B Lymphocyte Differentiation Flashcards
where do the precursors for all species’ B lymphocytes form?
in the bone marrow
where do B cells develop in birds?
Bursa of Fabricius
where do B cells develop in everyone BUT birds?
bone marrow
when does the bursa of fabricius begin to regress and what does this mean?
around 6 months of age, cannot regenerate B cells after that point
what specifically in the bone marrow causes development of B cells?
specific microenvironments
what are the 6 stages of B cell development?
- Pre-Pro B cells
- Pro B cells
- Pre B cells
- Immature B cells
- Transitional cells
- B cell survival
what happens in the first stage, Pre-Pro B cell of B cell development?
preparation for recombination
what happens in the second stage, Pro B cells, of B cell development? how many stages within this stage? list and describe the 2
complete recombination of heavy chain, 2 stages
- early stage: D to J recombination of heavy chain
- late stage: V to DJ recombination of heavy chain
what does successful recombination of the heavy chain in the Pro B cell stage of B cell development trigger?
committment to B cell lineage
what happens in the third, Pre B cell, stage of B cell development? (3)
- Pre B cells express mu heavy chain BCR on cell surface
- cell proliferates
- after proliferation, light chain recombination occurs
what does recombination of the light chain of the BCR in the third, Pre B cell, stage fo development yield?
a complete BCR
what happens in the fourth, Immature B cell, stage of B cell development? (2)
- IgM is expressed on cell surface
2. negative selection
describe negative selection during the fourth, Immature B cell, stage of B cell development
select against cells that recognize self-antigen
what happens to the cells that recognize self antigen in the immature B cell stage of B cell development? (2)
- undergo apoptosis
2. receptor editing
what is receptor editing?
different V and J genes on the light chain of the BCR are selected to try to make a B cell that does not recognize self-antigen
what happens to B cells after they undergo receptor editing?
they move on to the next stage of B cell development even if they are unsuccessful in making a B cell that does not recognize self-antigen, there is no second selection process
what happens in the fifth, Transitional B cells, stage of B cell development? and where does it occur? how many stages? list and describe
occurs in the spleen; 2 stages
T1: negative selection occurs again to ensure that cells that underwent receptor editing are not self-reactive and apoptosis occurs if they are, cells that survive express receptor for B cell activation factor (BAFF), cells express IgD and IgM
T2: expression of IgD, IgM, and BAFF receptor allow for cells to become mature B cells
what is BAFF?
a survival signal for B cell development
what happens in the sixth and final stage of B cell development?
mature B cells leave the spleen and circulate through the body
