8/29/13

Question 1

What is the difference in antibody location between a naive B-cell and a mature B-cell?

Answer 1

Naive B-cells have antibodies on their cell surface while mature B-cells secrete antibodies

Question 2

Which antibody is secreted first in the humoral response system?

Answer 2

IgM

Question 3

What are the 3 subsets of B-cells and what do they respond to?

Answer 3

Follicular B-cells–> they respond to protein antigens and are the source of antibodies to T-cell dependent protein antigens
Marginal Zone B-cells–>Blood borne Non-protein antigens
B-1 cells–> Non-protein antigens in the mucosa and peritoneum

Question 4

How can you tell new infections from repeat infections?

Answer 4

IgM to IgG ratio–> antibody switch

Question 5

For B-cell activation, does the antigen have to be processed?

Answer 5

No

Question 6

Describe the B-cell signal transduction pathway

Answer 6

Accessory molecules Ig alpha and Ig beta contain ITAM–> cluster together when antigen is attached–> ITAM phosphorylated–> BLK/Lyn/Fyn phosphorylated–> Syk phosphorylated that leads to the activation of the PLC pathway and RAS/RAC pathway described for T-cells

Question 7

Which molecules of B-cells are synonymous with CD28 and CD40L?

Answer 7

CR2 and TLR–> stimulate activity but do not participate in the signal cascade like accessory moclecules (CD3, zeta for Tcells/Ig alpha, Ig beta for B-cells)

Question 8

How do T-cells and B-cells come to interact with each other in lymph nodes?

Answer 8

CD4 T-cells switch from CCR7 to CXCR5 when activated and thus migrate towards the follicle. B-cells switch from CXCR5 to CCR7 when they are activated and thus move outside the follicle. The T-cells and B-cells meet just outside the follicle.

Question 9

What are the helper T-cell signals that confer antibody switching in B-cells?

Answer 9

CD40L signal to switch and cytokines signal which isotype to switch to (germinal center reactions)

Question 10

T-helper cell—cytokine—antibody

Answer 10

TH1—IFNgamma—IgG1 and IgG3
TH2—IL-4— IgE
TH17— TGB beta, BAFF—IgA

Question 11

Describe how cytokines and CD40L initiate antibody switching

Answer 11

Cytokines initiate RNA transcription at one of the S regions–> CD40L induced enzyme AID can act on the more open conformation

Question 12

Which chain stays constant during antibody switching (Heavy chain, light chain)

Answer 12

Light chain

Question 13

The reason average affinity of Ab increases with repeated exposures to T-dependent antigens

Answer 13

Affinity maturation

Question 14

What is the difference between non protein and protein antigen in B-cell stimulation

Answer 14

Non-protein antigen does not stimulate Ab switching, affinity maturation, or memory cells

Question 15

Which receptor on B-cells stimulates humoral response down-regulation?

Answer 15

FcRIIB

Question 16

Order of antibodies in serum from highest to lowest

Answer 16

G, M, A, E, D

Question 17

What receptor helps extend the half life of IgG antibodies and where are they expressed throughout life?

Answer 17

FcRn, expressed in endosomes of the endothelium

Question 18

Which antibody is confined mainly in the blood

Answer 18

IgM

Question 19

List the effector function of antibodies

Answer 19

Neutralization of toxins, Opsonization, antibody dependent cellular cytotoxicity, complement activation (lysis, opsonization, and inflammation)

Question 20

IgA mainly has this type of effector function

Answer 20

neutralization

Question 21

Multiple/ single FCr on the phagocytes must be engaged by Fc portions of antibodies for successful opsonization

Answer 21

Multiple

Question 22

Fc receptors for opsonization

Answer 22

FcgammaRI (high affinity), FcgammaRIIa (low affinity)

Question 23

FcgammeRIIB leads to what

Answer 23

down-regulation of B-cells

Question 24

Fc receptor for antibody dependent cellular cytoxcity

Answer 24

FcgammaRIIIA

Question 25

FcepsilonRI

Answer 25

degranulation of mast cells and basophils

Question 26

In the classical pathway of complement recognition, what are the components of the C3 convertase?

Answer 26

C4b, C2b

Question 27

Which antibody is the best at complement activation?

Answer 27

IgM

Question 28

Describe the classical pathway for complement activation

Answer 28

C1q binds to two or more antibodies--> reveals binding sight for C1r and C1s--> C4 binds to C1q and is cleaved by C1r2s2--> C4b binds to the antigenic surface and antibodies-->C2 binds to C4b and is cleaved by C1s making C2b--> C3 convertase cleaves C3 to C3b--> C3b binds to the convertase and antigen sruface--> the complex cleaves C5 and leads to MAC formation

Question 29

How does Factor I affect complement regulation

Answer 29

It cleaves C3b to C3bi (cofactor is factor H) and converts C4b to C4bi with C4 binding protein as cofactor

Question 30

How does factor H affect complement regulation

Answer 30

It catalyzes the disassociation of C3bBb

Question 31

How does C4 binding protein affect complement regulation?

Answer 31

It catalyzes the disassociation of C4bC2b

Question 32

IgA form dimers with the aid of

Answer 32

J-chain

Question 33

How does IgA cross in to the lumen

Answer 33

Dimer forms--> Poly Ig receptor at Fc-->IgA dimer cleaved and actively transported to lumenal side--> secretory component remains on the lumenal side

Question 34

three ways microbes evade humoral immunity

Answer 34

Antigenic variation, inhibition of complement, resistance to phagocytosis