IAH5 - Adaptive immunity 1

Question 1

What 3 signals activate T cells?

Answer 1

Recognition of antigen
Co-stimulation
Cytokines

Question 2

Name the highly variable antigen receptors recognising structures that are specific to individual pathogens on T and B cells

Answer 2

T cell receptor (TCR)

B cell receptor (BCR)

Question 3

How are antigens presented by APC?

Answer 3

MHC

Question 4

What is the purpose of specific antigen receptors?

Answer 4

Adaptive immunity with greater sensitivity and specificity

Question 5

What make MHC difficult for pathogens to evade immune response?

Answer 5

Polygenic (contains many MHC genes - so every individual has different peptide binding specificities
Polymorphic - multiple variants of each gene within population

Question 6

MHC class I

a) presents to…
b) expressed on …

Answer 6

a) CD8 (cytotoxic T cells)

b) Most nucleated cells

Question 7

MHC class II

a) presents to…
b) expressed on …

Answer 7

a) CD4
b) APC and cells in the thymus
DC, macro, B, fibroblasts, epithelium

Question 8

Which MHC is associated with beta 2 microblobulin?

Answer 8

Class I

Question 9

Describe endogenous pathway?

Answer 9

Assembly of MHC class I antigen complex

Antigen broken down by proteasome in cytoplasm 
Peptide to ER where they bond MHC class I, packaged and modified in Golgi, displayed on cell membrane and binds CD8

Question 10

Describe exogenous pathway?

Answer 10

Assembly of MHC class I antigen complexes

pathogen taken up by phagocytosis, proteolysis breaks down e.g. lysozyme, MHC class II fuses with antigen containing vesicle, displayed on surface and binds Cd4

Question 11

How and where are TCRs made?

Answer 11

Thymus

Random somatic DNA recombination (RAG enzyme)

Question 12

What is positive selection?

Answer 12

T cell selected when it can recognise MHC (it is MHC restricted)