B cell development 2 Flashcards
When are the RAG proteins first expressed during B cell development, and what is occuring at this time?
At the pro-b stage, when the heavy chain loci are rearranging
Why is there a gap in the expression of the RAG proteins?
It is in the proliferative stage, when no rearrangements are occuring
What are the two times the RAG proteins are expressed?
When the heavy and light chain loci are rearranging
When is TDT highly expressed?
When the heavy chain loci are being rearranged
When is N nucleotides more common, VDJ recombination or VJ recombination?
VDJ
Why is CDR3 the most variable part of the antibody?
It is part of the heavy chain, which has N nucleotides
What proportion of immature B-cells have affinity for self antigens
70-75%
What happens to B cells that react with a self antigen in the bone marrow?
It is kept in the bone marrow
What happens to the B cell that is kept in the bone marrow?
The B cell can re-rearrange its light chain loci
What is receptor editing?
A B cell re-rearranging its light chain loci
When are B cells that have undergone receptor editing allowed to leave the bone marrow?
When they rearrange their light chain loci so they dont recognise self antigens
What do immature B cells express once they leave the bone marrow?
IgM and IgD
Conditions for B cells to become activated?
Bind to antigen in the right conditions (2nd lymphoid tissues)
Internalise the antigen
Present the antigen to t cells that recognise that antigen
How many cells per day start the process of B cell development?
2.5 billionq
How many immature B cells leave the bone marrow?
30 billion
What do immature B cells compete with for access to 2ndary lymphoid tissue?
Mature B cells that have previously hd survival signals
Half life of immature b cells w/o 2ndary lymphoid tissue access?
2 days
How long to B cells with survival signals last?
100 days in circulation
How do mature b cells gain access to follicles more easily?
They have the correct receptors to guide them to the 2ndary lymphoid tissues
What are naive b cells?
B cells that have not been activated by an antigen, and so not been activated by an antigen
What happens if the immature B cells get into the secondary lymphoid tissues?
They receive survival signals and will leave the 2ndary lymphoid issues via lymphatic vessels
What are mature B cells looking for in 2ndary lymphoid tissues looking for?
Antigen
What happens to the majority of mature b cells that eter the 2ndary lymphois tissue?
They dont find an antigen, and end up leaving
What happens to mature b cells that find antigens in the 2ndary lymphoid tissue?
They bind to the antigen, internalise it, endocytose it
What is receptor mediated endocytosis?
A b cell binds to an antigen and takes it up via endocytosis
What happens to an antigen once a B cell takes it up?
It is processed into short peptides
What are the processed peptides of an antigen loaded onto in a B cell?
MHCII proteins
What do the MHCII proteins do once they have the short antigenic peptides on them?
They move to the surface of the B cell and present them
What is a cognate interaciton?
An interaction between a b cell and a t cell where t cells recognise an antigen on a B cell, and the t cells send a signal
What does a b cell do after a t cell recognises the antigen it presents?
Proliferate to become plasma cells and memory b cell
