Humoral immune Response

Question 1

what are the Co-BCRs on a mature naive B cell

Answer 1

CD19, CD81, CR2 (CD21)

Question 2

what surface markers does a mature naive B cell express

Answer 2

CD40, CD20, CD19

Question 3

what surface marker does a Activated Mature B cell express

Answer 3

CD45R

Question 4

what are B2 cells

Answer 4

follicular B cells; re-circulating B cells and majority of B cells

Question 5

what are B1 cells

Answer 5

marginal B cells in spleen, recognize non-protein Ag and blood-borne polysaccharide Ag; secrete IgM

Question 6

what is CXCR5

Answer 6

B cell chemokine receptor

Question 7

CXCR5 expressed on HEV allows LFA-1 to bind to what on B cell and change to high affinity

Answer 7

ICAM

Question 8

naive B cells migrate to the follicular area and interact with what cell

Answer 8

Follicular Dendritic Cell

Question 9

what is the first signal in B-cell activation and is this sufficient to activate naive B-cells into activated mature B-cells

Answer 9

Cross-linking of BCR by Ag; signal is NOT sufficient to active naive B cells

Question 10

Ag with bound C3d complement recognized by membrane Igs on Bcell bind to what B-cell receptor?

Answer 10

CR2 (CD21)

Question 11

what are 3 ways to get first signal?

Answer 11

1. crosslinking 2+ BCRs
2. BCR and CR2 receptor engagement thru C3d bound to Ag.
3. BCR and Toll-like receptors (TLR)

Question 12

C3d complement bound to Ag makes it how much more immunogenic (will elicit immune response)

Answer 12

1000x more

Question 13

what are the outcomes of the First signal in B-cell activation

Answer 13

small secretion of IgM
upregulate anti-apoptotic proteins (Bcl-2)
upregulate HLA Class 2 and B7
CCR7 expression increased (t-cell chemokine)
CXCR5 = B cell chemokine

Question 14

for the T-dependent Ag activation of B-cells what is the main co-stimulatory signal needed? What does this binding cause?

Answer 14

CD40 (Bcell) binds CD40L (Tcell)

CD40 binding CD40L –> stimulates B7 production in Bcell which binds CD28 on Tcell

also stimulates AID enzyme

Question 15

What is the AID enzyme? How is it upregulated

Answer 15

AID enzyme is necessary for affinity maturation and class switching

is upregulated when CD40:CD40L binding occurs

Question 16

what signals are necessary for Class Switching?

Answer 16

AID enzyme
CD40:CD40L

Tfh cells

Question 17

where does proliferation of B cells occur?

Answer 17

germinal centers

Question 18

what surface markers do T-follicular helper cells (Tfh) express

Answer 18

CD4 and low levels of CD25

Question 19

where does class switching occur

Answer 19

Germinal Centers

Question 20

what on Tfh cells binds to activated B cells

Answer 20

ICOS (Tfh) binds ICOS-L (Bcell)

Question 21

class switching occurs in what chain?

Answer 21

Heavy chain

Question 22

What does IL-21 do? Where does it come from

Answer 22

produced by Tfh cells

facilitates differentiation to plasmablasts –> Abs produced

Question 23

in the T-dependent Ag activation of B cells the binding of CD40:CD40L and AID enzyme causes what Ig?

Answer 23

IgG

Question 24

TGF-beta from Tcells, Bcells, DC promotes what class switching

Answer 24

IgA

Question 25

IL-4 promotes what class switching

Answer 25

IgE, IgG4, and some IgA

Question 26

what does AID enzyme do?

Answer 26

converts C's to U's by deamination --> allowing Ape I endonuclease to create double-stranded breaks in DNA
which allows for affinity maturation and class switching

Question 27

Plasma cells have decreased what markers and increased what?

Answer 27

decreased: CD19 (Co-BCR), CD20, HLA II
increased: CD27

Question 28

memory B cells express what surface marker and what anti-apoptotic protein?

Answer 28

CD27, CD45 (O)

Bcl-2 anti-apoptotic protein

Question 29

Memory B cells receive additional what IL-? from stromal cells?

Answer 29

IL-7

Question 30

What Ig shuts down B-cells so they can’t produce Antibodys? And what does it bind to in order to perform this function

Answer 30

IgG

binds to Fc-gamma-IIb receptor which binds ITIM ==> PIP3 converted back to PIP2 => INHIBITS