B Cell Development, Activation, and Differentiation

Question 1

where are B cells made? (3) where do they mature?

Answer 1

B cells originate in the fetal liver, spleen, and bone marrow/bursa; mature in bone marrow?

Question 2

what stimuli are required to cause B cell maturation?

Answer 2

the bone marrow stroma signals a pre-B cell to rearrange heavy and light chains and begin maturation

Question 3

what events cause a B cell to undergo apoptosis? (4)

Answer 3

1. when random D and J segments join with a random V segment, if a B cell does not express a functional H chain, it gets a second chance, but if after that 2nd chance the H chain still no function = apoptosis
2. after H chain, L-chain rearrangement occurs; if not function 1st time, second chance, but if not functional second time = apoptosis
3. when H and L chain associate, they try to form a BCR; but if no BCR formed = apoptosis
4. or if they form a self-reactive BCR, second chance and then if still self-reactive = apoptosis

Question 4

what product do mature B cells produce?

Answer 4

antibodies

Question 5

know the basic structure of immunoglobulins

Answer 5

2 main regions
Fab region: antigen binding site that binds only a specific epitope; is HIGHLY VARIABLE and made up of the light chain
Fc region: determines the class of antibody, and therefore its effector response; is a constant region and made up of the heavy chain

Question 6

name the different classes of antibodies (5)

Answer 6

1. IgG
2. IgM
3. IgA
4. IgD
5. IgE

Question 7

identify basic differences in structure for each antibody class

Answer 7

monomers: IgG, IgE, IgD
dimer: IgA
pentamer: IgM
(dimers and pentamers joined by a joining chain that is different than the J of V-J recombo!!)

Question 8

know the signals required for activated B cells to make antibody (3)

Answer 8

1. stimulation by antigen without T cells via simultaneous activation of BCR and co-receptor (BCR recognizes something on a bacterial cell wall and is activated)
2. stimulation by antigen without T cell via strong cross-linking of BCR via a repetitive protein epitope
3. stimulation by T cell; requires an activated T cell

Question 9

compare and contrast activation of a B cell independent of T cell and by T cells

Answer 9

if activated without T cell help, there is a weaker signal, no class switching, and no increase of B cell affinity for antigen (half-assed response); but if stimulated by T cell; leads to clonal expansion of B-cells, production of plasma cells, AND production of memory B cells (a full, much stronger response)

Question 10

understand the clinical consequence of class-switching

Answer 10

once class-switching occurs there is no going back (develop this more)

Question 11

know the order in which antibody classes are produces and why this matters

Answer 11

a naive B cell will express membrane bound IgM and IgD; after exposure to antigen we get memory B cells and IgG is predominant; can help figure out where an animal is in its exposure to a pathogen/vaccine response

Question 12

know the anatomical location in which antibody classes predominate (serum, mucosa)

Answer 12

IgA: secreted at mucosal surfaces like resp tract, GI tract, urinary tract, skin, mammary glands, and eyes
IgG: main antibody in serum and the makes up the majority of antibodies produces
IgM: predominates in blood
IgD: primarily on naive B cells as a receptor for antigen (fact-check)
IgE: in tissues and on mast cells and basophils

Question 13

know the main functions of antibodies (see immunology class brainscape)

Answer 13

IgA:
IgE: eosinophil and mast cell degranulation
IgD:
IgG:
IgM: