecule.

Question 15

what class does CD8 bind to?

Answer 15

CD8 binds with MHC CLASS 1

Question 16

what class does CD4 bind to?

Answer 16

CD4 binds with MHC CLASS 2

Question 17

What does the activation of t cells require

Answer 17

two signals

signal 1 = activation of T cell
signal 2 = co-stimulation when CD86 on APC surface binds to CD28 on T cell surface

Question 18

What is a naive T-cell?

Answer 18

A T cell that has never encountered the peptide MHC molecule that can activate it.

Question 19

What do Th1 cells secrete and what do Th 1 cells do

Answer 19

secrete interferon gamma (IFN-γ) and IL-2

• allows CD8 T cells to proliferate, it also allows them to differentiate and start to express the cytolytic cytokines ** perforins and granzymes.
• aid macrophage function via the secretion of interferon gamma.

Question 20

what cytokines do Th2 cells produce?

Answer 20

IL4 and IL13

Question 21

whats the function of Th2?

Answer 21

provides help for B cells

Question 22

whats the function of Th17

Answer 22

helps fight extracellular pathogens

Question 23

what cytokines do Th17 cells produce?

Answer 23

IL-17
IL-21
IL-22

Question 24

Whats the 5 functions of Treg cells?

Answer 24

• suppress stimulatory activity of APC
• suppress proliferation of responder cells
• suppress cytokine production of responder cells
• suppress antibody production from B cells
• suppress functions of NK + NKT cells

Question 25

do keats quiz on t-cells, effector functions, and the MHC

Answer 25

https://keats.kcl.ac.uk/mod/lesson/view.php?id=7651854

Question 26

How do the sources of peptides loaded into MHC class I and II differ?

Answer 26

• Generally MHC class I molecules will present peptides derived from proteins currently being synthesised in that cell.
• MHC class II (generally expressed on specialised antigen presenting cells) will present peptides derived from antigens that they’ve pulled in from outside.

Question 27

What is the difference between what MHC I and MHC II molecules display?

Answer 27

MHC II display exogenous antigens

MHC I displays endogenous antigens

Question 28

What happens once T-cells finish their rearrangement of their T-cell receptor?

Answer 28

Unlike B cells in which immunoglobulin genes can then undergo affinity maturation, once the T-cells finish rearrangement of their T-cell receptor, it’s not able to change that configuration at all.

Question 29

What does the tripartite interaction between the T-cell receptor with the combination of the peptide and MHC determine?

Answer 29

determines whether a particular T-cell will respond to a particular peptide presented by a particular MHC molecule.

Question 30

T cells and B cells only recognise peptides presented by molecules encoded by genes of the major histocompatibility complex (MHC)

true or false, and why

Answer 30

FALSE - key word here is ‘only’

B cells can recognise a variety of antigens including proteins and carbohydrates with no need for antigen presentation.

T cell require MHC to recognise peptides

Question 31

what number is CD on the T-cell, compared to the APC

Answer 31

t-cell (either CD4 or CD8) has CD28

APC has CD80 OR CD86

Question 32

Which one is a co-stimulatory molecule, CD28 or CD86

Answer 32

CD28 is a costimulatory molecule on T cells.

Question 33

how do CD8 T-cells kill target cells?

Answer 33

by release of granzyme and perforin into the target cells.

Perforins create holes in the target cell’s membrane, allowing granzymes to enter the target cell.