T-cells, Effector Functions and MHC

Question 1

What are the X2 main types of T-cell?

What do each type do?

Answer 1

CD4 = can differentiate into different effector T-cell types

CD8 = are cytotoxic cells that kill target cells

Question 2

What molecule is used by antigen presenting cells to present small fragment peptides of antigens on their surface?

What is the name of the complex formed by these two molecules?

Answer 2

Major histocompatability complex

Peptide-MHC complex

Question 3

What are the X2 types of MHC molecule?

How do these differ?

Answer 3

MHC 1 = single chain = found on all cells

MHC 2 = alpha/beta heterodimer = found on entire presenting cells only

Question 4

What is the area at the top of the MHC which the antigen peptide fragment sits in called?

Answer 4

Peptide binding groove

Question 5

Where do the peptides displayed on the MHC moelcuels come from in:

A) MHC class 1 molecules 
B) MHC class 2 molecules

Answer 5

A) MHC class 1 molecules 
= peptides displayed are derived from proteins that cell is currently synthesising (so if a virus hijacks the cell machinery to synthesis it’s own proteins for reproduction, these will be displayed)

B) MHC class 2 molecules 
= peptides displayed are derived from antigens that the cell has phagocytosed and broken down.

Question 6

Where is the gene located which encodes for the MHC classes?

What is this region called?

Answer 6

On the P arm of chromosome 6

The human leukocyte antigen region

Question 7

What are the X3 possible HLA 1 genes (code for MCH 1)?

Answer 7

HLA A
HLA B
HLA C

Question 8

What are the X3 possible HLA 2 genes (code for MCH 2)?

Answer 8

HLA DP
HLA DQ
HLA DR

Question 9

What defines a T-cell?

Answer 9

Having a T-cell receptor!

Question 10

What joins the X2 chains of a T-cell?

Answer 10

Disulphide bonds

Question 11

Do T-cells undergo affinity maturation?

Answer 11

No, only B-cells.

They both however undergo gene rearrangement.

Question 12

What class of MHC presented peptides do CD8 (cytotoxic) T-cells interact with?

Answer 12

Their CD8 receptor interacts with the conserved (non-peptide binding region) of MHC 1 molecules.

Question 13

What class of MHC presented peptides do CD4 (T-helper) T-cells interact with?

Answer 13

Their CD4 receptor interacts with the conserved (non-peptide binding region) of MHC 2 molecules.

Question 14

How many signals are needed to activate T-cells?

Answer 14

X2

1) MHC-peptide complex
2) co-stimulators signal

Question 15

Give X2 examples of second signals / co-stimulators signals displayed by antigen presenting cells?

Answer 15

CD80

CD86

Question 16

What do second signals such as CD80 or CD86 bind to on the T-cell which (when they have both bound together) sends a signal to the T-cell to activate it?

Answer 16

A molecule called CD28

Question 17

How do CD8 T-cells work?

Answer 17

They are cytotoxic T-cells therefore they bind to antigen presenting cells and release cytotoxic cytokines to kill it.

Question 18

What different kinds of effector T-cells can CD4 (T-helper) cells differentiate into once activated?

What cytokines do each secrete?

Answer 18

Th1 = secrete IFN gamma, IL2
Th2 = IL2, 4, 5, 13
Th17 = IL 17, 21, 22
Treg = IL10, TGF beta

Question 19

What do activated Th1 T-helper cells do?

Answer 19

They secrete:

INF gamma = promote macrophage activation and direction to sites of infection

IL2 = helps CD8 cytotoxic T-cell differentiation

Question 20

What do activated Th2 T-helper cells do?

Answer 20

They secrete IL2, 4, 5 and 13 which helps B-cells to divide/class switch/affinity mature/differentiate into plasma cells.

Question 21

What do activated Th17 T-helper cells do?

Answer 21

They secrete IL17, 21 and 22 which attract neutrophils to the site of infection via chemotaxis.

Question 22

What do activated T-reg cells do?

Answer 22

They secrete IL10 and TGF beta (but also work via cell to cell contact) which mainly SUPPRESSES the antigen presenting cell activity therefore mediates the inflammatory response.