W5: B cells

Question 1

Secondary follicle is located in the __ __ of lymph node, the site of B cell maturation.

Answer 1

germinal center

Question 2

B cell mechanisms for making Abs

Answer 2

Somatic recombination

Random nucleotide insertion at joints

Isotype switching

Somatic hypermutation

Question 3

Mechanism for diverse Ab production:

Combinatorial diversity

Junctional diversity

Class diversity

Binding site diversity

Answer 3

Combinatorial diversity (somatic recombination; VDJ)

Junctional diversity (random nucleotide insertion at joints)

Class diversity (Fc isotype switching)

Binding site diversity (somatic hypermutation)

Question 4

Function of enzymes and location:

Rag-1, Rag-2
TdT
AID

Answer 4

Rag-1, Rag-2: VDJ (BM)

TdT: random nucleotide insertion at joints (BM)

AID: isotype switching (Fc) and somatic hypermutation (Fv) (LN)

Question 5

RAG-1 and RAG-2 mediate __ by cutting DNA and bringing 2 ends together

This happens in __.

Answer 5

VDJ recombination;

bone marrow

Question 6

TdT enzyme mediates __ diversity.

This happens in __.

Answer 6

junctional;

bone marrow

Question 7

AID enzyme mediates __ and __ diversity in the __.

Answer 7

class (Fc) and binding site (Fv) diversity, LN

Question 8

Tfh cells activate B cell at the __, where they recognize the same antigen.

Answer 8

germinal center

Question 9

Tfh cells allow B cells to survive and proliferate in __.

Answer 9

germinal center

Question 10

Tfh cells mediate __ and __ diversity in B cells in the germinal center (organ).

Enzyme?

Answer 10

class diversity (isotype switching), binding site diversity (somatic hypermutation)

organ - LN
enzyme - AID

Question 11

Tfh cell and enzyme __ mediate class switching in B cells.

Answer 11

AID

Question 12

Polyclonal antibody response is mediated by __ __ (binding site diversity).

Answer 12

somatic hypermutation

many Ab target same antigen

Question 13

What allows transmembrane BCR to become secreted as Ab (Ig)?

Answer 13

RNA splicing

Question 14

plasma cells differentiate in __.

Answer 14

LN (germinal center)

Question 15

Secreted Ab function: (which Ab)

Neutralization
Opsonization
Complement fixation

Answer 15

Neutralization (A,G)
Opsonization (G,E)
Complement fixation (G,M)

NAG
GEO
Fix GM car

Question 16

First exposure to pathogen: initial response is always by __.

Secondary response is always faster and higher-level by __.

Answer 16

IgM

IgG

Question 17

Multimers are formed by __ and __

Answer 17

IgA (dimeric), IgM (pentameric)

Question 18

Which secreted Ab found here?

plasma

mucosal surfaces

Answer 18

plasma: IgG»>IgM>IgA>IgE

mucosal surfaces: IgA

Question 19

Ab found on mucosal surfaces

Answer 19

IgA

Question 20

Diagnostic: presence of __ Ab means acute infection.

Answer 20

IgM

Question 21

Presence of Ab __ means there was a past exposure (memory).

Answer 21

IgG

Question 22

Failure to class switch from IgM to other Ab

Answer 22

Hyper IgM Syndrome

Question 23

Hyper IgM Syndrome results in

Answer 23

recurrent bacterial infections (only IgM; no germinal center)

T cell defect prevents B cell maturation