13- B Cells

Question 1

How is antigen recognition and response of B cells different from T cells?

Answer 1

Antigen does not need to be presented to B cells by APCs, they can recognize antigens that are free and not bound- the B cell recognizes “native” epitopes (basically unprocessed antigen)

Question 2

Discuss the role of TH cells in the activation of B cells.

Answer 2

-TH cell contact with a B cell is very important. The TH cell gets presented with the same antigen (by APC) that the B cell gets presented with, so the TH cell then knows the type of reaction needed or type of cytokines needed to destroy the pathogen

Question 3

Explain why dendritic cells are important in the primary B cell response

Answer 3

After B cells are activated, they migrate into germinal centers. There will be multiple B cells with varying affinities for an antigen. B cells with high affinity membrane immunoglobulins bind to the antigen on follicular DCs and present antigen to T helper cells. The B cells that recognize antigen on FDC’s are selected to survive; other B cells die

Question 4

Describe antibody class switching

Answer 4

B cells will initially produce large amounts of IgM in response to an invader. In order for different immunoglobulins to be created, a B cell needs TH cells and the specific cytokines they release will then decide the class of Ig that gets released

Question 5

Describe affinity maturation

Answer 5

When antibodies gain higher affinity for an antigen. Only the B cells producing the antibodies with the highest affinity will survive

Question 6

Compare and contrast the primary and secondary immune responses in regard to lag time, titer, antibody class, and antibody affinity

Answer 6

Primary response
- Lag time: 5-10 days
- peak response: smaller
- Antibody type: IgM dominant
- Antibody affinity: lower average affinity, more variable

Secondary Response:
- Lag time: 1-3 days
- peak response: larger
- antibody type: increase in IgG dominance
- Antibody affinity: higher average affinity (affinity maturation)

Question 7

Describe a T-independent B cell response

Answer 7

T-independent antigens bind directly to B cell TLRs and cross link several BCRs, providing a sufficient signal for B cell proliferation. These antigens only trigger IgM responses with low affinity antibodies , short lived plasma cells, and fail to generate memory cells. This is because they don’t induce T cell co-stimulation and this cannot trigger the class switch

Question 8

Describe a T-dependent B cell response

Answer 8

T-dependent antigens can stimulate B cells to become activated but require cytokine assistance delivered by TH cells. The TH cell interacting with the B cell with the proliferation and differentiation into isotype-switched, high-affinity antibodies, memory B cells and long-lived plasma cells

Question 9

When BCRs are shed into body fluids, they are called _______ or _________.

Answer 9

immunoglobulins or antibodies

Question 10

BCRs consist of two _______ and two ______ chains bound together by _______ bonds.

Answer 10

Heavy
Light
Disulfide

Question 11

T cells stimulate B cells through co-stimulatory molecules, _________ ________, and __________.

Answer 11

Interactive receptors
Cytokines

Question 12

Activated B cells become either antibody production _______ _______ or _______ ________

Answer 12

Plasma cells
Memory cells

Question 13

The differentiation of B cells into plasma cells takes place in the _______ _______ of lymph nodes and other secondary __________ organs.

Answer 13

Germinal centers
Lymphoid