B Lymphocyte Differentiation

Question 1

where do the precursors for all species’ B lymphocytes form?

Answer 1

in the bone marrow

Question 2

where do B cells develop in birds?

Answer 2

Bursa of Fabricius

Question 3

where do B cells develop in everyone BUT birds?

Answer 3

bone marrow

Question 4

when does the bursa of fabricius begin to regress and what does this mean?

Answer 4

around 6 months of age, cannot regenerate B cells after that point

Question 5

what specifically in the bone marrow causes development of B cells?

Answer 5

specific microenvironments

Question 6

what are the 6 stages of B cell development?

Answer 6

1. Pre-Pro B cells
2. Pro B cells
3. Pre B cells
4. Immature B cells
5. Transitional cells
6. B cell survival

Question 7

what happens in the first stage, Pre-Pro B cell of B cell development?

Answer 7

preparation for recombination

Question 8

what happens in the second stage, Pro B cells, of B cell development? how many stages within this stage? list and describe the 2

Answer 8

complete recombination of heavy chain, 2 stages

1. early stage: D to J recombination of heavy chain
2. late stage: V to DJ recombination of heavy chain

Question 9

what does successful recombination of the heavy chain in the Pro B cell stage of B cell development trigger?

Answer 9

committment to B cell lineage

Question 10

what happens in the third, Pre B cell, stage of B cell development? (3)

Answer 10

1. Pre B cells express mu heavy chain BCR on cell surface
2. cell proliferates
3. after proliferation, light chain recombination occurs

Question 11

what does recombination of the light chain of the BCR in the third, Pre B cell, stage fo development yield?

Answer 11

a complete BCR

Question 12

what happens in the fourth, Immature B cell, stage of B cell development? (2)

Answer 12

1. IgM is expressed on cell surface

2. negative selection

Question 13

describe negative selection during the fourth, Immature B cell, stage of B cell development

Answer 13

select against cells that recognize self-antigen

Question 14

what happens to the cells that recognize self antigen in the immature B cell stage of B cell development? (2)

Answer 14

1. undergo apoptosis

2. receptor editing

Question 15

what is receptor editing?

Answer 15

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

Question 16

what happens to B cells after they undergo receptor editing?

Answer 16

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

Question 17

what happens in the fifth, Transitional B cells, stage of B cell development? and where does it occur? how many stages? list and describe

Answer 17

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

Question 18

what is BAFF?

Answer 18

a survival signal for B cell development

Question 19

what happens in the sixth and final stage of B cell development?

Answer 19

mature B cells leave the spleen and circulate through the body