Lecture 5 - B cell Development Flashcards
True or false - the antigen binding site of an antibody occurs at the C-terminus.
False - occurs at the N-terminus. The C-terminus is the Fc region.
How many different light chain constant domains are there, and what are they?
Two - lambda and kappa
How many different heavy chain constant domains are there, and what are they called?
Five (major ones) - alpha, mu, gamma, delta and epsilon.
Name the process that allows such vast diversity of B cell paratopes.
Somatic gene rearrangement
How many different possible kappa segments are there? What level does Variable kappa and joining segment recombination occur at?
About 85
The level of the DNA
What level does the combination of the VJ segment with the Constant kappa segment occur at?
RNA (during splicing)
How many Variable, Diversity and Joining segments are there for the heavy chain of antibodies? At what level are these recombined?
V = 134 D = 13 J = 4
Level of the DNA
At what level is the newly re-arranged heavy chain VDJ segment combined with a mu or delta constant domain?
The RNA - during splicing
What mechanism prevents B cells producing two different antibodies?
Allelic exclusion - only one chromosome is subject to re-arrangment
Which B cell receptor chain - heavy or light - is rearranged first? What is the B cell called after that?
Heavy
Pre B cell
Once both chains of the B cell receptor have been re-arranged, what is the B cell known as? What process still has to occur before the cell is ‘mature’?
Immature B cell
Differential RNA splicing > IgM or IgD producing
Regarding B cells;
Blast cells may differentiate into what?
Plasma cell or memory B cell
How do B cells make both soluble and membrane-bound antibody?
Use of a different polyadenylation site to make a different mRNA for that antibody, which has 20 hydrophilic aa’s at the C-terminus, rather than the ~40 hydrophobic aa’s.
How is a B cell able to produce both IgM and IgD at once?
Splice the RNA for the antibody molecule differently, as IgD constant region is just downstream of the IgM
What level (DNA or RNA) does class switching from IgD to any other class occur at?
DNA
