A?4. T cell recognition

Question 1

T cell life

Answer 1

1. Selected in thymus
2. Matures & migrates into periphery
3. circulates through lymph nodes
4. If recognizes antigen: activates effector function

Question 2

TCR

Answer 2

2 protein chains paired: a/B
variable region: recognises diversity
transmembrane w/ cytoplasmic tail: signalling upon recognition

Question 3

how do TCR become diverse

Answer 3

due to random recombination & mutation of germline DNA

recombination shuffles genes

Question 4

Selection of T cells

Answer 4

selected in thymus. Too strong affinity = recognition of self: clonal deletion

Question 5

T cell recognises

Answer 5

Short peptides generated from PAP
short peptide = antigen (9-11a.a)
Lysosome: chops protein to peptides

Question 6

Steps of antigen taken up to presentation to MHC

Answer 6

1. antigen taken up from extracellular space into intracellular vesicles
2. early endosomes of neutral pH - endosomal proteases are inactive
3. acidification of vesicels activates proteases to degrade antigen into peptide fragments
4. Vesicles containing peptides fuse w/ vesicles containing MHC-II

Question 7

If T cell recognises antigen/ MHC

Answer 7

Naïve antigen-specific T cells recirculate looking for phagocytes presenting their cognate antigen
Upon recognition T cell & antigen presenting cell form interaction
TCR transmits signal & T cell becomes activated

Question 8

Adaptive advantages

Answer 8

allows lymphocyte pop to recognise antigen peptides from many potential pathogen
Stops pathogens evading immune system

Question 9

Adaptive Disadvantages

Answer 9

can react to non harmful pathogens: allergies/ autoimmunity

-> require cross talk: danger signals = alarm signals from injured cells