BIOL 435 Ch. 11 p.2 (B-Cell Activation, etc.)

Question 1

Ag-induced selection of B-cells with higher affinity

Answer 1

-B-cells that bind, process and present more Ag to T-cells for cytokine assistance =survive!

Question 2

higher affinity B-cells

Answer 2

-may steal Ag from lower-affinity B-cells, promoting their own survival signals

Question 3

isotype or class switching

Answer 3

• occurs soon after Ag contact

- may or may not occur in germinal centres

Question 4

recombination

Answer 4

-results in replacement of an Ab H-chain constant region with a different constant region

Question 5

signals for CSR (class switch recombination)

Answer 5

• B-cells must receive costimulatory signals from CD40 or B-cell TLR in order to engage in CSR
• which cytokine signal is received determines which isotype will be produced
• CSR can occur more than once in a cell

Question 6

most newly generated B-cells

Answer 6

• are lost at the end of the primary immune response

- after Ag is cleared, most effector cells are no longer required

Question 7

apoptotic clearance

Answer 7

-exact mechanism isn’t fully characterized

Question 8

plasma cells

Answer 8

• Ab-secreting cells
• some germinal centre cells mature this way
• around 10 days of ongoing response, interaction between TFH PD-1 receptor and it’s ligands on B-cells

Question 9

homing of plasma cells

Answer 9

• changes in chemokine expression
• to bone marrow=long-lived
• mucosal tissue=produce large amounts of protective IgA

Question 10

memory cells

Answer 10

-generated both witin and outside the GCs

Question 11

outside GCs memory cells

Answer 11

-IgM bearing
-one of first possibilities after Ag stimulation
-generated early in immune response
>prior to onset of SHM in GCs
-results in secretion of non-mutated Abs of lower affinity

Question 12

high-affinity memory B-cells

Answer 12

• generated within GCs starting about 4 days after Ag activation
• class switching from IgM to other Ags occurs
• some remain in or near GCs
• many migrate to sites of Ag drainage (ex. SA marginal zone of spleen)

Question 13

long-lived plamsa cells (LLPC)

Answer 13

-produce Ab long after Ag stimulation
-undergo SHM and affinity maturation
>produce IgG and IgA in mucosa
-not technically memory cells
-provide long-term humoral immunity

Question 14

LLPCs generated

Answer 14

• in the GC after most memory cells have been generated

- then they move out to periphery (bone marrow)

Question 15

T-independent Ag

Answer 15

-stimulate Ab production without need for T-cell help

Question 16

TI-1 Ag

Answer 16

• typically bacterial cells wall components

- bind to innate immunity PRRs on B-cells

Question 17

TI-2 Ag

Answer 17

• polymeric protein Ag and capsular polysaccharides

- crosslink many mIgM BCRs

Question 18

subclasses of B-cells for TI-Ag response

Answer 18

• B-1 B-cells

- Marginal zone B-cells

Question 19

B-1 B-cells

Answer 19

-5% of B-cell population in humans/mice
-primarily produce IgM
-produce ‘natural’ Abs independent of T-cell help
>bind a broad spectrum of Ag with low affinity

Question 20

marginal zone B cells

Answer 20

• must receive low-level signals through BCR for survial
• can renew themselves in the periphery
• differentiate from T2 B-cells in spleen
• specialized to respond to blood-borne Ag entering the immune system through the spleen