B Cell-Mediated Immunity

Question 1

where do B cells under go negative selection?

Answer 1

in the bone marrow

Question 2

where do B cells under go positive selection?

Answer 2

secondary lymphoid tissues

Question 3

where are B cells activated?

Answer 3

in the peripheral lymphoid tissues (secondary LT)

Question 4

what are the two types of effector B cells?

Answer 4

memory and plasma cell

Question 5

once a B cell is a plasma cell can it revert back to a B cell?

Answer 5

NO!!!!j

Question 6

what chemokine attracts B cells to the primary follicle?

Answer 6

CXCL 13

Question 7

what chemokine attract B B cells to the HEV?

Answer 7

CCL 21 and CCL19

Question 8

where do B cells interact with FDCs?

Answer 8

in the primary follicle

Question 9

what cells present antigen to B cells?

Answer 9

macs and FDCs

Question 10

what does B cell activation drive?

Answer 10

clonal expansion
class switching
SMH

Question 11

what are follicular dendritic cells?

Answer 11

stromal cells involved in B cell development and activation

• accumulate antigens via complement receptors
• NO phagocytic activity NOT a classical DC

Question 12

what is the receptor for bound complement to antigen on macs and FDCs

Answer 12

CR2

Question 13

what are the three signals for B cell activation?

Answer 13

antibody crosslinking
co-receptor signaling
cytokines

Question 14

what two signals are requisite for B cell activation?

Answer 14

antibody crosslinking
co-receptor signaling
*without it the B cell becomes anergic

Question 15

what does antibody crosslinking do?

Answer 15

activates

Question 16

what does co-receptor signaling do?

Answer 16

survival and proliferation

Question 17

what are the two types of antigens a B cell can be activated by?

Answer 17

thymus dependent

thymus independent

Question 18

thymus dependent antigens

Answer 18

protein
protein-assosicated antigen
Tfh cell interaction required
expressed via MHC II

Question 19

thymus independnt antigens

Answer 19

PRR-detected (TLRs)
compliment bound antigen
lipids, carbs, toxins

Question 20

Signal 1: antibody crosslinking

Answer 20

clustering and aggregation
Ig alpha and beta signaling
*does not tell B cell if the antigen is self or not, it just activates

Question 21

Signal 2: B cell co-receptor signaling

Answer 21

**ensures target is pathogenic**
prevents angery
foreign or self antigen
clonal expansion
1. B cell co-receptor complex (binds to complement)
2. PRRs
3. CD40

Question 22

Signal 3: cytokine signaling

Answer 22

Tfh are most common source of cytokines, but local cytokines can provide signals if T cells are gone

Question 23

four roles of cytokine signaling

Answer 23

survival and proliferation
class switching
SMH
differentiation

Question 24

what is a cognate pair?

Answer 24

when activated B and Tfh cells come together at the follicle boundary
*B cell is presenting the antigen via MHC II

Question 25

how to Tfh cells aid in B cell activation

Answer 25

CD40 induces survival and proliferation (co-receptor signal) - release cytokines - induces differentiation and isotype switching

Question 26

where do cognate pairs go first and what happens there?

Answer 26

* primary focus - here the plasma cells just produce IgM to prevent systemic infection * *no class-swithing or somatic hympermutation

Question 27

After the cognate pair leaves the primary focus where do they go?

Answer 27

the secondary focus, which forms the germinal center

Question 28

what happens at the secondary focus?

Answer 28

enormous proliferation to produce plasma and memory cells - class switching and SMH - selection of most specific plasma cells

Question 29

what is a centroblast?

Answer 29

come after the congate pair gets to germinal center - proliferating source of new B cells - NO Igs on surface - SMH - class switching - create centrocytes

Question 30

what is a centrocyte

Answer 30

divide slowly - express surface Ig - cannot class switch or SMH - interact and selected for by FDCs - programmed to die

Question 31

what is class switching

Answer 31

RAG proteins reactivated in centroblast change heavy chain cytokine induced classes dictate effector function

Question 32

what is somatic hypermutation

Answer 32

``` directed hypervariable region mutation single nucleotide insertions and subs produces new epitope binding region as centroblasts divide a mutation is introduced increases Ab affinity paired with selection process ```

Question 33

what cell selects for high-affinity centrocytes?

Answer 33

FDCs, | *the Abs are required to compete to get the highest affinity Abs produced

Question 34

what happens to FDC-bound centrocytes?

Answer 34

Tfh cells bind and give survival signal and further proliferation -differentiation into plasma and memory B cells

Question 35

what are the four broad effector functions for antibodies

Answer 35

neutralization opsonization complement fixation Antibody-Dependent Cell-mediated cytotoxicity (ADCC)

Question 36

why are Fc receptors important?

Answer 36

allow adaptive specificity to innate cells by binding to the antigen bound antibody

Question 37

what are the functions of Fc receptors?

Answer 37

``` stimulate and inhibitor function -cytokine production/release -phagocytosis -degranulation -targeted killing involved in Ig transport IgG, IgE, IgA ```

Question 38

what receptor transports IgG across membranes

Answer 38

FcRn

Question 39

what is poly-Ig receptor?

Answer 39

binds the the Fc portion of the dimeric IgA to transport to mucosal surfaces

Question 40

what Igs generally neutralize?

Answer 40

IgA and IgG

Question 41

what cells clear agglutinized antigens?

Answer 41

erythrocytes -they bind complement on antigens that are bound by Abs and deliver them to Macs which have Fc receptors and allow the agglutinized antigen to be killed

Question 42

what are IgEs

Answer 42

cell surface receptors for mast, basophils, eosinophils - targeted degranulation - important in allergies

Question 43

which two Abs initiate complement?

Answer 43

IgG and IgM

Question 44

Antibodies provide passive immunity during development how?

Answer 44

IgG during gestation IgA from breast milk mother's immunity passed to child