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PHD Block 1, MUSC '13 > 8/29/13 > Flashcards

8/29/13 Flashcards

1
Q

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

A

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

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2
Q

Which antibody is secreted first in the humoral response system?

A

IgM

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3
Q

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

A

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

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4
Q

How can you tell new infections from repeat infections?

A

IgM to IgG ratio–> antibody switch

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5
Q

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

A

No

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6
Q

Describe the B-cell signal transduction pathway

A

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

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7
Q

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

A

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)

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8
Q

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

A

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.

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9
Q

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

A

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

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10
Q

T-helper cell—cytokine—antibody

A

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

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11
Q

Describe how cytokines and CD40L initiate antibody switching

A

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

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12
Q

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

A

Light chain

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13
Q

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

A

Affinity maturation

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14
Q

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

A

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

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15
Q

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

A

FcRIIB

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16
Q

Order of antibodies in serum from highest to lowest

A

G, M, A, E, D

17
Q

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

A

FcRn, expressed in endosomes of the endothelium

18
Q

Which antibody is confined mainly in the blood

A

IgM

19
Q

List the effector function of antibodies

A

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

20
Q

IgA mainly has this type of effector function

A

neutralization

21
Q

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

A

Multiple

22
Q

Fc receptors for opsonization

A

FcgammaRI (high affinity), FcgammaRIIa (low affinity)

23
Q

FcgammeRIIB leads to what

A

down-regulation of B-cells

24
Q

Fc receptor for antibody dependent cellular cytoxcity

A

FcgammaRIIIA

25
Q

FcepsilonRI

A

degranulation of mast cells and basophils

26
Q

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

A

C4b, C2b

27
Q

Which antibody is the best at complement activation?

A

IgM

28
Q

Describe the classical pathway for complement activation

A

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

29
Q

How does Factor I affect complement regulation

A

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

30
Q

How does factor H affect complement regulation

A

It catalyzes the disassociation of C3bBb

31
Q

How does C4 binding protein affect complement regulation?

A

It catalyzes the disassociation of C4bC2b

32
Q

IgA form dimers with the aid of

A

J-chain

33
Q

How does IgA cross in to the lumen

A

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

34
Q

three ways microbes evade humoral immunity

A

Antigenic variation, inhibition of complement, resistance to phagocytosis

PHD Block 1, MUSC '13 (8 decks)

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