Effector T Lymphocytes

Question 1

How does cell mediated immunity better protect us from IC pathogens?

Answer 1

better digestion by activating macrophages and inflammation

better killing by lysing infected cells

Question 2

How is a T lymphocyte response induced?

Answer 2

dendritic cells in tissues acquire antigens and more to lymph nodes
activated my PAMPs
mature and present antigen on MHC which is detected by TCR
T cell matures to Te cells

Question 3

Summarise the MHC-TCR interaction

Answer 3

IC pathogens processed in cytosol and presented on MHCI to CD8 T cells
EC pathogens processed in endoscopes and presented on MHCII to CD4 T cells

Question 4

Why are T cells recirculated?

Answer 4

increase chance on encountering antigen

Question 5

Summarise the induction phase of cell mediated immunity

Answer 5

dendritic cell infected and acquires material
moves to lymph nodes and hydrolyses material to peptides which presents on MHCII
circulating T cell enters lymph and encounters complex and matures to Te cell
Te cell releases chemokine and moves back to site of infection

Question 6

Summarise the effector phase of cell mediated immunity

Answer 6

Te sees MHC peptide complex on infected cells and performs function

Question 7

Summarise the memory phase of cell mediated immunity

Answer 7

Te pool contracts to memory

Question 8

What are the 3 signals required for a response?

Answer 8

antigen recognition
co-stimualtion
cytokine release

Question 9

What are the effector functions of Tc cells?

Answer 9

destroy target cells such as virus or tumour infected by recognising MHCI peptide 
release granules to induce apoptosis 
fragmentation of nuclear DNA
perforin, granzymes, granulysin
kill multiple cells

Question 10

What are the effector functions of Th cells?

Answer 10

macrophage activation
delayed type hypersensitivity
B cell activation
regulation
differentiate into subsets

Question 11

What are the subsets of Th cells and their function?

Answer 11

Th1 - produce interferon
Th2 - produce IL-4, 5, 13, anti-multicellular
TfH - produce IL-21, generates isotype switched antibodies
Th17 - secrete IL-17 autoimmune
Treg - regulate activity of other T cells and maintain tolerance of self antigens

Question 12

Summarise macrophage activation

Answer 12

Th1 cells activate macrophages to promote IC pathogen killing
activated macrophages express increased levels of CD40 and TNF-alpha receptors
secrete TNF-alpha which synergises with IFN-gamma in induction of antimicrobial effector mechanism

Question 13

Summarise delayed type hypersensitivity

Answer 13

protective or pathological

defence against IC pathogens

Question 14

How can DTH become pathological?

Answer 14

if the antigen source isn’t eradicated then chronic stimulation and granuloma formation
if antigen isn’t a microbe e.g.g pollen then a tissue injury without protection produced

Question 15

Summarise the DTH response

Answer 15

2 phase

• dendritic cells take up antigen and present to T cell
• Te cell pool reacts quicker second time

Question 16

How do memory T cells differ from naive T cells?

Answer 16

less stringent activation
proliferate faster
express different chemokine receptor

Question 17

How do T cells differ from B cell maturation?

Answer 17

no isotype switching or affinity maturation

Question 18

Why is T cell exhaustion important?

Answer 18

if antigen source isn’t cleared then T cell would kept proliferating which is dangerous to body so exhaust and shut down for protection

Question 19

What are negative effects of Te cells?

Answer 19

autoimmunity

transplant rejection

Question 20

How may a memory response be bad?

Answer 20

excess response than is required to clear pathogen
response in wrong anatomical area
targets against self
targets against benign antigens