Lecture 12 - Part I

Question 0

What initiates the immune response for B lymphocytes?

Answer 0

Recognition of Ags by specific BCR on the B lymphocyte

Question 1

As part of the humoral immune response, what do the progeny of the B cell clones differentiate to into?

Answer 1

1. Plasma cells –> IgM
2. Other Ig isotypes
3. Affinity maturation
4. Memory cells

Question 2

Antigen binds to which membrane Ig isotype on mature, naive B cells? What does this binding cause?

Answer 2

Ag binds to IgM and IgD; activates these cells

Question 3

What are the steps of B cell activation?

Answer 3

proliferation –> clonal expansion –> differentiation –> generation of Ab secreting plasma cells and memory B cells

Question 4

One B cell could give rise to how many Ab secreting cells per week?

Answer 4

5000

Question 5

What is heavy chain isotype switching?

Answer 5

when some activated B cells begin to produce Abs other than IgM and IgD

Question 6

As humoral immune response develops, activated B cells produce Abs that bind to Ags with increasing affinity, progressively dominating the response, what is this called?

Answer 6

Affinity Maturation

Question 7

What type of response is Ab response to protein Ags, that requires the help of CD4 helper T cells?

Answer 7

T-dependent

Question 8

What type of T cell facilitates the formation of germinal centers?

Answer 8

Follicular helper T cells

Question 9

What are germinal centers?

Answer 9

structures generated in secondary lymphoid organs. Several steps of T dependent humoral immune responses occur here

Question 10

Steps of T dependent response:

Answer 10

1. activated B cells differentiate into Ab secreting plasma cells
2. plasma cells migrate from germinal centers (in peripheral lymphoid organs) to bone marrow (where they live for years)
3. long-lived plasma cells continuously secrete Abs that provide immediate protection

Question 11

Ab responses to multivalent non-protein Ags with repeating epitopes (polysaccharides, lipids, nucleic acids) that DO NOT require Ag specific helper T cells, indicate what type of response?

Answer 11

T independent response

Question 12

T independent responses may be elicited by what?

Answer 12

engagement of BCR and may be potentiated by signals from other receptors on the B cells.

Question 13

B cells activated by protein Ags differentiate into what type of cells?

Answer 13

Memory cells

Question 14

Isotype switching and affinity maturation are typically seen in what type of response and in response to what?

Answer 14

humoral immune response; protein Ags

Question 15

What types of signals drive isotype switching and affinity maturation?

Answer 15

T dependent signals

Question 16

Primary or Secondary response? - elicited when the same Ag stimulates B cells, leading to production of greater quantities of specific Abs.

Answer 16

Seconary response

Question 17

Primary or Secondary response? - Naive B cells stimulated by Ag become activated, then differentiate into Ab secreting cells that produce Abs specific for eliciting Ag.

Answer 17

Primary response

Question 18

__________ B cells respond to protein Ags; and initiate ____________ Ab responses.

Answer 18

Follicular; T-dependent

Question 19

T independent responses to multivalent Ags are mediated by what?

Answer 19

marginal zone B cells in the spleen, and B-1 cells in mucosal sites

Question 20

What has to occur to initiate an Ab response?

Answer 20

Ags have to be captured and transported to the B cell areas of lymphoid organs

Question 21

What are most naive B cells? What is another name for them?

Answer 21

follicular B cells (aka recirculating cells)

Question 22

What tissues do follicular B cells migrate into the B cell zones of these tissues?

Answer 22

secondary lymphoid tissues

Question 23

What chemokine guides the movement into lymphoid follicles, and what secretes this chemokine?

Answer 23

CXCL13; secreted by follicular DCs

Question 24

What does chemokine CXCL13 do?

Answer 24

attracts naive B cells into the follicles

Question 25

How are most Ags transported to lymph?

Answer 25

via lymphatic vessels that drain into subcapsular sinus of the LNs

Question 26

Soluble Ags reach B cell zone of follicle and do what?

Answer 26

interact directly with specific B cells

Question 27

Microbes and Ag-Ab complexes are captured by what?

Answer 27

subcapsular sinus macrophages (deliver Ags to follicles)

Question 28

What is captured by resident DCs and transported into follicles, thus activating B cells?

Answer 28

Large Ags