Diebel Antibodies Part 2

Question 1

What do greek letters:

mu

alpha

gamma

epsilon

delta

refer to respectively?

Answer 1

The constant domains of:

IgM

IgA

IgG

IgE

IgD

Question 2

What do greek letters:

kappa and lamda refer to respectively?

Answer 2

The two possible types of constant regions of light chain.

Question 3

List Ig’s in order of serum half-life length from longest to shortest:

Answer 3

IgG 8-23 days **only one that crosses placenta

IgA 6 days

IgM 5 days

IgD 3 days

IgE 2.5 days

Question 4

Antibody isotypes that fix complement:

Answer 4

IgM …… a lot

IgG ……. a little

Question 5

Antibody isotype that causes degranulation of mast cells and basophils:

Answer 5

IgE

Question 6

Antibody isotypes that cause bacterial lysis:

Answer 6

IgM ….. a lot

IgG and IgA …… a little

Question 7

Antibody isotypes that have antiviral activity:

Answer 7

IgA……. a lot

IgM and IgG ….. a little

Question 8

Antibody isotypes that neutralize toxins:

Answer 8

IgG and IgA

Question 9

Functions of IgM:

Answer 9

• Good at virus neutralization
• Poor at toxin neutralization
• Excellent at bactericidal activity
• Excellent at causing agglutination of antigens
• Excellent at causing precipitation of antigens
• Excellent at complement fixation
• Does not bind to macrophage Fc receptors
• As a monomer it can serve as a surface receptor for antigens on B cells (like IgD)
• Elevated levels indicate a recent infection or other exposure to antigen
• Not useful for protecting immunocompromised individuals
• Not present in interstitial fluids (too big)
• Can be present in bodily secretions

Question 10

Functions of IgG:

Answer 10

• Good at virus neutralization
• Excellent at toxin neutralization
• Good at bactericidal activity
• Good at causing agglutination of antigens
• Good at causing precipitation of antigens
• Good at complement fixation
• Binds to macrophage Fc receptors
• Crosses placenta providing protection to the fetus.
• Can mediate hemolytic disease of the newborn (blue baby syndrome, Rh mismatch)
• Can be used for protecting immunocompromised individuals (gamma globulin)
• Can be used as a blocking antibody to block TNF production (rheumatoid arthritis)
• Can be used as a blocking antibody to block allergens (desensitization to hypersensitivity)
• Not present in most bodily secretions
• Present in interstitial fluids

Question 11

Functions of IgA:

Answer 11

• Excellent at virus neutralization
• Excellent at toxin neutralization
• Good at bactericidal activity
• Good at causing agglutination of antigens
• Good at causing precipitation of antigens
• Does not bind to macrophage Fc receptors
• Daily production of IgA is greater than any other Ig
• B cells that produce IgA migrate to the subepithelial tissue of most mucosal epithelia and of glandular epithelia
• Present in bodily secretions
• Present at very high levels in colostrum and present in breast milk. Provides an excellent level of protection of newborns against respiratory and intestinal infections.

Question 12

Functions of IgE:

Answer 12

• Cross-linking of IgE molecules on the surface of a mast cell or basophil causes the release of histamine; the synthesis of prostaglandins, leukotrienes, and other chemokines and cytokines
• IgE plays a major role in combating parasitic infections
• IgE plays a role in combating pulmonary fungal infections
• Individuals who express allergies to certain antigens over-produce IgE to those antigens.
  - This causes a high level of expression of IgE with the same paratopes (recognize the same epitope on an antigen) on given mast cells. This makes it easier to cross-link two IgE molecules.
  - When antigen is present, many mast cells are degranulated, resulting in an over-stimulation of the immune system that is manifested as an allergic reaction (Type 1 hypersensitivity)
• IgE also plays a role in asthma.

Question 13

Quick description of the Clonal Selection Theory:

Answer 13

Basically the body has billions of antibodies pre-existing before contact with an antigen and when an antigen shows up it runs into a bunch of them before finding the one it fits with with adequate affinity. THEN, that cell replicates itself making more of that antibody.

Question 14

Three regions of DNA that make up heavy chain variable domains?

Answer 14

V, D, J

*original genome has lots of each but only one of each is brought together for transcription

Question 15

Variable light chains have which two DNA segments to chose from for transcription?

Answer 15

V, J

Question 16

First step in getting ready to transcribe a heavy chain?

Answer 16

Combining a D and J.

Question 17

Second step in preparation for heavy chain transcription?

Answer 17

Adding a V to the DJ to make a VDJ

Question 18

Third step in preparation for transcribing heavy chain?

Answer 18

Adding the constant domain of mu to the VDJ

**later delta is added too

Question 19

How does a light chain get transcribed?

Answer 19

Similar to heavy but only V and J used and one C (either lamda OR kappa…not both)

Question 20

Enzymes that do the splicing in DNA recombination of heavy and light chains?

Answer 20

RAG 1 and 2

Question 21

What happens if no RAG is present?

Answer 21

No B-cells or T-cells get made…

Omenn Syndrome

Question 22

What is Somatic variation in gene splicing of antibodies?

Answer 22

The production of the V-D and D-J joints are ‘sloppy.’ The cell has randomizing mechanisms:

First, exonucleases can chew away a few nucleotides after the DNA is cut but before two gene segments (D to J, V to DJ) are joined.

Second, the cell can add a few nucleotides as well with an enzyme called terminal deoxynucleotidyl transferase (TdT) which doesn’t use a template so its additions are random.

Question 23

Enzyme that adds random nucleotides to either end of V-D and D-J junctions.

Answer 23

TdT (terminal deoxynucleotidyl transferase)

***causes frame shift and missence chain termination 2/3 of the time, but big randomness

Question 24

Although a B cell tries to rearrange each allele just once, when a rearrangement is detected as faulty (say a stop codon is generated), or when an anti-self receptor has been displayed, if the recombinases (RAG genes) are still active it can ‘try again.’ Sometimes this results in a successful cell. The process is called?

Answer 24

Receptor editing

Question 25

When do B-cells switch from membrane bound IgD and IgM to secretory IgM?

How does this happen?

Answer 25

After activation be an antigen

Processing of mRNA transcript

Question 26

Final switches to IgE, IgG, IgM, or IgA occur at the level of?

Answer 26

rearrangement of DNA

Question 27

Explain hypermutation and affinity maturation fo antibodies.

Answer 27

the “sloppy” rearrangement AFTER exposure to antigen creates slightly different daughter cells and the ones that bind a little better are more likely to divide again an produce daughter cells with even better affinity for that antigen.

Question 28

What converts random cytosines in the CDR gene regions to uracil?

What does this mean?

Answer 28

Activation-Induced (Cytidine) Deaminase (AID)

So a C:G pair becomes a uracil: guanine mismatch. The uracil bases are excised by the repair enzyme uracil-DNA glycosylase. Error-prone DNA polymerases then fill
in the gap, creating mostly single-base substitution mutations, so at the end of cell division one daughter may be making a different (worse? better?) antibody

Question 29

What is class switching?

Answer 29

Activated cell swaps mu for gama, epsilon, or alpha Fc DNA (but keeps the SAME VDJ/VJ). Mu info is gone forever.

Question 30

Proliferation cytokines =

Answer 30

IL-2, IL-4, IL-5

Question 31

Differentiation cytokines =

Answer 31

IL-2, IL-4, IL-5, IFN-γ, and TGF-β

Question 32

Class switching cytokines=

Answer 32

IFN-γ –>IgG2a

IL-4 –> IgG1, IgE

IL-5 –> IgE