B cell differentiation
rearrangement of D-J of heavy chain
rearrangement of V-DJ of heavy chain
large Pre-B cell
small amts of expression of heavy chain on outside of receptor; expression signals termination of heavy chain gene rearrangement
Surrogate L chain
made of VpreB and lambda 5 proteins; act as "L" chain so heavy chain can be expressed on outside of B cell in Pre-B cell stage
its presence signals to stop H rearrangement and start L rearrangement
mu Heavy chain
its expression stimulates L chain rearrangement
L chain rearrangement inhibitor
causes VpreB and lambda 5 to be displaced and allows L and H chain to come together
How does RAG play a role in B cell dev?
it can phosphorylate to cause cessation of H chain gene rearrangement in pre-B cell stage
turned on for L chain rearrangement
When do L chains stop rearranging?
one IgM is expressed on the surface of immature B cells
What are three fates of immature B cells in bone marrow?
1. strong signal binding with self-antigen=clonal deletion and apoptosis
2. signal binding w/ sol self-antigen=immature B cell migrates to periphery and becomes inactive to Ag and eventually dies
3. no signal binding w/ self-antigen=migrates to periphery and becomes mature B cell (expresses IgD and IgM)
transitional B cells
immature B cells that leave bone marrow and enter periphery; can mature into 3 types of B cells:
1. B-1 B cells
2. marginal zone B cells
3. follicular B cells
B-1 B cells
forms from transitional B cells; resides in pleural and peritoneal cavities and make natural Ab to function in innate immune response; esp useful against bacteria
Marginal zone B cells
live in marginal zone of spleen and make T-indep and T-dep Ab responses to bloodborne Ag
Follicular B cells
recirculate btw blood and lymphoid follicles and make T-cell dep and participate in germinal center rxn
What are some characteristics of plasma cells?
no surface Ig
no MHC-2 expression
make secreted form of Ig
are not inducible (growth)
end stage of B cell differentiation
What are some characteristics of a resting B cell?
expresses surface Ig
expresses surface MHC-2
does not secrete Ig
is inducible (growth)
What are some characteristics of memory B cells?
can revert back to resting B cell stage
can express any Ig class
go to live in bone marrow and can stay for yrs
B cell differentiation
MS1/Mod 1: immunology; B cell differentiation