Immunology Lecture 14 - B Cell Stuff

clonal selection hypothesis

B cells create clones of the same antigen receptor

what does every heavy chain locus have?

spare exons

what does activation-induced deaminase (AID) do in B cells?

breaks intervening DNA for antibody production

when does AID do this?

when CD40 (B cell) binds to CD40L (T cell)

how does cytokines affect B cell class switching?

tell B cell what to become

what does alternative splicing allow?

allows the plasma cell to have IgG on the surface while secreting IgG

what happens to self-reactive B cells that escape central tolerance?

removed through peripheral tolerance

true or false: self-reactive B cells that escape the central and peripheral tolerance can cause autoimmune diseases

true

what are the possible fates of B cells during negative selection?

1. apoptosis

2. anergy

3. receptor editing

what is receptor editing?

rearrangement of other light chain alleles

what happens if the rearrangement is successful?

B cells leave the bone marrow and go to spleen

true or false: 90% of B cells do not make it out of the bone marrow

true

what happens when the B cells go to the spleen?

undergo more negative selection

negative selection

faced with self antigens that they had not seen in the bone marrow

what happens to B cells if they survive the negative selection in the spleen?

express a lot more IgD and go into the splenic follicles

what happens to B cells when they are in the splenic follicles?

upregulate BAFFR

BAFFR

pro-survival receptors in B cells

what happens if the B cell does not upregulate BAFFR?

undergoes apoptosis

BAFFR deficiency characteristics

1. few circulating B cells

2. low IgM and IgG

3. normal/high IgA

what is autoimmune diseases linked to?

overexpression of BAFF

what are B cells in the secondary lymphoid organs called?

follicular B cells (B2 B cells)

what defines a follicular B cell?

IgM and IgD on the surface

what happens if a cognate antigen is encountered?

the cell becomes a plasma cell or memory cell

what does a plasma cell do?

produces antibodies

what does a memory cell do?

recirculates

what cells are an innate lymphocyte subset?

B1 B cells

where are B1 B cells located?

peritoneal and pleural cavities

what do B1 B cells mainly produce?

IgM

what do B1 B cells mainly recognize?

microbial carbohydrate epitopes

where are B1 B cells produced?

fetal liver

what is a difference between B1 and B2 cells?

B2 have high levels of CD21

what enhances the signal strength for B cells during activation?

C3d and CD21

what creates C3d?

C3b

B cells also express _____s

TLRs

what happens when a TLR is bound to a PAMP?

the B cell is activated at a lower threshold of an antigen

what causes B cells to clonally proliferate?

when a B cell recognizes its antigen

what happens if the T cell produces IL-4 and IL-5?

the B cell switches to IgE

what happens if the T cell produces IFN-gamma?

the B cell switches to IgG

what makes follicular dendritic cells different?

help with antibody affinity maturation

what do follicular dendritic cells produce?

1. IL-6

2. IL-15

3. BAFF

germinal center reaction

1. affinity maturation

2. class switching

3. produce plasma cells that have high affinity antibodies

4. formation of membory B cells

3 zones of the germinal center reaction

1. dark zone

2. light zone

3. mantle zone

dark zone

proliferating cells undergo hypermutation

light zone

cells that have low affinity or are self-reactive undergo apoptosis

mantle zone

B cells become antibody secreting plasma cells OR memory B cells

what are memory B cells important for?

secondary response