Adaptive Immune System- T-Cells

Question 1

The adaptive immune system comprises

Answer 1

Humoral immune response

Cellular immune response

Question 2

Humoral immune response

Answer 2

EC pathogens 
Blocks the virus binding to receptors
Neutralises the toxins 
Opsonization of pathogens 
Activates complement 
NO DIRECT KILLING

Question 3

Cellular immune response

Answer 3

IC pathogens
Induces apoptosis in the infected cells
Activates macrophages– phagocytosis
Activation of B-cells– ab prod

Question 4

T-Cells and their relationship with the Thymus

Answer 4

Nurse cells in particular help to build receptors on immature (make them either CD4 or CD8, they are double negative at this stage)
They start with nothing, then both CD4 and CD8, then MHC selects whether it is CD4 or CD8

Question 5

3 important cells in the medulla of the thymus

Answer 5

Medullary epith
Interdigitating dendritic cell
Hassall’s corpuscles- regulatory function

Question 6

2 Types of T-cells in the thymus

Answer 6

Cortical thymic epithelial cells (cTEC)

Medullar thymic epithelial cells (mTEC)

Question 7

Positive selection

Answer 7

Good T-Cells can recognise MHCI or MHCII

Question 8

Medullar Thymic epithelial cells mTEC

Answer 8

Contain AIRE gene- Autoimmune Regulator Gene
-own antigen and own peptides
-present own proteins on MHCI and MHCII
Important so that the fetus can produce proteins important in fetal life

Question 9

Selection of alphabeta T-Cells

negative selection

Answer 9

The organism needs:

• those that can recognise own MHC
• those with no recognition of own epitop

The organism destroys:

• not useful: where there is no recognition of own MHC
• danger, where there is recognition of own peptides (own epitops) i.e recognises self as foreign?

Question 10

Affinity

Answer 10

Strength of interation btw epitop and paratop i.e btw T-cell receptor and MHC

Question 11

Avidity

Answer 11

All affinity

if this is big, the affinity is strong

Question 12

Nature, Naive T-Lymphocytes

Answer 12

Less than 5% of initial cells
Have not connected with peptides (except natural regulator T-Cells)
Go to secondary lymphoid tissues
Wait for dendritic (APC) cells in the paracortical part of lymph nodes

Question 13

Activated DC meets naive lymphocytes

Answer 13

DC in the tissues meets pathogen, inflammation causes it to become activated (contains macropinosome) then this travels via afferent lymph duct to the lymph node- it encounters the T-cell in the deep cortex/paracortical zone

Question 14

MHC restriction

Answer 14

The CD8 T-Cell needs to recognise the MHC complex on the dendritic cell

Question 15

Co-receptors of T-Cells

Answer 15

CD8 binds to the beta2 part of MHCI
(e.g of T-cell in this case would be cytotoxic)

CD4 binds to the second domain of MHCII beta chain
(e.g of T-Cell in this case would be T helper)

Question 16

Costimulation

Answer 16

Cytokines are released by T-helper cells and APC’s

Question 17

Plasmocytoid Dendritic Cell (pDC)

Answer 17

Activated by viral infection- produces IFN alpha and beta
Firstly immature DC with PRR in the periphery
Migrates to lymph nodes where it matures:
-enhancement of MHCII, CD40 and other costimulators
-enhancement of migration ability
Activation of T-helper through IL-12, which is produced in the lymph nodes

Question 18

Tasks of cytotoxic T-Cells

Answer 18

Killing based on the Atg presented through MHCI

CK’s are needed

Question 19

Tasks of T-Cells

Answer 19

Use the CK’s produced by dendritic cells to control immune processes

Question 20

alphabeta CD4+ Effector T-Cells

Answer 20

Th1
Th2
Th9 
Th17**
Th22
Tfh

Question 21

Th1

Answer 21

IFN gamma
TNF alpha
IL-2

Activation of macrophages

Question 22

Th2

Answer 22

IL-4,5,13

Humoral response

Question 23

Th9

Answer 23

IL-9, 10

Parasitosis
Chronic allergy

Question 24

Th17 NB!!

Answer 24

IL-17A
IL-17F
IL-26
IL-22

Activation of PMN in chronic inflamm

Question 25

Th22

Answer 25

IL-22

Chronic dermatitis

Question 26

Tfh

Answer 26

IL-21

Costimulation of B-Cells in folliculi

Question 27

Cellular immune response

Answer 27

Activation phase:
-viral proteins bound to MHCI
-these are recognised by the TCR on Tc
-all mediated by IL-2
Then replication and clonal expansion of Tcs 

Effector phase:

• TCR recognises the antigen bound to MHCI again on another infected cell
• Tc emits perforin and granzyme

Apoptosis induction in infected cells before viral replication
T-cells also die, but the memory cells remain

Question 28

Tasks of Tcs in Viral infectins

Answer 28

Damage the viral genome by enzymes activated during cytolysis
IFNgamma has antiviral activity, which is strengthened by TNF
-activates macrophages
-Ig isotype change- complement activation and Ab prod- opsonisation of viral particles- removal by phagocytosis