Lecture 3: Antigen Receptors and MHC Flashcards
Are B cell receptors membrane bound IgE?
No
Are B cell receptors membrane bound IgG?
Yes
What are heavy and light chains joined by in BCR?
Disulphide bridges
How is diversity of BCR achieved?
Recombination
What are the parts to the Ig light chain in the BCR?
Variable (V)
Joining (J)
Constant (C)
What are the parts to the Ig heavy chain in the BCR?
Variable (V)
Joining (J)
Constant (C)
Diversity (D)
How many combinations roughly are there of light and heavy BCR combinations are there in the BCR?
2 million
In which order are the light chains in BCR recombinated?
V to J at the DNA level and then the C at level of transcription
In which order are the heavy chain in the BCR recombined?
D to J then V then C at level of transcription
Which enzymes catalyse the V(D)J recombination in BCR?
RAG1 and RAG 2
What does the addition and removal of nucleotides do in the recombination mechanism in BCR?
Increases the diversity of the repertoire
How is it ensure that a B cell does not express more than one receptor?
Allelic exclusion
What is allelic exclusion?
If a productive gene rearrangement occurs in one copy of the chromosome (allele) the expression from the other is silenced
Explain the process of allelic exclusion in BCR?
Step 1: D to J on heavy chain
If successful
Step 2: Attempt to attach V to this heavy region
If unsuccessful
Step 3: Will try to attach the other alley of V
If successful
Step 4: Becomes a Pre-BCR and puts a heavy chain on the surface with a surrogate light chain
Step 5: The B cell gets a signal to attempt to recombine its own light chains. We have two types of light chain Kapa and lambda
Step 6: Light chain attempts to rearrange its kapa gene
If unsuccessful
Step 7: Rearrange the second kapa gene
If unsuccessful
Step 8: Rearrange the lambda gene
If unsuccessful
Step 9: Rearrange the second lambda gene
If unsuccessful
Step 10: Cell death
Each stage it has a second go at rearranging its other allele
Does the BCR signal directly?
No
