Antibodies 2 -Diebel

Question 1

What antibody is always membrane bound?

Answer 1

IgD

Question 2

What Ig’s cross placenta?

Answer 2

IgG only

Question 3

What Ig’s form pentamer and dimer

Answer 3

• IgM forms petamer

- IgA forms dimer

Question 4

What Ig’s function in complement fixation?

Answer 4

Mostly IgM, some IgG

Question 5

Ig that functions in degranulation of Mast cell/basophil?

Answer 5

IgE

Question 6

Ig’s that function in bacterial lysis?

Answer 6

Mostly IgM, some IgG and IgA

Question 7

Ig’s that function in antiviral activity?

Answer 7

Mostly IgA, some IgM and IgG

Question 8

Ig’s that function in toxin neutralization?

Answer 8

– IgG and IgA

Question 9

Ig with highest serum half life?

Highest serum concentration?

Answer 9

IgG (8-23 days)

Most Ig’s in blood are IgG

Question 10

Ig present in mucosal epithelia and bodily secretions?

Answer 10

IgA

Question 11

4 ways we generate antibody diversity?

Answer 11

1. during genetic rearrangement by mixing & matching one of each various gene segments for heavy and light chains
2. Variation incorporated at joining sites for various segments of heavy and light chains
3. Hypermutation in one gene segment druing proliferation of B cells
4. mixing and matching heavy and light chains in combinatorial manner

Question 12

Recombination:

Answer 12

DNA rearranges in developing B cells, to bring one of many V’s together with the correct C so they unit could be copied into mRNA

Question 13

VDJ:

Answer 13

Gene segments V, D, and J on the variable domain region of heavy chain genes.

Question 14

3 gene loci in heavy chain synthesis:

How does light chain synthesis differ?

Answer 14

Variable Domain
Constant Domain
VDJ

Light chain is the same but only have V and J segments, no D. and only one C domain gene.

Question 15

RAG- 1 and 2 function?

Answer 15

Enzymes that do the recombination of antibody and T cell receptor DNA in VDJ segments

knock out these enzymes? - don’t make B or T cells –> Omenn Syndrome

Question 16

TdT? (terminal deoxynucleotidyl transferase )

Answer 16

enzyme that ADDS a few nucleotides randomly.

-Production of V-D and D-J joints are sloppy so it does this to randomize it ==Somatic variation

Question 17

Somatic Variation=

Answer 17

Uses exonucleases to chew away a few nucleotides

TdT enzymes adds a few nucleotides

—>BOOM, more randomization (N region)

Question 18

What is the price of somatic variation/mutation?

Answer 18

Adding/subtracting nucleotides can cause frame-shift mutation –> nonsense or stop codon that stops transcription.

Question 19

Receptor Editing

Answer 19

If you get a frame-shift mutation that stops transcription of heavy or light chain, you try again with other allele (from other parent)

Question 20

Naive B cells express what Ig’s?

Answer 20

IgD and IgM

-this choice occurs at level of PROCESSING of mRNA (so cell can express both)

Question 21

What happens when binds antigen and is activated?

Answer 21

Switch to secretory IgM

-Switch occurs at level of processing of mRNA transcripts

Question 22

So the B cell keeps dividing and differentiate but a T cell comes over an is like “Don’t freak out…..but we’ve got a parasite in here.”
And B cell says…….

Answer 22

“Hey, I can do some class switching to handle this worm better!” –switches to IgE

Point of the story: ***last switches occur at level of REARRANGEMENTS of DNA.

Question 23

Somatic Hypermutation 
How? 
What? 
When? Where? 
Why?

Answer 23

Only in B cells –AFTER antigenic stimulation
How: Activation-Induced Deaminase (AID) enzyme converts C –> U ==slightly different antibodies.

Might make binding better or worse. We are just trying some stuff out.

Question 24

AID enzyme:

Answer 24

In somatic hypermutation– converts some cytosines to uracil randomly in CDR regions.

Question 25

Affinity Maturation:

Answer 25

Find the antibody that has the best AFFINITY to antigen after we make these little changes after antigenic stimulation.

Question 26

Class Switching:

Answer 26

By DNA rearrangement (loop out mu and delta), change to production of IgG (maybe IgE or IgA) –requires help of T cell.

• **C region of H chain only thing to change
• L chain and VH domain stays the same

Question 27

Proliferating cytokines released from Th cells to act on B cells?

Answer 27

IL-2
IL-4
IL-5

Question 28

Cytokines that induce class switch to IgE?

Answer 28

IL-4

IL-5

Question 29

cytokines that block class switch to IgE induced by IL-4?

Answer 29

IFN-gamma

Question 30

Proliferation cytokines?

Answer 30

IL-2
IL-4
IL-5

Question 31

Differentiation cytokines

Answer 31

IL-2
IL-4
IL-5
INF-gamma
TGF-beta

Question 32

Class switching cytokines?
IFN-gamma–> ?

IL-4–> ? , ?

IL-5 —> ?

Answer 32

IFN-gamma —> IgG2a

IL-4 —> IgG1, IgE

IL-5 —> IgE