T cells and co-ordinating the immune system

Question 1

How can we differentiate between T cells?

Answer 1

Based on phenotype.

Question 2

What are the phenotypes of T cells?

Answer 2

The molecules present within or external to the T cell.

Question 3

What is CD and what is it used for?

Answer 3

Class differentiation antigens present on T cells which correlate to their function.

Question 4

What is MHC restriction?

Answer 4

The specificity of MHC peptide transporter classes presenting antigen fragments to a specific T cell.

Question 5

How does MHC I restrict?

Answer 5

Macrophage engulfs the pathogen in the ER where it is broken down into fragments into the cytosol which is carried by MHC I to present to CD8+ T cells.

Question 6

How does MHC II restrict?

Answer 6

B cell antibodies bind to pathogen and forms a vesicle where it is degraded/ Macrophage takes in pathogen to form a phagosome where it is degraded. MHC II takes up antigen fragments in the endosome to present to CD4+ T cells.

Question 7

What is the function of CD4+ Tfh?

Answer 7

T follicular helper cells produce IL-21 to help B cell activation into plasma cells producing antibodies for antigen affinity. It is involved in the formation of germinal centres in lymphoid tissue.

Question 7

What is the function of CD4+ Tfh?

Answer 7

T follicular helper cells produce IL-21 to help B cell activation into plasma cells producing antibodies for antigen affinity. It is involved in the formation of germinal centres in lymphoid tissue.

Question 8

What is the function of CD4+ Th1 and CD8+?

Answer 8

Type 1 immunity to initiate phagocytic killing of a microbe causing tissue damage.

Question 9

What is the function of CD4+ Th2?

Answer 9

Type 2 immunity against helminths.

Question 10

What is the function of CD8+ CTL?

Answer 10

Cytotoxic killer which destroys infected host cells.

Question 11

What is the function of CD4+ Th17?

Answer 11

It recruits neutrophils for activation and directs autoimmunity. Releases IL-17.

Question 12

What is autoimmunity?

Answer 12

Antibodies target self cells.

Question 12

What is the function of CD4+ Treg?

Answer 12

Inhibits the response of T cells.

Question 13

What is IL-2 and what T cell produces it?

Answer 13

T cell survival and clonal expansion produced by Th2

Question 14

What is IFNy and what T cell produces it?

Answer 14

Responsible for macrophage activation, produced by Th2 and CD8+ T cells.

Question 15

What is IL-4 and what T cell produces it?

Answer 15

Regulating antibody production and haematopoeisis, released by Th2.

Question 16

What is IL-17 and what T cell produces it?

Answer 16

Activation of neutrophils, produced by CD4+ Th17

Question 17

What is Tfh and what T cell produces it?

Answer 17

B cell differentiation into plasma cells, produced by CD4+ Tfh.

Question 18

How do T cells activate and differentiate?

Answer 18

Interaction with the TCR by antigen processing, costimulation to determine it is pathogen derived by the pathogen itself or a dendritic or phagocytic cell and then cytokine release which stimulates differentiation.

Question 19

How can TCR be blocked?

Answer 19

By immunosuppressant drugs such as tacrolimus and cyclospoirin. They act in the cytoplasm to bind to the phosphotase enzyme calcineurine and prevent calcium-associated activation for transcription.

Question 20

What are the consequences of clonal expansion?

Answer 20

Clonal selection by dendritic cells survey for T cell with complementary TCR, Once selected this undergoes clonal expansion and differentiates from naive T cells into memory cells which can reside in lymphoid tissue and increase response following immunisation or effector cells which have functions depending on their differenitation. Memory cells can become effector cells and vice versa. Eventually they die.

Question 21

How are T cells cleared?

Answer 21

Tregs which release granzymes.

Question 22

How does memory affect clonal expansion?

Answer 22

Increases the rate of clonal expansion.

Question 23

How do CD4+ Tfh cells form?

Answer 23

They form from clonal selection via dendritic cells. It begins as a pre-cell which enters the germinal centre to become a mature CD4+ Tfh cell.

Question 24

What immunity is Th1 involved in?

Answer 24

Type 1 in response to microbial damage

Question 25

What immunity is Th2 involved in?

Answer 25

Type 2 immunity in response to helminths

Question 26

How do T regs inhibit the immune response?

Answer 26

They take up cytokines such as IL-2 for T cell differentiation which leads to apoptosis
-> release granzymes and perforins and can suppress T cells by releasing IL-10, IL-35 and TGF-Beta
They can use MHC Class receptors to bind to antigen receptor cells and suppress the TCR of a T cell.

Question 27

How can Th17 inhibitors be used for?

Answer 27

Treats autoimmune disease and inflammation

Question 28

What are senescent T cells?

Answer 28

T cells that have undergone extensive cell replication that it has irreversible cell cycle arrest with telomere shortening.

Question 29

What are anergic T cells?

Answer 29

T cells which receive suboptimal signals for differentiation.

Question 30

What are exhausted T cells?

Answer 30

T cells which receive overstimulation of signals that leads to loss of effector function which reduces the immune response.

Question 31

What is calcineurine?

Answer 31

A phosphatase enzyme calcineurine for calcium-dependent activation of transcription of TCR receptors for T cell activation