Lecture 5- Adaptive immunity 2- Part 2 Flashcards
When does the somatic hyper-mutation take place?
-Following B cell recognition of an antigen
At which stage of the B cell does the mutations take place?
-Centroblast stage
Where does the mutation take place?
-Germinal centres
What is the overall goal of Somatic Hypermutation?
-High affinity antibodies
Does the mutation distinguish between favourable and unfavourable mutations?
No- Result:
- higher affinity for antigen
- Lower affinity for antigen
- No change in affinity
SO how does the antibodies with high affinity selected? (affinity maturation)
- SELECTION process for antigen binding: occurs at the light zone of germinal centre
- B cell that produce the highest affinity antibodies are selected
What is the purpose of somatic hypermutation?
- Diversity generating process
- Adds further diversity to already rearranged (V(D)J recombined) segments through the introduction of POINT MUTATION
What is the rate of the mutation via Somatic Hypermutation?
1-base per 1000~1 million times higher mutation rate than observed during normal division
Why is it called hypermutation?
Massive increase in the incidence of MUTATION
why do these mutation not cause any problems?
-Occur at RESTRICTED LOCI:- known as the HYPERVARIABLE region
what is the site called that is involved antigen recognition on the antibody?
-Complementarity determining regions (CDR)
what is the most type of mutation?
nucelotide substitution
What are the two enzymes that guide the process of Somatic hypermutation?
1) Activation-induce cytidine deaminse (AID)
2) Uracil N-glycosylase:
removes uracil bases generated by AID mediated deamination
which enzyme triggers Somatic hypermutation?
- Activation-induce cytidine deaminase (AID)
what does the AID do?
-AID deaminates cytidine to uracil - this base mismatch
